qemu-e2k/block/mirror.c

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mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
/*
* Image mirroring
*
* Copyright Red Hat, Inc. 2012
*
* Authors:
* Paolo Bonzini <pbonzini@redhat.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "trace.h"
#include "block/blockjob.h"
#include "block/block_int.h"
#include "sysemu/block-backend.h"
#include "qapi/qmp/qerror.h"
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
#include "qemu/ratelimit.h"
#include "qemu/bitmap.h"
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
#define SLICE_TIME 100000000ULL /* ns */
#define MAX_IN_FLIGHT 16
#define DEFAULT_MIRROR_BUF_SIZE (10 << 20)
/* The mirroring buffer is a list of granularity-sized chunks.
* Free chunks are organized in a list.
*/
typedef struct MirrorBuffer {
QSIMPLEQ_ENTRY(MirrorBuffer) next;
} MirrorBuffer;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
typedef struct MirrorBlockJob {
BlockJob common;
RateLimit limit;
BlockDriverState *target;
BlockDriverState *base;
/* The name of the graph node to replace */
char *replaces;
/* The BDS to replace */
BlockDriverState *to_replace;
/* Used to block operations on the drive-mirror-replace target */
Error *replace_blocker;
bool is_none_mode;
BlockdevOnError on_source_error, on_target_error;
bool synced;
bool should_complete;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
int64_t sector_num;
int64_t granularity;
size_t buf_size;
int64_t bdev_length;
unsigned long *cow_bitmap;
BdrvDirtyBitmap *dirty_bitmap;
HBitmapIter hbi;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
uint8_t *buf;
QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
int buf_free_count;
unsigned long *in_flight_bitmap;
int in_flight;
int sectors_in_flight;
int ret;
bool unmap;
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
bool waiting_for_io;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
} MirrorBlockJob;
typedef struct MirrorOp {
MirrorBlockJob *s;
QEMUIOVector qiov;
int64_t sector_num;
int nb_sectors;
} MirrorOp;
static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
int error)
{
s->synced = false;
if (read) {
return block_job_error_action(&s->common, s->common.bs,
s->on_source_error, true, error);
} else {
return block_job_error_action(&s->common, s->target,
s->on_target_error, false, error);
}
}
static void mirror_iteration_done(MirrorOp *op, int ret)
{
MirrorBlockJob *s = op->s;
struct iovec *iov;
int64_t chunk_num;
int i, nb_chunks, sectors_per_chunk;
trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret);
s->in_flight--;
s->sectors_in_flight -= op->nb_sectors;
iov = op->qiov.iov;
for (i = 0; i < op->qiov.niov; i++) {
MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;
QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);
s->buf_free_count++;
}
sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
chunk_num = op->sector_num / sectors_per_chunk;
nb_chunks = op->nb_sectors / sectors_per_chunk;
bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
if (ret >= 0) {
if (s->cow_bitmap) {
bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
}
s->common.offset += (uint64_t)op->nb_sectors * BDRV_SECTOR_SIZE;
}
qemu_iovec_destroy(&op->qiov);
g_free(op);
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
if (s->waiting_for_io) {
qemu_coroutine_enter(s->common.co, NULL);
}
}
static void mirror_write_complete(void *opaque, int ret)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
if (ret < 0) {
BlockErrorAction action;
bdrv_set_dirty_bitmap(s->dirty_bitmap, op->sector_num, op->nb_sectors);
action = mirror_error_action(s, false, -ret);
if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
s->ret = ret;
}
}
mirror_iteration_done(op, ret);
}
static void mirror_read_complete(void *opaque, int ret)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
if (ret < 0) {
BlockErrorAction action;
bdrv_set_dirty_bitmap(s->dirty_bitmap, op->sector_num, op->nb_sectors);
action = mirror_error_action(s, true, -ret);
if (action == BLOCK_ERROR_ACTION_REPORT && s->ret >= 0) {
s->ret = ret;
}
mirror_iteration_done(op, ret);
return;
}
bdrv_aio_writev(s->target, op->sector_num, &op->qiov, op->nb_sectors,
mirror_write_complete, op);
}
static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
{
BlockDriverState *source = s->common.bs;
int nb_sectors, sectors_per_chunk, nb_chunks;
int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
uint64_t delay_ns = 0;
MirrorOp *op;
int pnum;
int64_t ret;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
s->sector_num = hbitmap_iter_next(&s->hbi);
if (s->sector_num < 0) {
bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
s->sector_num = hbitmap_iter_next(&s->hbi);
trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap));
assert(s->sector_num >= 0);
}
hbitmap_next_sector = s->sector_num;
sector_num = s->sector_num;
sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
end = s->bdev_length / BDRV_SECTOR_SIZE;
/* Extend the QEMUIOVector to include all adjacent blocks that will
* be copied in this operation.
*
* We have to do this if we have no backing file yet in the destination,
* and the cluster size is very large. Then we need to do COW ourselves.
* The first time a cluster is copied, copy it entirely. Note that,
* because both the granularity and the cluster size are powers of two,
* the number of sectors to copy cannot exceed one cluster.
*
* We also want to extend the QEMUIOVector to include more adjacent
* dirty blocks if possible, to limit the number of I/O operations and
* run efficiently even with a small granularity.
*/
nb_chunks = 0;
nb_sectors = 0;
next_sector = sector_num;
next_chunk = sector_num / sectors_per_chunk;
/* Wait for I/O to this cluster (from a previous iteration) to be done. */
while (test_bit(next_chunk, s->in_flight_bitmap)) {
trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = true;
qemu_coroutine_yield();
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = false;
}
do {
int added_sectors, added_chunks;
if (!bdrv_get_dirty(source, s->dirty_bitmap, next_sector) ||
test_bit(next_chunk, s->in_flight_bitmap)) {
assert(nb_sectors > 0);
break;
}
added_sectors = sectors_per_chunk;
if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) {
bdrv_round_to_clusters(s->target,
next_sector, added_sectors,
&next_sector, &added_sectors);
/* On the first iteration, the rounding may make us copy
* sectors before the first dirty one.
*/
if (next_sector < sector_num) {
assert(nb_sectors == 0);
sector_num = next_sector;
next_chunk = next_sector / sectors_per_chunk;
}
}
added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors));
added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk;
/* When doing COW, it may happen that there is not enough space for
* a full cluster. Wait if that is the case.
*/
while (nb_chunks == 0 && s->buf_free_count < added_chunks) {
trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = true;
qemu_coroutine_yield();
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = false;
}
if (s->buf_free_count < nb_chunks + added_chunks) {
trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
break;
}
if (IOV_MAX < nb_chunks + added_chunks) {
trace_mirror_break_iov_max(s, nb_chunks, added_chunks);
break;
}
/* We have enough free space to copy these sectors. */
bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);
nb_sectors += added_sectors;
nb_chunks += added_chunks;
next_sector += added_sectors;
next_chunk += added_chunks;
if (!s->synced && s->common.speed) {
delay_ns = ratelimit_calculate_delay(&s->limit, added_sectors);
}
} while (delay_ns == 0 && next_sector < end);
/* Allocate a MirrorOp that is used as an AIO callback. */
op = g_new(MirrorOp, 1);
op->s = s;
op->sector_num = sector_num;
op->nb_sectors = nb_sectors;
/* Now make a QEMUIOVector taking enough granularity-sized chunks
* from s->buf_free.
*/
qemu_iovec_init(&op->qiov, nb_chunks);
next_sector = sector_num;
while (nb_chunks-- > 0) {
MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
size_t remaining = (nb_sectors * BDRV_SECTOR_SIZE) - op->qiov.size;
QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
s->buf_free_count--;
qemu_iovec_add(&op->qiov, buf, MIN(s->granularity, remaining));
/* Advance the HBitmapIter in parallel, so that we do not examine
* the same sector twice.
*/
if (next_sector > hbitmap_next_sector
&& bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) {
hbitmap_next_sector = hbitmap_iter_next(&s->hbi);
}
next_sector += sectors_per_chunk;
}
bdrv_reset_dirty_bitmap(s->dirty_bitmap, sector_num, nb_sectors);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
/* Copy the dirty cluster. */
s->in_flight++;
s->sectors_in_flight += nb_sectors;
trace_mirror_one_iteration(s, sector_num, nb_sectors);
ret = bdrv_get_block_status_above(source, NULL, sector_num,
nb_sectors, &pnum);
if (ret < 0 || pnum < nb_sectors ||
(ret & BDRV_BLOCK_DATA && !(ret & BDRV_BLOCK_ZERO))) {
bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
mirror_read_complete, op);
} else if (ret & BDRV_BLOCK_ZERO) {
bdrv_aio_write_zeroes(s->target, sector_num, op->nb_sectors,
s->unmap ? BDRV_REQ_MAY_UNMAP : 0,
mirror_write_complete, op);
} else {
assert(!(ret & BDRV_BLOCK_DATA));
bdrv_aio_discard(s->target, sector_num, op->nb_sectors,
mirror_write_complete, op);
}
return delay_ns;
}
static void mirror_free_init(MirrorBlockJob *s)
{
int granularity = s->granularity;
size_t buf_size = s->buf_size;
uint8_t *buf = s->buf;
assert(s->buf_free_count == 0);
QSIMPLEQ_INIT(&s->buf_free);
while (buf_size != 0) {
MirrorBuffer *cur = (MirrorBuffer *)buf;
QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next);
s->buf_free_count++;
buf_size -= granularity;
buf += granularity;
}
}
static void mirror_drain(MirrorBlockJob *s)
{
while (s->in_flight > 0) {
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = true;
qemu_coroutine_yield();
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = false;
}
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
typedef struct {
int ret;
} MirrorExitData;
static void mirror_exit(BlockJob *job, void *opaque)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
MirrorExitData *data = opaque;
AioContext *replace_aio_context = NULL;
BlockDriverState *src = s->common.bs;
/* Make sure that the source BDS doesn't go away before we called
* block_job_completed(). */
bdrv_ref(src);
if (s->to_replace) {
replace_aio_context = bdrv_get_aio_context(s->to_replace);
aio_context_acquire(replace_aio_context);
}
if (s->should_complete && data->ret == 0) {
BlockDriverState *to_replace = s->common.bs;
if (s->to_replace) {
to_replace = s->to_replace;
}
if (bdrv_get_flags(s->target) != bdrv_get_flags(to_replace)) {
bdrv_reopen(s->target, bdrv_get_flags(to_replace), NULL);
}
bdrv_replace_in_backing_chain(to_replace, s->target);
}
if (s->to_replace) {
bdrv_op_unblock_all(s->to_replace, s->replace_blocker);
error_free(s->replace_blocker);
bdrv_unref(s->to_replace);
}
if (replace_aio_context) {
aio_context_release(replace_aio_context);
}
g_free(s->replaces);
bdrv_op_unblock_all(s->target, s->common.blocker);
bdrv_unref(s->target);
block_job_completed(&s->common, data->ret);
g_free(data);
bdrv_unref(src);
}
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
static void coroutine_fn mirror_run(void *opaque)
{
MirrorBlockJob *s = opaque;
MirrorExitData *data;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
BlockDriverState *bs = s->common.bs;
int64_t sector_num, end, length;
uint64_t last_pause_ns;
BlockDriverInfo bdi;
char backing_filename[2]; /* we only need 2 characters because we are only
checking for a NULL string */
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
int ret = 0;
int n;
if (block_job_is_cancelled(&s->common)) {
goto immediate_exit;
}
s->bdev_length = bdrv_getlength(bs);
if (s->bdev_length < 0) {
ret = s->bdev_length;
goto immediate_exit;
} else if (s->bdev_length == 0) {
/* Report BLOCK_JOB_READY and wait for complete. */
block_job_event_ready(&s->common);
s->synced = true;
while (!block_job_is_cancelled(&s->common) && !s->should_complete) {
block_job_yield(&s->common);
}
s->common.cancelled = false;
goto immediate_exit;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
length = DIV_ROUND_UP(s->bdev_length, s->granularity);
s->in_flight_bitmap = bitmap_new(length);
/* If we have no backing file yet in the destination, we cannot let
* the destination do COW. Instead, we copy sectors around the
* dirty data if needed. We need a bitmap to do that.
*/
bdrv_get_backing_filename(s->target, backing_filename,
sizeof(backing_filename));
if (backing_filename[0] && !s->target->backing) {
ret = bdrv_get_info(s->target, &bdi);
if (ret < 0) {
goto immediate_exit;
}
if (s->granularity < bdi.cluster_size) {
s->buf_size = MAX(s->buf_size, bdi.cluster_size);
s->cow_bitmap = bitmap_new(length);
}
}
end = s->bdev_length / BDRV_SECTOR_SIZE;
s->buf = qemu_try_blockalign(bs, s->buf_size);
if (s->buf == NULL) {
ret = -ENOMEM;
goto immediate_exit;
}
mirror_free_init(s);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
if (!s->is_none_mode) {
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
/* First part, loop on the sectors and initialize the dirty bitmap. */
BlockDriverState *base = s->base;
bool mark_all_dirty = s->base == NULL && !bdrv_has_zero_init(s->target);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
for (sector_num = 0; sector_num < end; ) {
/* Just to make sure we are not exceeding int limit. */
int nb_sectors = MIN(INT_MAX >> BDRV_SECTOR_BITS,
end - sector_num);
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
if (now - last_pause_ns > SLICE_TIME) {
last_pause_ns = now;
block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, 0);
}
if (block_job_is_cancelled(&s->common)) {
goto immediate_exit;
}
ret = bdrv_is_allocated_above(bs, base, sector_num, nb_sectors, &n);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
if (ret < 0) {
goto immediate_exit;
}
assert(n > 0);
if (ret == 1 || mark_all_dirty) {
bdrv_set_dirty_bitmap(s->dirty_bitmap, sector_num, n);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
sector_num += n;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
}
bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
for (;;) {
uint64_t delay_ns = 0;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
int64_t cnt;
bool should_complete;
if (s->ret < 0) {
ret = s->ret;
goto immediate_exit;
}
cnt = bdrv_get_dirty_count(s->dirty_bitmap);
/* s->common.offset contains the number of bytes already processed so
* far, cnt is the number of dirty sectors remaining and
* s->sectors_in_flight is the number of sectors currently being
* processed; together those are the current total operation length */
s->common.len = s->common.offset +
(cnt + s->sectors_in_flight) * BDRV_SECTOR_SIZE;
/* Note that even when no rate limit is applied we need to yield
* periodically with no pending I/O so that bdrv_drain_all() returns.
* We do so every SLICE_TIME nanoseconds, or when there is an error,
* or when the source is clean, whichever comes first.
*/
if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns < SLICE_TIME &&
s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
(cnt == 0 && s->in_flight > 0)) {
trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = true;
qemu_coroutine_yield();
mirror: Fix coroutine reentrance This fixes a regression introduced by commit dcfb3beb ("mirror: Do zero write on target if sectors not allocated"), which was reported to cause aborts with the message "Co-routine re-entered recursively". The cause for this bug is the following code in mirror_iteration_done(): if (s->common.busy) { qemu_coroutine_enter(s->common.co, NULL); } This has always been ugly because - unlike most places that reenter - it doesn't have a specific yield that it pairs with, but is more uncontrolled. What we really mean here is "reenter the coroutine if it's in one of the four explicit yields in mirror.c". This used to be equivalent with s->common.busy because neither mirror_run() nor mirror_iteration() call any function that could yield. However since commit dcfb3beb this doesn't hold true any more: bdrv_get_block_status_above() can yield. So what happens is that bdrv_get_block_status_above() wants to take a lock that is already held, so it adds itself to the queue of waiting coroutines and yields. Instead of being woken up by the unlock function, however, it gets woken up by mirror_iteration_done(), which is obviously wrong. In most cases the code actually happens to cope fairly well with such cases, but in this specific case, the unlock must already have scheduled the coroutine for wakeup when mirror_iteration_done() reentered it. And then the coroutine happened to process the scheduled restarts and tried to reenter itself recursively. This patch fixes the problem by pairing the reenter in mirror_iteration_done() with specific yields instead of abusing s->common.busy. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Message-id: 1439455310-11263-1-git-send-email-kwolf@redhat.com Signed-off-by: Jeff Cody <jcody@redhat.com>
2015-08-13 10:41:50 +02:00
s->waiting_for_io = false;
continue;
} else if (cnt != 0) {
delay_ns = mirror_iteration(s);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
}
should_complete = false;
if (s->in_flight == 0 && cnt == 0) {
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
trace_mirror_before_flush(s);
ret = bdrv_flush(s->target);
if (ret < 0) {
if (mirror_error_action(s, false, -ret) ==
BLOCK_ERROR_ACTION_REPORT) {
goto immediate_exit;
}
} else {
/* We're out of the streaming phase. From now on, if the job
* is cancelled we will actually complete all pending I/O and
* report completion. This way, block-job-cancel will leave
* the target in a consistent state.
*/
if (!s->synced) {
block_job_event_ready(&s->common);
s->synced = true;
}
should_complete = s->should_complete ||
block_job_is_cancelled(&s->common);
cnt = bdrv_get_dirty_count(s->dirty_bitmap);
}
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
if (cnt == 0 && should_complete) {
/* The dirty bitmap is not updated while operations are pending.
* If we're about to exit, wait for pending operations before
* calling bdrv_get_dirty_count(bs), or we may exit while the
* source has dirty data to copy!
*
* Note that I/O can be submitted by the guest while
* mirror_populate runs.
*/
trace_mirror_before_drain(s, cnt);
bdrv_drain(bs);
cnt = bdrv_get_dirty_count(s->dirty_bitmap);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
ret = 0;
trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
if (!s->synced) {
block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
if (block_job_is_cancelled(&s->common)) {
break;
}
} else if (!should_complete) {
delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
} else if (cnt == 0) {
/* The two disks are in sync. Exit and report successful
* completion.
*/
assert(QLIST_EMPTY(&bs->tracked_requests));
s->common.cancelled = false;
break;
}
last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
immediate_exit:
if (s->in_flight > 0) {
/* We get here only if something went wrong. Either the job failed,
* or it was cancelled prematurely so that we do not guarantee that
* the target is a copy of the source.
*/
assert(ret < 0 || (!s->synced && block_job_is_cancelled(&s->common)));
mirror_drain(s);
}
assert(s->in_flight == 0);
qemu_vfree(s->buf);
g_free(s->cow_bitmap);
g_free(s->in_flight_bitmap);
bdrv_release_dirty_bitmap(bs, s->dirty_bitmap);
if (s->target->blk) {
blk_iostatus_disable(s->target->blk);
}
data = g_malloc(sizeof(*data));
data->ret = ret;
block_job_defer_to_main_loop(&s->common, mirror_exit, data);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
}
static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
if (speed < 0) {
error_setg(errp, QERR_INVALID_PARAMETER, "speed");
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
return;
}
ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
}
static void mirror_iostatus_reset(BlockJob *job)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
if (s->target->blk) {
blk_iostatus_reset(s->target->blk);
}
}
static void mirror_complete(BlockJob *job, Error **errp)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
Error *local_err = NULL;
int ret;
ret = bdrv_open_backing_file(s->target, NULL, &local_err);
if (ret < 0) {
error_propagate(errp, local_err);
return;
}
if (!s->synced) {
error_setg(errp, QERR_BLOCK_JOB_NOT_READY, job->id);
return;
}
/* check the target bs is not blocked and block all operations on it */
if (s->replaces) {
AioContext *replace_aio_context;
s->to_replace = bdrv_find_node(s->replaces);
if (!s->to_replace) {
error_setg(errp, "Node name '%s' not found", s->replaces);
return;
}
replace_aio_context = bdrv_get_aio_context(s->to_replace);
aio_context_acquire(replace_aio_context);
error_setg(&s->replace_blocker,
"block device is in use by block-job-complete");
bdrv_op_block_all(s->to_replace, s->replace_blocker);
bdrv_ref(s->to_replace);
aio_context_release(replace_aio_context);
}
s->should_complete = true;
block_job_enter(&s->common);
}
static const BlockJobDriver mirror_job_driver = {
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
.instance_size = sizeof(MirrorBlockJob),
.job_type = BLOCK_JOB_TYPE_MIRROR,
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
.set_speed = mirror_set_speed,
.iostatus_reset= mirror_iostatus_reset,
.complete = mirror_complete,
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
};
static const BlockJobDriver commit_active_job_driver = {
.instance_size = sizeof(MirrorBlockJob),
.job_type = BLOCK_JOB_TYPE_COMMIT,
.set_speed = mirror_set_speed,
.iostatus_reset
= mirror_iostatus_reset,
.complete = mirror_complete,
};
static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
const char *replaces,
int64_t speed, uint32_t granularity,
int64_t buf_size,
BlockdevOnError on_source_error,
BlockdevOnError on_target_error,
bool unmap,
BlockCompletionFunc *cb,
void *opaque, Error **errp,
const BlockJobDriver *driver,
bool is_none_mode, BlockDriverState *base)
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
{
MirrorBlockJob *s;
if (granularity == 0) {
granularity = bdrv_get_default_bitmap_granularity(target);
}
assert ((granularity & (granularity - 1)) == 0);
if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
(!bs->blk || !blk_iostatus_is_enabled(bs->blk))) {
error_setg(errp, QERR_INVALID_PARAMETER, "on-source-error");
return;
}
if (buf_size < 0) {
error_setg(errp, "Invalid parameter 'buf-size'");
return;
}
if (buf_size == 0) {
buf_size = DEFAULT_MIRROR_BUF_SIZE;
}
s = block_job_create(driver, bs, speed, cb, opaque, errp);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
if (!s) {
return;
}
s->replaces = g_strdup(replaces);
s->on_source_error = on_source_error;
s->on_target_error = on_target_error;
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
s->target = target;
s->is_none_mode = is_none_mode;
s->base = base;
s->granularity = granularity;
s->buf_size = ROUND_UP(buf_size, granularity);
s->unmap = unmap;
s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
if (!s->dirty_bitmap) {
g_free(s->replaces);
block_job_release(bs);
return;
}
bdrv_op_block_all(s->target, s->common.blocker);
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
bdrv_set_enable_write_cache(s->target, true);
if (s->target->blk) {
blk_set_on_error(s->target->blk, on_target_error, on_target_error);
blk_iostatus_enable(s->target->blk);
}
mirror: introduce mirror job This patch adds the implementation of a new job that mirrors a disk to a new image while letting the guest continue using the old image. The target is treated as a "black box" and data is copied from the source to the target in the background. This can be used for several purposes, including storage migration, continuous replication, and observation of the guest I/O in an external program. It is also a first step in replacing the inefficient block migration code that is part of QEMU. The job is possibly never-ending, but it is logically structured into two phases: 1) copy all data as fast as possible until the target first gets in sync with the source; 2) keep target in sync and ensure that reopening to the target gets a correct (full) copy of the source data. The second phase is indicated by the progress in "info block-jobs" reporting the current offset to be equal to the length of the file. When the job is cancelled in the second phase, QEMU will run the job until the source is clean and quiescent, then it will report successful completion of the job. In other words, the BLOCK_JOB_CANCELLED event means that the target may _not_ be consistent with a past state of the source; the BLOCK_JOB_COMPLETED event means that the target is consistent with a past state of the source. (Note that it could already happen that management lost the race against QEMU and got a completion event instead of cancellation). It is not yet possible to complete the job and switch over to the target disk. The next patches will fix this and add many refinements to the basic idea introduced here. These include improved error management, some tunable knobs and performance optimizations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-10-18 16:49:23 +02:00
s->common.co = qemu_coroutine_create(mirror_run);
trace_mirror_start(bs, s, s->common.co, opaque);
qemu_coroutine_enter(s->common.co, s);
}
void mirror_start(BlockDriverState *bs, BlockDriverState *target,
const char *replaces,
int64_t speed, uint32_t granularity, int64_t buf_size,
MirrorSyncMode mode, BlockdevOnError on_source_error,
BlockdevOnError on_target_error,
bool unmap,
BlockCompletionFunc *cb,
void *opaque, Error **errp)
{
bool is_none_mode;
BlockDriverState *base;
if (mode == MIRROR_SYNC_MODE_INCREMENTAL) {
error_setg(errp, "Sync mode 'incremental' not supported");
return;
}
is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
base = mode == MIRROR_SYNC_MODE_TOP ? backing_bs(bs) : NULL;
mirror_start_job(bs, target, replaces,
speed, granularity, buf_size,
on_source_error, on_target_error, unmap, cb, opaque, errp,
&mirror_job_driver, is_none_mode, base);
}
void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
int64_t speed,
BlockdevOnError on_error,
BlockCompletionFunc *cb,
void *opaque, Error **errp)
{
int64_t length, base_length;
int orig_base_flags;
int ret;
Error *local_err = NULL;
orig_base_flags = bdrv_get_flags(base);
if (bdrv_reopen(base, bs->open_flags, errp)) {
return;
}
length = bdrv_getlength(bs);
if (length < 0) {
error_setg_errno(errp, -length,
"Unable to determine length of %s", bs->filename);
goto error_restore_flags;
}
base_length = bdrv_getlength(base);
if (base_length < 0) {
error_setg_errno(errp, -base_length,
"Unable to determine length of %s", base->filename);
goto error_restore_flags;
}
if (length > base_length) {
ret = bdrv_truncate(base, length);
if (ret < 0) {
error_setg_errno(errp, -ret,
"Top image %s is larger than base image %s, and "
"resize of base image failed",
bs->filename, base->filename);
goto error_restore_flags;
}
}
bdrv_ref(base);
mirror_start_job(bs, base, NULL, speed, 0, 0,
on_error, on_error, false, cb, opaque, &local_err,
&commit_active_job_driver, false, base);
if (local_err) {
error_propagate(errp, local_err);
goto error_restore_flags;
}
return;
error_restore_flags:
/* ignore error and errp for bdrv_reopen, because we want to propagate
* the original error */
bdrv_reopen(base, orig_base_flags, NULL);
return;
}