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d44dae1a7c
qemu-e2k/block/mirror.c
Vladimir Sementsov-Ogievskiy d44dae1a7c block/mirror: fix active mirror dead-lock in mirror_wait_on_conflicts 
It's possible that requests start to wait each other in
mirror_wait_on_conflicts(). To avoid it let's use same technique as in
block/io.c in bdrv_wait_serialising_requests_locked() /
bdrv_find_conflicting_request(): don't wait on intersecting request if
it is already waiting for some other request.

For details of the dead-lock look at testIntersectingActiveIO()
test-case which we actually fixing now.

Fixes: d06107ade0
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210702211636.228981-4-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2021-07-20 13:14:45 +02:00

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/*
* 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 "qemu/osdep.h"
#include "qemu/cutils.h"
#include "qemu/coroutine.h"
#include "qemu/range.h"
#include "trace.h"
#include "block/blockjob_int.h"
#include "block/block_int.h"
#include "sysemu/block-backend.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qemu/ratelimit.h"
#include "qemu/bitmap.h"
#define MAX_IN_FLIGHT 16
#define MAX_IO_BYTES (1 << 20) /* 1 Mb */
#define DEFAULT_MIRROR_BUF_SIZE (MAX_IN_FLIGHT * MAX_IO_BYTES)
/* 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;
typedef struct MirrorOp MirrorOp;
typedef struct MirrorBlockJob {
BlockJob common;
BlockBackend *target;
BlockDriverState *mirror_top_bs;
BlockDriverState *base;
BlockDriverState *base_overlay;
/* 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;
BlockMirrorBackingMode backing_mode;
/* Whether the target image requires explicit zero-initialization */
bool zero_target;
MirrorCopyMode copy_mode;
BlockdevOnError on_source_error, on_target_error;
bool synced;
/* Set when the target is synced (dirty bitmap is clean, nothing
* in flight) and the job is running in active mode */
bool actively_synced;
bool should_complete;
int64_t granularity;
size_t buf_size;
int64_t bdev_length;
unsigned long *cow_bitmap;
BdrvDirtyBitmap *dirty_bitmap;
BdrvDirtyBitmapIter *dbi;
uint8_t *buf;
QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
int buf_free_count;
uint64_t last_pause_ns;
unsigned long *in_flight_bitmap;
int in_flight;
int64_t bytes_in_flight;
QTAILQ_HEAD(, MirrorOp) ops_in_flight;
int ret;
bool unmap;
int target_cluster_size;
int max_iov;
bool initial_zeroing_ongoing;
int in_active_write_counter;
bool prepared;
bool in_drain;
} MirrorBlockJob;
typedef struct MirrorBDSOpaque {
MirrorBlockJob *job;
bool stop;
bool is_commit;
} MirrorBDSOpaque;
struct MirrorOp {
MirrorBlockJob *s;
QEMUIOVector qiov;
int64_t offset;
uint64_t bytes;
/* The pointee is set by mirror_co_read(), mirror_co_zero(), and
* mirror_co_discard() before yielding for the first time */
int64_t *bytes_handled;
bool is_pseudo_op;
bool is_active_write;
bool is_in_flight;
CoQueue waiting_requests;
Coroutine *co;
MirrorOp *waiting_for_op;
QTAILQ_ENTRY(MirrorOp) next;
};
typedef enum MirrorMethod {
MIRROR_METHOD_COPY,
MIRROR_METHOD_ZERO,
MIRROR_METHOD_DISCARD,
} MirrorMethod;
static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
int error)
{
s->synced = false;
s->actively_synced = false;
if (read) {
return block_job_error_action(&s->common, s->on_source_error,
true, error);
} else {
return block_job_error_action(&s->common, s->on_target_error,
false, error);
}
}
static void coroutine_fn mirror_wait_on_conflicts(MirrorOp *self,
MirrorBlockJob *s,
uint64_t offset,
uint64_t bytes)
{
uint64_t self_start_chunk = offset / s->granularity;
uint64_t self_end_chunk = DIV_ROUND_UP(offset + bytes, s->granularity);
uint64_t self_nb_chunks = self_end_chunk - self_start_chunk;
while (find_next_bit(s->in_flight_bitmap, self_end_chunk,
self_start_chunk) < self_end_chunk &&
s->ret >= 0)
{
MirrorOp *op;
QTAILQ_FOREACH(op, &s->ops_in_flight, next) {
uint64_t op_start_chunk = op->offset / s->granularity;
uint64_t op_nb_chunks = DIV_ROUND_UP(op->offset + op->bytes,
s->granularity) -
op_start_chunk;
if (op == self) {
continue;
}
if (ranges_overlap(self_start_chunk, self_nb_chunks,
op_start_chunk, op_nb_chunks))
{
/*
* If the operation is already (indirectly) waiting for us, or
* will wait for us as soon as it wakes up, then just go on
* (instead of producing a deadlock in the former case).
*/
if (op->waiting_for_op) {
continue;
}
self->waiting_for_op = op;
qemu_co_queue_wait(&op->waiting_requests, NULL);
self->waiting_for_op = NULL;
break;
}
}
}
}
static void coroutine_fn mirror_iteration_done(MirrorOp *op, int ret)
{
MirrorBlockJob *s = op->s;
struct iovec *iov;
int64_t chunk_num;
int i, nb_chunks;
trace_mirror_iteration_done(s, op->offset, op->bytes, ret);
s->in_flight--;
s->bytes_in_flight -= op->bytes;
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++;
}
chunk_num = op->offset / s->granularity;
nb_chunks = DIV_ROUND_UP(op->bytes, s->granularity);
bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
QTAILQ_REMOVE(&s->ops_in_flight, op, next);
if (ret >= 0) {
if (s->cow_bitmap) {
bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
}
if (!s->initial_zeroing_ongoing) {
job_progress_update(&s->common.job, op->bytes);
}
}
qemu_iovec_destroy(&op->qiov);
qemu_co_queue_restart_all(&op->waiting_requests);
g_free(op);
}
static void coroutine_fn mirror_write_complete(MirrorOp *op, int ret)
{
MirrorBlockJob *s = op->s;
if (ret < 0) {
BlockErrorAction action;
bdrv_set_dirty_bitmap(s->dirty_bitmap, op->offset, op->bytes);
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 coroutine_fn mirror_read_complete(MirrorOp *op, int ret)
{
MirrorBlockJob *s = op->s;
if (ret < 0) {
BlockErrorAction action;
bdrv_set_dirty_bitmap(s->dirty_bitmap, op->offset, op->bytes);
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;
}
ret = blk_co_pwritev(s->target, op->offset, op->qiov.size, &op->qiov, 0);
mirror_write_complete(op, ret);
}
/* Clip bytes relative to offset to not exceed end-of-file */
static inline int64_t mirror_clip_bytes(MirrorBlockJob *s,
int64_t offset,
int64_t bytes)
{
return MIN(bytes, s->bdev_length - offset);
}
/* Round offset and/or bytes to target cluster if COW is needed, and
* return the offset of the adjusted tail against original. */
static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
uint64_t *bytes)
{
bool need_cow;
int ret = 0;
int64_t align_offset = *offset;
int64_t align_bytes = *bytes;
int max_bytes = s->granularity * s->max_iov;
need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap);
need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity,
s->cow_bitmap);
if (need_cow) {
bdrv_round_to_clusters(blk_bs(s->target), *offset, *bytes,
&align_offset, &align_bytes);
}
if (align_bytes > max_bytes) {
align_bytes = max_bytes;
if (need_cow) {
align_bytes = QEMU_ALIGN_DOWN(align_bytes, s->target_cluster_size);
}
}
/* Clipping may result in align_bytes unaligned to chunk boundary, but
* that doesn't matter because it's already the end of source image. */
align_bytes = mirror_clip_bytes(s, align_offset, align_bytes);
ret = align_offset + align_bytes - (*offset + *bytes);
*offset = align_offset;
*bytes = align_bytes;
assert(ret >= 0);
return ret;
}
static inline void coroutine_fn
mirror_wait_for_any_operation(MirrorBlockJob *s, bool active)
{
MirrorOp *op;
QTAILQ_FOREACH(op, &s->ops_in_flight, next) {
/* Do not wait on pseudo ops, because it may in turn wait on
* some other operation to start, which may in fact be the
* caller of this function. Since there is only one pseudo op
* at any given time, we will always find some real operation
* to wait on. */
if (!op->is_pseudo_op && op->is_in_flight &&
op->is_active_write == active)
{
qemu_co_queue_wait(&op->waiting_requests, NULL);
return;
}
}
abort();
}
static inline void coroutine_fn
mirror_wait_for_free_in_flight_slot(MirrorBlockJob *s)
{
/* Only non-active operations use up in-flight slots */
mirror_wait_for_any_operation(s, false);
}
/* Perform a mirror copy operation.
*
* *op->bytes_handled is set to the number of bytes copied after and
* including offset, excluding any bytes copied prior to offset due
* to alignment. This will be op->bytes if no alignment is necessary,
* or (new_end - op->offset) if the tail is rounded up or down due to
* alignment or buffer limit.
*/
static void coroutine_fn mirror_co_read(void *opaque)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
int nb_chunks;
uint64_t ret;
uint64_t max_bytes;
max_bytes = s->granularity * s->max_iov;
/* We can only handle as much as buf_size at a time. */
op->bytes = MIN(s->buf_size, MIN(max_bytes, op->bytes));
assert(op->bytes);
assert(op->bytes < BDRV_REQUEST_MAX_BYTES);
*op->bytes_handled = op->bytes;
if (s->cow_bitmap) {
*op->bytes_handled += mirror_cow_align(s, &op->offset, &op->bytes);
}
/* Cannot exceed BDRV_REQUEST_MAX_BYTES + INT_MAX */
assert(*op->bytes_handled <= UINT_MAX);
assert(op->bytes <= s->buf_size);
/* The offset is granularity-aligned because:
* 1) Caller passes in aligned values;
* 2) mirror_cow_align is used only when target cluster is larger. */
assert(QEMU_IS_ALIGNED(op->offset, s->granularity));
/* The range is sector-aligned, since bdrv_getlength() rounds up. */
assert(QEMU_IS_ALIGNED(op->bytes, BDRV_SECTOR_SIZE));
nb_chunks = DIV_ROUND_UP(op->bytes, s->granularity);
while (s->buf_free_count < nb_chunks) {
trace_mirror_yield_in_flight(s, op->offset, s->in_flight);
mirror_wait_for_free_in_flight_slot(s);
}
/* Now make a QEMUIOVector taking enough granularity-sized chunks
* from s->buf_free.
*/
qemu_iovec_init(&op->qiov, nb_chunks);
while (nb_chunks-- > 0) {
MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
size_t remaining = op->bytes - op->qiov.size;
QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
s->buf_free_count--;
qemu_iovec_add(&op->qiov, buf, MIN(s->granularity, remaining));
}
/* Copy the dirty cluster. */
s->in_flight++;
s->bytes_in_flight += op->bytes;
op->is_in_flight = true;
trace_mirror_one_iteration(s, op->offset, op->bytes);
ret = bdrv_co_preadv(s->mirror_top_bs->backing, op->offset, op->bytes,
&op->qiov, 0);
mirror_read_complete(op, ret);
}
static void coroutine_fn mirror_co_zero(void *opaque)
{
MirrorOp *op = opaque;
int ret;
op->s->in_flight++;
op->s->bytes_in_flight += op->bytes;
*op->bytes_handled = op->bytes;
op->is_in_flight = true;
ret = blk_co_pwrite_zeroes(op->s->target, op->offset, op->bytes,
op->s->unmap ? BDRV_REQ_MAY_UNMAP : 0);
mirror_write_complete(op, ret);
}
static void coroutine_fn mirror_co_discard(void *opaque)
{
MirrorOp *op = opaque;
int ret;
op->s->in_flight++;
op->s->bytes_in_flight += op->bytes;
*op->bytes_handled = op->bytes;
op->is_in_flight = true;
ret = blk_co_pdiscard(op->s->target, op->offset, op->bytes);
mirror_write_complete(op, ret);
}
static unsigned mirror_perform(MirrorBlockJob *s, int64_t offset,
unsigned bytes, MirrorMethod mirror_method)
{
MirrorOp *op;
Coroutine *co;
int64_t bytes_handled = -1;
op = g_new(MirrorOp, 1);
*op = (MirrorOp){
.s = s,
.offset = offset,
.bytes = bytes,
.bytes_handled = &bytes_handled,
};
qemu_co_queue_init(&op->waiting_requests);
switch (mirror_method) {
case MIRROR_METHOD_COPY:
co = qemu_coroutine_create(mirror_co_read, op);
break;
case MIRROR_METHOD_ZERO:
co = qemu_coroutine_create(mirror_co_zero, op);
break;
case MIRROR_METHOD_DISCARD:
co = qemu_coroutine_create(mirror_co_discard, op);
break;
default:
abort();
}
op->co = co;
QTAILQ_INSERT_TAIL(&s->ops_in_flight, op, next);
qemu_coroutine_enter(co);
/* At this point, ownership of op has been moved to the coroutine
* and the object may already be freed */
/* Assert that this value has been set */
assert(bytes_handled >= 0);
/* Same assertion as in mirror_co_read() (and for mirror_co_read()
* and mirror_co_discard(), bytes_handled == op->bytes, which
* is the @bytes parameter given to this function) */
assert(bytes_handled <= UINT_MAX);
return bytes_handled;
}
static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
{
BlockDriverState *source = s->mirror_top_bs->backing->bs;
MirrorOp *pseudo_op;
int64_t offset;
uint64_t delay_ns = 0, ret = 0;
/* At least the first dirty chunk is mirrored in one iteration. */
int nb_chunks = 1;
bool write_zeroes_ok = bdrv_can_write_zeroes_with_unmap(blk_bs(s->target));
int max_io_bytes = MAX(s->buf_size / MAX_IN_FLIGHT, MAX_IO_BYTES);
bdrv_dirty_bitmap_lock(s->dirty_bitmap);
offset = bdrv_dirty_iter_next(s->dbi);
if (offset < 0) {
bdrv_set_dirty_iter(s->dbi, 0);
offset = bdrv_dirty_iter_next(s->dbi);
trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap));
assert(offset >= 0);
}
bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
mirror_wait_on_conflicts(NULL, s, offset, 1);
job_pause_point(&s->common.job);
/* Find the number of consective dirty chunks following the first dirty
* one, and wait for in flight requests in them. */
bdrv_dirty_bitmap_lock(s->dirty_bitmap);
while (nb_chunks * s->granularity < s->buf_size) {
int64_t next_dirty;
int64_t next_offset = offset + nb_chunks * s->granularity;
int64_t next_chunk = next_offset / s->granularity;
if (next_offset >= s->bdev_length ||
!bdrv_dirty_bitmap_get_locked(s->dirty_bitmap, next_offset)) {
break;
}
if (test_bit(next_chunk, s->in_flight_bitmap)) {
break;
}
next_dirty = bdrv_dirty_iter_next(s->dbi);
if (next_dirty > next_offset || next_dirty < 0) {
/* The bitmap iterator's cache is stale, refresh it */
bdrv_set_dirty_iter(s->dbi, next_offset);
next_dirty = bdrv_dirty_iter_next(s->dbi);
}
assert(next_dirty == next_offset);
nb_chunks++;
}
/* Clear dirty bits before querying the block status, because
* calling bdrv_block_status_above could yield - if some blocks are
* marked dirty in this window, we need to know.
*/
bdrv_reset_dirty_bitmap_locked(s->dirty_bitmap, offset,
nb_chunks * s->granularity);
bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
/* Before claiming an area in the in-flight bitmap, we have to
* create a MirrorOp for it so that conflicting requests can wait
* for it. mirror_perform() will create the real MirrorOps later,
* for now we just create a pseudo operation that will wake up all
* conflicting requests once all real operations have been
* launched. */
pseudo_op = g_new(MirrorOp, 1);
*pseudo_op = (MirrorOp){
.offset = offset,
.bytes = nb_chunks * s->granularity,
.is_pseudo_op = true,
};
qemu_co_queue_init(&pseudo_op->waiting_requests);
QTAILQ_INSERT_TAIL(&s->ops_in_flight, pseudo_op, next);
bitmap_set(s->in_flight_bitmap, offset / s->granularity, nb_chunks);
while (nb_chunks > 0 && offset < s->bdev_length) {
int ret;
int64_t io_bytes;
int64_t io_bytes_acct;
MirrorMethod mirror_method = MIRROR_METHOD_COPY;
assert(!(offset % s->granularity));
ret = bdrv_block_status_above(source, NULL, offset,
nb_chunks * s->granularity,
&io_bytes, NULL, NULL);
if (ret < 0) {
io_bytes = MIN(nb_chunks * s->granularity, max_io_bytes);
} else if (ret & BDRV_BLOCK_DATA) {
io_bytes = MIN(io_bytes, max_io_bytes);
}
io_bytes -= io_bytes % s->granularity;
if (io_bytes < s->granularity) {
io_bytes = s->granularity;
} else if (ret >= 0 && !(ret & BDRV_BLOCK_DATA)) {
int64_t target_offset;
int64_t target_bytes;
bdrv_round_to_clusters(blk_bs(s->target), offset, io_bytes,
&target_offset, &target_bytes);
if (target_offset == offset &&
target_bytes == io_bytes) {
mirror_method = ret & BDRV_BLOCK_ZERO ?
MIRROR_METHOD_ZERO :
MIRROR_METHOD_DISCARD;
}
}
while (s->in_flight >= MAX_IN_FLIGHT) {
trace_mirror_yield_in_flight(s, offset, s->in_flight);
mirror_wait_for_free_in_flight_slot(s);
}
if (s->ret < 0) {
ret = 0;
goto fail;
}
io_bytes = mirror_clip_bytes(s, offset, io_bytes);
io_bytes = mirror_perform(s, offset, io_bytes, mirror_method);
if (mirror_method != MIRROR_METHOD_COPY && write_zeroes_ok) {
io_bytes_acct = 0;
} else {
io_bytes_acct = io_bytes;
}
assert(io_bytes);
offset += io_bytes;
nb_chunks -= DIV_ROUND_UP(io_bytes, s->granularity);
delay_ns = block_job_ratelimit_get_delay(&s->common, io_bytes_acct);
}
ret = delay_ns;
fail:
QTAILQ_REMOVE(&s->ops_in_flight, pseudo_op, next);
qemu_co_queue_restart_all(&pseudo_op->waiting_requests);
g_free(pseudo_op);
return ret;
}
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;
}
}
/* This is also used for the .pause callback. There is no matching
* mirror_resume() because mirror_run() will begin iterating again
* when the job is resumed.
*/
static void coroutine_fn mirror_wait_for_all_io(MirrorBlockJob *s)
{
while (s->in_flight > 0) {
mirror_wait_for_free_in_flight_slot(s);
}
}
/**
* mirror_exit_common: handle both abort() and prepare() cases.
* for .prepare, returns 0 on success and -errno on failure.
* for .abort cases, denoted by abort = true, MUST return 0.
*/
static int mirror_exit_common(Job *job)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
BlockJob *bjob = &s->common;
MirrorBDSOpaque *bs_opaque;
AioContext *replace_aio_context = NULL;
BlockDriverState *src;
BlockDriverState *target_bs;
BlockDriverState *mirror_top_bs;
Error *local_err = NULL;
bool abort = job->ret < 0;
int ret = 0;
if (s->prepared) {
return 0;
}
s->prepared = true;
mirror_top_bs = s->mirror_top_bs;
bs_opaque = mirror_top_bs->opaque;
src = mirror_top_bs->backing->bs;
target_bs = blk_bs(s->target);
if (bdrv_chain_contains(src, target_bs)) {
bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs);
}
bdrv_release_dirty_bitmap(s->dirty_bitmap);
/* Make sure that the source BDS doesn't go away during bdrv_replace_node,
* before we can call bdrv_drained_end */
bdrv_ref(src);
bdrv_ref(mirror_top_bs);
bdrv_ref(target_bs);
/*
* Remove target parent that still uses BLK_PERM_WRITE/RESIZE before
* inserting target_bs at s->to_replace, where we might not be able to get
* these permissions.
*/
blk_unref(s->target);
s->target = NULL;
/* We don't access the source any more. Dropping any WRITE/RESIZE is
* required before it could become a backing file of target_bs. Not having
* these permissions any more means that we can't allow any new requests on
* mirror_top_bs from now on, so keep it drained. */
bdrv_drained_begin(mirror_top_bs);
bs_opaque->stop = true;
bdrv_child_refresh_perms(mirror_top_bs, mirror_top_bs->backing,
&error_abort);
if (!abort && s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) {
BlockDriverState *backing = s->is_none_mode ? src : s->base;
BlockDriverState *unfiltered_target = bdrv_skip_filters(target_bs);
if (bdrv_cow_bs(unfiltered_target) != backing) {
bdrv_set_backing_hd(unfiltered_target, backing, &local_err);
if (local_err) {
error_report_err(local_err);
local_err = NULL;
ret = -EPERM;
}
}
} else if (!abort && s->backing_mode == MIRROR_OPEN_BACKING_CHAIN) {
assert(!bdrv_backing_chain_next(target_bs));
ret = bdrv_open_backing_file(bdrv_skip_filters(target_bs), NULL,
"backing", &local_err);
if (ret < 0) {
error_report_err(local_err);
local_err = NULL;
}
}
if (s->to_replace) {
replace_aio_context = bdrv_get_aio_context(s->to_replace);
aio_context_acquire(replace_aio_context);
}
if (s->should_complete && !abort) {
BlockDriverState *to_replace = s->to_replace ?: src;
bool ro = bdrv_is_read_only(to_replace);
if (ro != bdrv_is_read_only(target_bs)) {
bdrv_reopen_set_read_only(target_bs, ro, NULL);
}
/* The mirror job has no requests in flight any more, but we need to
* drain potential other users of the BDS before changing the graph. */
assert(s->in_drain);
bdrv_drained_begin(target_bs);
/*
* Cannot use check_to_replace_node() here, because that would
* check for an op blocker on @to_replace, and we have our own
* there.
*/
if (bdrv_recurse_can_replace(src, to_replace)) {
bdrv_replace_node(to_replace, target_bs, &local_err);
} else {
error_setg(&local_err, "Can no longer replace '%s' by '%s', "
"because it can no longer be guaranteed that doing so "
"would not lead to an abrupt change of visible data",
to_replace->node_name, target_bs->node_name);
}
bdrv_drained_end(target_bs);
if (local_err) {
error_report_err(local_err);
ret = -EPERM;
}
}
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_unref(target_bs);
/*
* Remove the mirror filter driver from the graph. Before this, get rid of
* the blockers on the intermediate nodes so that the resulting state is
* valid.
*/
block_job_remove_all_bdrv(bjob);
bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, &error_abort);
/* We just changed the BDS the job BB refers to (with either or both of the
* bdrv_replace_node() calls), so switch the BB back so the cleanup does
* the right thing. We don't need any permissions any more now. */
blk_remove_bs(bjob->blk);
blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
blk_insert_bs(bjob->blk, mirror_top_bs, &error_abort);
bs_opaque->job = NULL;
bdrv_drained_end(src);
bdrv_drained_end(mirror_top_bs);
s->in_drain = false;
bdrv_unref(mirror_top_bs);
bdrv_unref(src);
return ret;
}
static int mirror_prepare(Job *job)
{
return mirror_exit_common(job);
}
static void mirror_abort(Job *job)
{
int ret = mirror_exit_common(job);
assert(ret == 0);
}
static void coroutine_fn mirror_throttle(MirrorBlockJob *s)
{
int64_t now = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
if (now - s->last_pause_ns > BLOCK_JOB_SLICE_TIME) {
s->last_pause_ns = now;
job_sleep_ns(&s->common.job, 0);
} else {
job_pause_point(&s->common.job);
}
}
static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
{
int64_t offset;
BlockDriverState *bs = s->mirror_top_bs->backing->bs;
BlockDriverState *target_bs = blk_bs(s->target);
int ret;
int64_t count;
if (s->zero_target) {
if (!bdrv_can_write_zeroes_with_unmap(target_bs)) {
bdrv_set_dirty_bitmap(s->dirty_bitmap, 0, s->bdev_length);
return 0;
}
s->initial_zeroing_ongoing = true;
for (offset = 0; offset < s->bdev_length; ) {
int bytes = MIN(s->bdev_length - offset,
QEMU_ALIGN_DOWN(INT_MAX, s->granularity));
mirror_throttle(s);
if (job_is_cancelled(&s->common.job)) {
s->initial_zeroing_ongoing = false;
return 0;
}
if (s->in_flight >= MAX_IN_FLIGHT) {
trace_mirror_yield(s, UINT64_MAX, s->buf_free_count,
s->in_flight);
mirror_wait_for_free_in_flight_slot(s);
continue;
}
mirror_perform(s, offset, bytes, MIRROR_METHOD_ZERO);
offset += bytes;
}
mirror_wait_for_all_io(s);
s->initial_zeroing_ongoing = false;
}
/* First part, loop on the sectors and initialize the dirty bitmap. */
for (offset = 0; offset < s->bdev_length; ) {
/* Just to make sure we are not exceeding int limit. */
int bytes = MIN(s->bdev_length - offset,
QEMU_ALIGN_DOWN(INT_MAX, s->granularity));
mirror_throttle(s);
if (job_is_cancelled(&s->common.job)) {
return 0;
}
ret = bdrv_is_allocated_above(bs, s->base_overlay, true, offset, bytes,
&count);
if (ret < 0) {
return ret;
}
assert(count);
if (ret > 0) {
bdrv_set_dirty_bitmap(s->dirty_bitmap, offset, count);
}
offset += count;
}
return 0;
}
/* Called when going out of the streaming phase to flush the bulk of the
* data to the medium, or just before completing.
*/
static int mirror_flush(MirrorBlockJob *s)
{
int ret = blk_flush(s->target);
if (ret < 0) {
if (mirror_error_action(s, false, -ret) == BLOCK_ERROR_ACTION_REPORT) {
s->ret = ret;
}
}
return ret;
}
static int coroutine_fn mirror_run(Job *job, Error **errp)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
BlockDriverState *bs = s->mirror_top_bs->backing->bs;
BlockDriverState *target_bs = blk_bs(s->target);
bool need_drain = true;
int64_t length;
int64_t target_length;
BlockDriverInfo bdi;
char backing_filename[2]; /* we only need 2 characters because we are only
checking for a NULL string */
int ret = 0;
if (job_is_cancelled(&s->common.job)) {
goto immediate_exit;
}
s->bdev_length = bdrv_getlength(bs);
if (s->bdev_length < 0) {
ret = s->bdev_length;
goto immediate_exit;
}
target_length = blk_getlength(s->target);
if (target_length < 0) {
ret = target_length;
goto immediate_exit;
}
/* Active commit must resize the base image if its size differs from the
* active layer. */
if (s->base == blk_bs(s->target)) {
if (s->bdev_length > target_length) {
ret = blk_truncate(s->target, s->bdev_length, false,
PREALLOC_MODE_OFF, 0, NULL);
if (ret < 0) {
goto immediate_exit;
}
}
} else if (s->bdev_length != target_length) {
error_setg(errp, "Source and target image have different sizes");
ret = -EINVAL;
goto immediate_exit;
}
if (s->bdev_length == 0) {
/* Transition to the READY state and wait for complete. */
job_transition_to_ready(&s->common.job);
s->synced = true;
s->actively_synced = true;
while (!job_is_cancelled(&s->common.job) && !s->should_complete) {
job_yield(&s->common.job);
}
s->common.job.cancelled = false;
goto immediate_exit;
}
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(target_bs, backing_filename,
sizeof(backing_filename));
if (!bdrv_get_info(target_bs, &bdi) && bdi.cluster_size) {
s->target_cluster_size = bdi.cluster_size;
} else {
s->target_cluster_size = BDRV_SECTOR_SIZE;
}
if (backing_filename[0] && !bdrv_backing_chain_next(target_bs) &&
s->granularity < s->target_cluster_size) {
s->buf_size = MAX(s->buf_size, s->target_cluster_size);
s->cow_bitmap = bitmap_new(length);
}
s->max_iov = MIN(bs->bl.max_iov, target_bs->bl.max_iov);
s->buf = qemu_try_blockalign(bs, s->buf_size);
if (s->buf == NULL) {
ret = -ENOMEM;
goto immediate_exit;
}
mirror_free_init(s);
s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
if (!s->is_none_mode) {
ret = mirror_dirty_init(s);
if (ret < 0 || job_is_cancelled(&s->common.job)) {
goto immediate_exit;
}
}
assert(!s->dbi);
s->dbi = bdrv_dirty_iter_new(s->dirty_bitmap);
for (;;) {
uint64_t delay_ns = 0;
int64_t cnt, delta;
bool should_complete;
/* Do not start passive operations while there are active
* writes in progress */
while (s->in_active_write_counter) {
mirror_wait_for_any_operation(s, true);
}
if (s->ret < 0) {
ret = s->ret;
goto immediate_exit;
}
job_pause_point(&s->common.job);
cnt = bdrv_get_dirty_count(s->dirty_bitmap);
/* cnt is the number of dirty bytes remaining and s->bytes_in_flight is
* the number of bytes currently being processed; together those are
* the current remaining operation length */
job_progress_set_remaining(&s->common.job, s->bytes_in_flight + cnt);
/* 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 BLKOCK_JOB_SLICE_TIME nanoseconds, or when there is
* an error, or when the source is clean, whichever comes first. */
delta = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - s->last_pause_ns;
if (delta < BLOCK_JOB_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, cnt, s->buf_free_count, s->in_flight);
mirror_wait_for_free_in_flight_slot(s);
continue;
} else if (cnt != 0) {
delay_ns = mirror_iteration(s);
}
}
should_complete = false;
if (s->in_flight == 0 && cnt == 0) {
trace_mirror_before_flush(s);
if (!s->synced) {
if (mirror_flush(s) < 0) {
/* Go check s->ret. */
continue;
}
/* 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.
*/
job_transition_to_ready(&s->common.job);
s->synced = true;
if (s->copy_mode != MIRROR_COPY_MODE_BACKGROUND) {
s->actively_synced = true;
}
}
should_complete = s->should_complete ||
job_is_cancelled(&s->common.job);
cnt = bdrv_get_dirty_count(s->dirty_bitmap);
}
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, so pause it now. Before deciding
* whether to switch to target check one last time if I/O has
* come in the meanwhile, and if not flush the data to disk.
*/
trace_mirror_before_drain(s, cnt);
s->in_drain = true;
bdrv_drained_begin(bs);
cnt = bdrv_get_dirty_count(s->dirty_bitmap);
if (cnt > 0 || mirror_flush(s) < 0) {
bdrv_drained_end(bs);
s->in_drain = false;
continue;
}
/* The two disks are in sync. Exit and report successful
* completion.
*/
assert(QLIST_EMPTY(&bs->tracked_requests));
s->common.job.cancelled = false;
need_drain = false;
break;
}
ret = 0;
if (s->synced && !should_complete) {
delay_ns = (s->in_flight == 0 &&
cnt == 0 ? BLOCK_JOB_SLICE_TIME : 0);
}
trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
job_sleep_ns(&s->common.job, delay_ns);
if (job_is_cancelled(&s->common.job) &&
(!s->synced || s->common.job.force_cancel))
{
break;
}
s->last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
}
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->common.job.force_cancel || !s->synced) &&
job_is_cancelled(&s->common.job)));
assert(need_drain);
mirror_wait_for_all_io(s);
}
assert(s->in_flight == 0);
qemu_vfree(s->buf);
g_free(s->cow_bitmap);
g_free(s->in_flight_bitmap);
bdrv_dirty_iter_free(s->dbi);
if (need_drain) {
s->in_drain = true;
bdrv_drained_begin(bs);
}
return ret;
}
static void mirror_complete(Job *job, Error **errp)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
if (!s->synced) {
error_setg(errp, "The active block job '%s' cannot be completed",
job->id);
return;
}
/* block all operations on to_replace bs */
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);
/* TODO Translate this into permission system. Current definition of
* GRAPH_MOD would require to request it for the parents; they might
* not even be BlockDriverStates, however, so a BdrvChild can't address
* them. May need redefinition of GRAPH_MOD. */
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;
/* If the job is paused, it will be re-entered when it is resumed */
if (!job->paused) {
job_enter(job);
}
}
static void coroutine_fn mirror_pause(Job *job)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
mirror_wait_for_all_io(s);
}
static bool mirror_drained_poll(BlockJob *job)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
/* If the job isn't paused nor cancelled, we can't be sure that it won't
* issue more requests. We make an exception if we've reached this point
* from one of our own drain sections, to avoid a deadlock waiting for
* ourselves.
*/
if (!s->common.job.paused && !s->common.job.cancelled && !s->in_drain) {
return true;
}
return !!s->in_flight;
}
static void mirror_cancel(Job *job, bool force)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
BlockDriverState *target = blk_bs(s->target);
if (force || !job_is_ready(job)) {
bdrv_cancel_in_flight(target);
}
}
static const BlockJobDriver mirror_job_driver = {
.job_driver = {
.instance_size = sizeof(MirrorBlockJob),
.job_type = JOB_TYPE_MIRROR,
.free = block_job_free,
.user_resume = block_job_user_resume,
.run = mirror_run,
.prepare = mirror_prepare,
.abort = mirror_abort,
.pause = mirror_pause,
.complete = mirror_complete,
.cancel = mirror_cancel,
},
.drained_poll = mirror_drained_poll,
};
static const BlockJobDriver commit_active_job_driver = {
.job_driver = {
.instance_size = sizeof(MirrorBlockJob),
.job_type = JOB_TYPE_COMMIT,
.free = block_job_free,
.user_resume = block_job_user_resume,
.run = mirror_run,
.prepare = mirror_prepare,
.abort = mirror_abort,
.pause = mirror_pause,
.complete = mirror_complete,
},
.drained_poll = mirror_drained_poll,
};
static void coroutine_fn
do_sync_target_write(MirrorBlockJob *job, MirrorMethod method,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
int ret;
size_t qiov_offset = 0;
int64_t bitmap_offset, bitmap_end;
if (!QEMU_IS_ALIGNED(offset, job->granularity) &&
bdrv_dirty_bitmap_get(job->dirty_bitmap, offset))
{
/*
* Dirty unaligned padding: ignore it.
*
* Reasoning:
* 1. If we copy it, we can't reset corresponding bit in
* dirty_bitmap as there may be some "dirty" bytes still not
* copied.
* 2. It's already dirty, so skipping it we don't diverge mirror
* progress.
*
* Note, that because of this, guest write may have no contribution
* into mirror converge, but that's not bad, as we have background
* process of mirroring. If under some bad circumstances (high guest
* IO load) background process starve, we will not converge anyway,
* even if each write will contribute, as guest is not guaranteed to
* rewrite the whole disk.
*/
qiov_offset = QEMU_ALIGN_UP(offset, job->granularity) - offset;
if (bytes <= qiov_offset) {
/* nothing to do after shrink */
return;
}
offset += qiov_offset;
bytes -= qiov_offset;
}
if (!QEMU_IS_ALIGNED(offset + bytes, job->granularity) &&
bdrv_dirty_bitmap_get(job->dirty_bitmap, offset + bytes - 1))
{
uint64_t tail = (offset + bytes) % job->granularity;
if (bytes <= tail) {
/* nothing to do after shrink */
return;
}
bytes -= tail;
}
/*
* Tails are either clean or shrunk, so for bitmap resetting
* we safely align the range down.
*/
bitmap_offset = QEMU_ALIGN_UP(offset, job->granularity);
bitmap_end = QEMU_ALIGN_DOWN(offset + bytes, job->granularity);
if (bitmap_offset < bitmap_end) {
bdrv_reset_dirty_bitmap(job->dirty_bitmap, bitmap_offset,
bitmap_end - bitmap_offset);
}
job_progress_increase_remaining(&job->common.job, bytes);
switch (method) {
case MIRROR_METHOD_COPY:
ret = blk_co_pwritev_part(job->target, offset, bytes,
qiov, qiov_offset, flags);
break;
case MIRROR_METHOD_ZERO:
assert(!qiov);
ret = blk_co_pwrite_zeroes(job->target, offset, bytes, flags);
break;
case MIRROR_METHOD_DISCARD:
assert(!qiov);
ret = blk_co_pdiscard(job->target, offset, bytes);
break;
default:
abort();
}
if (ret >= 0) {
job_progress_update(&job->common.job, bytes);
} else {
BlockErrorAction action;
/*
* We failed, so we should mark dirty the whole area, aligned up.
* Note that we don't care about shrunk tails if any: they were dirty
* at function start, and they must be still dirty, as we've locked
* the region for in-flight op.
*/
bitmap_offset = QEMU_ALIGN_DOWN(offset, job->granularity);
bitmap_end = QEMU_ALIGN_UP(offset + bytes, job->granularity);
bdrv_set_dirty_bitmap(job->dirty_bitmap, bitmap_offset,
bitmap_end - bitmap_offset);
job->actively_synced = false;
action = mirror_error_action(job, false, -ret);
if (action == BLOCK_ERROR_ACTION_REPORT) {
if (!job->ret) {
job->ret = ret;
}
}
}
}
static MirrorOp *coroutine_fn active_write_prepare(MirrorBlockJob *s,
uint64_t offset,
uint64_t bytes)
{
MirrorOp *op;
uint64_t start_chunk = offset / s->granularity;
uint64_t end_chunk = DIV_ROUND_UP(offset + bytes, s->granularity);
op = g_new(MirrorOp, 1);
*op = (MirrorOp){
.s = s,
.offset = offset,
.bytes = bytes,
.is_active_write = true,
.is_in_flight = true,
.co = qemu_coroutine_self(),
};
qemu_co_queue_init(&op->waiting_requests);
QTAILQ_INSERT_TAIL(&s->ops_in_flight, op, next);
s->in_active_write_counter++;
mirror_wait_on_conflicts(op, s, offset, bytes);
bitmap_set(s->in_flight_bitmap, start_chunk, end_chunk - start_chunk);
return op;
}
static void coroutine_fn active_write_settle(MirrorOp *op)
{
uint64_t start_chunk = op->offset / op->s->granularity;
uint64_t end_chunk = DIV_ROUND_UP(op->offset + op->bytes,
op->s->granularity);
if (!--op->s->in_active_write_counter && op->s->actively_synced) {
BdrvChild *source = op->s->mirror_top_bs->backing;
if (QLIST_FIRST(&source->bs->parents) == source &&
QLIST_NEXT(source, next_parent) == NULL)
{
/* Assert that we are back in sync once all active write
* operations are settled.
* Note that we can only assert this if the mirror node
* is the source node's only parent. */
assert(!bdrv_get_dirty_count(op->s->dirty_bitmap));
}
}
bitmap_clear(op->s->in_flight_bitmap, start_chunk, end_chunk - start_chunk);
QTAILQ_REMOVE(&op->s->ops_in_flight, op, next);
qemu_co_queue_restart_all(&op->waiting_requests);
g_free(op);
}
static int coroutine_fn bdrv_mirror_top_preadv(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
{
return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
}
static int coroutine_fn bdrv_mirror_top_do_write(BlockDriverState *bs,
MirrorMethod method, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov,
int flags)
{
MirrorOp *op = NULL;
MirrorBDSOpaque *s = bs->opaque;
int ret = 0;
bool copy_to_target;
copy_to_target = s->job->ret >= 0 &&
s->job->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING;
if (copy_to_target) {
op = active_write_prepare(s->job, offset, bytes);
}
switch (method) {
case MIRROR_METHOD_COPY:
ret = bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
break;
case MIRROR_METHOD_ZERO:
ret = bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags);
break;
case MIRROR_METHOD_DISCARD:
ret = bdrv_co_pdiscard(bs->backing, offset, bytes);
break;
default:
abort();
}
if (ret < 0) {
goto out;
}
if (copy_to_target) {
do_sync_target_write(s->job, method, offset, bytes, qiov, flags);
}
out:
if (copy_to_target) {
active_write_settle(op);
}
return ret;
}
static int coroutine_fn bdrv_mirror_top_pwritev(BlockDriverState *bs,
uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
{
MirrorBDSOpaque *s = bs->opaque;
QEMUIOVector bounce_qiov;
void *bounce_buf;
int ret = 0;
bool copy_to_target;
copy_to_target = s->job->ret >= 0 &&
s->job->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING;
if (copy_to_target) {
/* The guest might concurrently modify the data to write; but
* the data on source and destination must match, so we have
* to use a bounce buffer if we are going to write to the
* target now. */
bounce_buf = qemu_blockalign(bs, bytes);
iov_to_buf_full(qiov->iov, qiov->niov, 0, bounce_buf, bytes);
qemu_iovec_init(&bounce_qiov, 1);
qemu_iovec_add(&bounce_qiov, bounce_buf, bytes);
qiov = &bounce_qiov;
}
ret = bdrv_mirror_top_do_write(bs, MIRROR_METHOD_COPY, offset, bytes, qiov,
flags);
if (copy_to_target) {
qemu_iovec_destroy(&bounce_qiov);
qemu_vfree(bounce_buf);
}
return ret;
}
static int coroutine_fn bdrv_mirror_top_flush(BlockDriverState *bs)
{
if (bs->backing == NULL) {
/* we can be here after failed bdrv_append in mirror_start_job */
return 0;
}
return bdrv_co_flush(bs->backing->bs);
}
static int coroutine_fn bdrv_mirror_top_pwrite_zeroes(BlockDriverState *bs,
int64_t offset, int bytes, BdrvRequestFlags flags)
{
return bdrv_mirror_top_do_write(bs, MIRROR_METHOD_ZERO, offset, bytes, NULL,
flags);
}
static int coroutine_fn bdrv_mirror_top_pdiscard(BlockDriverState *bs,
int64_t offset, int bytes)
{
return bdrv_mirror_top_do_write(bs, MIRROR_METHOD_DISCARD, offset, bytes,
NULL, 0);
}
static void bdrv_mirror_top_refresh_filename(BlockDriverState *bs)
{
if (bs->backing == NULL) {
/* we can be here after failed bdrv_attach_child in
* bdrv_set_backing_hd */
return;
}
pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
bs->backing->bs->filename);
}
static void bdrv_mirror_top_child_perm(BlockDriverState *bs, BdrvChild *c,
BdrvChildRole role,
BlockReopenQueue *reopen_queue,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
MirrorBDSOpaque *s = bs->opaque;
if (s->stop) {
/*
* If the job is to be stopped, we do not need to forward
* anything to the real image.
*/
*nperm = 0;
*nshared = BLK_PERM_ALL;
return;
}
bdrv_default_perms(bs, c, role, reopen_queue,
perm, shared, nperm, nshared);
if (s->is_commit) {
/*
* For commit jobs, we cannot take CONSISTENT_READ, because
* that permission is unshared for everything above the base
* node (except for filters on the base node).
* We also have to force-share the WRITE permission, or
* otherwise we would block ourselves at the base node (if
* writes are blocked for a node, they are also blocked for
* its backing file).
* (We could also share RESIZE, because it may be needed for
* the target if its size is less than the top node's; but
* bdrv_default_perms_for_cow() automatically shares RESIZE
* for backing nodes if WRITE is shared, so there is no need
* to do it here.)
*/
*nperm &= ~BLK_PERM_CONSISTENT_READ;
*nshared |= BLK_PERM_WRITE;
}
}
/* Dummy node that provides consistent read to its users without requiring it
* from its backing file and that allows writes on the backing file chain. */
static BlockDriver bdrv_mirror_top = {
.format_name = "mirror_top",
.bdrv_co_preadv = bdrv_mirror_top_preadv,
.bdrv_co_pwritev = bdrv_mirror_top_pwritev,
.bdrv_co_pwrite_zeroes = bdrv_mirror_top_pwrite_zeroes,
.bdrv_co_pdiscard = bdrv_mirror_top_pdiscard,
.bdrv_co_flush = bdrv_mirror_top_flush,
.bdrv_refresh_filename = bdrv_mirror_top_refresh_filename,
.bdrv_child_perm = bdrv_mirror_top_child_perm,
.is_filter = true,
};
static BlockJob *mirror_start_job(
const char *job_id, BlockDriverState *bs,
int creation_flags, BlockDriverState *target,
const char *replaces, int64_t speed,
uint32_t granularity, int64_t buf_size,
BlockMirrorBackingMode backing_mode,
bool zero_target,
BlockdevOnError on_source_error,
BlockdevOnError on_target_error,
bool unmap,
BlockCompletionFunc *cb,
void *opaque,
const BlockJobDriver *driver,
bool is_none_mode, BlockDriverState *base,
bool auto_complete, const char *filter_node_name,
bool is_mirror, MirrorCopyMode copy_mode,
Error **errp)
{
MirrorBlockJob *s;
MirrorBDSOpaque *bs_opaque;
BlockDriverState *mirror_top_bs;
bool target_is_backing;
uint64_t target_perms, target_shared_perms;
int ret;
if (granularity == 0) {
granularity = bdrv_get_default_bitmap_granularity(target);
}
assert(is_power_of_2(granularity));
if (buf_size < 0) {
error_setg(errp, "Invalid parameter 'buf-size'");
return NULL;
}
if (buf_size == 0) {
buf_size = DEFAULT_MIRROR_BUF_SIZE;
}
if (bdrv_skip_filters(bs) == bdrv_skip_filters(target)) {
error_setg(errp, "Can't mirror node into itself");
return NULL;
}
target_is_backing = bdrv_chain_contains(bs, target);
/* In the case of active commit, add dummy driver to provide consistent
* reads on the top, while disabling it in the intermediate nodes, and make
* the backing chain writable. */
mirror_top_bs = bdrv_new_open_driver(&bdrv_mirror_top, filter_node_name,
BDRV_O_RDWR, errp);
if (mirror_top_bs == NULL) {
return NULL;
}
if (!filter_node_name) {
mirror_top_bs->implicit = true;
}
/* So that we can always drop this node */
mirror_top_bs->never_freeze = true;
mirror_top_bs->total_sectors = bs->total_sectors;
mirror_top_bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED;
mirror_top_bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
BDRV_REQ_NO_FALLBACK;
bs_opaque = g_new0(MirrorBDSOpaque, 1);
mirror_top_bs->opaque = bs_opaque;
bs_opaque->is_commit = target_is_backing;
bdrv_drained_begin(bs);
ret = bdrv_append(mirror_top_bs, bs, errp);
bdrv_drained_end(bs);
if (ret < 0) {
bdrv_unref(mirror_top_bs);
return NULL;
}
/* Make sure that the source is not resized while the job is running */
s = block_job_create(job_id, driver, NULL, mirror_top_bs,
BLK_PERM_CONSISTENT_READ,
BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
BLK_PERM_WRITE | BLK_PERM_GRAPH_MOD, speed,
creation_flags, cb, opaque, errp);
if (!s) {
goto fail;
}
bs_opaque->job = s;
/* The block job now has a reference to this node */
bdrv_unref(mirror_top_bs);
s->mirror_top_bs = mirror_top_bs;
/* No resize for the target either; while the mirror is still running, a
* consistent read isn't necessarily possible. We could possibly allow
* writes and graph modifications, though it would likely defeat the
* purpose of a mirror, so leave them blocked for now.
*
* In the case of active commit, things look a bit different, though,
* because the target is an already populated backing file in active use.
* We can allow anything except resize there.*/
target_perms = BLK_PERM_WRITE;
target_shared_perms = BLK_PERM_WRITE_UNCHANGED;
if (target_is_backing) {
int64_t bs_size, target_size;
bs_size = bdrv_getlength(bs);
if (bs_size < 0) {
error_setg_errno(errp, -bs_size,
"Could not inquire top image size");
goto fail;
}
target_size = bdrv_getlength(target);
if (target_size < 0) {
error_setg_errno(errp, -target_size,
"Could not inquire base image size");
goto fail;
}
if (target_size < bs_size) {
target_perms |= BLK_PERM_RESIZE;
}
target_shared_perms |= BLK_PERM_CONSISTENT_READ
| BLK_PERM_WRITE
| BLK_PERM_GRAPH_MOD;
} else if (bdrv_chain_contains(bs, bdrv_skip_filters(target))) {
/*
* We may want to allow this in the future, but it would
* require taking some extra care.
*/
error_setg(errp, "Cannot mirror to a filter on top of a node in the "
"source's backing chain");
goto fail;
}
if (backing_mode != MIRROR_LEAVE_BACKING_CHAIN) {
target_perms |= BLK_PERM_GRAPH_MOD;
}
s->target = blk_new(s->common.job.aio_context,
target_perms, target_shared_perms);
ret = blk_insert_bs(s->target, target, errp);
if (ret < 0) {
goto fail;
}
if (is_mirror) {
/* XXX: Mirror target could be a NBD server of target QEMU in the case
* of non-shared block migration. To allow migration completion, we
* have to allow "inactivate" of the target BB. When that happens, we
* know the job is drained, and the vcpus are stopped, so no write
* operation will be performed. Block layer already has assertions to
* ensure that. */
blk_set_force_allow_inactivate(s->target);
}
blk_set_allow_aio_context_change(s->target, true);
blk_set_disable_request_queuing(s->target, true);
s->replaces = g_strdup(replaces);
s->on_source_error = on_source_error;
s->on_target_error = on_target_error;
s->is_none_mode = is_none_mode;
s->backing_mode = backing_mode;
s->zero_target = zero_target;
s->copy_mode = copy_mode;
s->base = base;
s->base_overlay = bdrv_find_overlay(bs, base);
s->granularity = granularity;
s->buf_size = ROUND_UP(buf_size, granularity);
s->unmap = unmap;
if (auto_complete) {
s->should_complete = true;
}
s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
if (!s->dirty_bitmap) {
goto fail;
}
if (s->copy_mode == MIRROR_COPY_MODE_WRITE_BLOCKING) {
bdrv_disable_dirty_bitmap(s->dirty_bitmap);
}
ret = block_job_add_bdrv(&s->common, "source", bs, 0,
BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE |
BLK_PERM_CONSISTENT_READ,
errp);
if (ret < 0) {
goto fail;
}
/* Required permissions are already taken with blk_new() */
block_job_add_bdrv(&s->common, "target", target, 0, BLK_PERM_ALL,
&error_abort);
/* In commit_active_start() all intermediate nodes disappear, so
* any jobs in them must be blocked */
if (target_is_backing) {
BlockDriverState *iter, *filtered_target;
uint64_t iter_shared_perms;
/*
* The topmost node with
* bdrv_skip_filters(filtered_target) == bdrv_skip_filters(target)
*/
filtered_target = bdrv_cow_bs(bdrv_find_overlay(bs, target));
assert(bdrv_skip_filters(filtered_target) ==
bdrv_skip_filters(target));
/*
* XXX BLK_PERM_WRITE needs to be allowed so we don't block
* ourselves at s->base (if writes are blocked for a node, they are
* also blocked for its backing file). The other options would be a
* second filter driver above s->base (== target).
*/
iter_shared_perms = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE;
for (iter = bdrv_filter_or_cow_bs(bs); iter != target;
iter = bdrv_filter_or_cow_bs(iter))
{
if (iter == filtered_target) {
/*
* From here on, all nodes are filters on the base.
* This allows us to share BLK_PERM_CONSISTENT_READ.
*/
iter_shared_perms |= BLK_PERM_CONSISTENT_READ;
}
ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
iter_shared_perms, errp);
if (ret < 0) {
goto fail;
}
}
if (bdrv_freeze_backing_chain(mirror_top_bs, target, errp) < 0) {
goto fail;
}
}
QTAILQ_INIT(&s->ops_in_flight);
trace_mirror_start(bs, s, opaque);
job_start(&s->common.job);
return &s->common;
fail:
if (s) {
/* Make sure this BDS does not go away until we have completed the graph
* changes below */
bdrv_ref(mirror_top_bs);
g_free(s->replaces);
blk_unref(s->target);
bs_opaque->job = NULL;
if (s->dirty_bitmap) {
bdrv_release_dirty_bitmap(s->dirty_bitmap);
}
job_early_fail(&s->common.job);
}
bs_opaque->stop = true;
bdrv_child_refresh_perms(mirror_top_bs, mirror_top_bs->backing,
&error_abort);
bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, &error_abort);
bdrv_unref(mirror_top_bs);
return NULL;
}
void mirror_start(const char *job_id, BlockDriverState *bs,
BlockDriverState *target, const char *replaces,
int creation_flags, int64_t speed,
uint32_t granularity, int64_t buf_size,
MirrorSyncMode mode, BlockMirrorBackingMode backing_mode,
bool zero_target,
BlockdevOnError on_source_error,
BlockdevOnError on_target_error,
bool unmap, const char *filter_node_name,
MirrorCopyMode copy_mode, Error **errp)
{
bool is_none_mode;
BlockDriverState *base;
if ((mode == MIRROR_SYNC_MODE_INCREMENTAL) ||
(mode == MIRROR_SYNC_MODE_BITMAP)) {
error_setg(errp, "Sync mode '%s' not supported",
MirrorSyncMode_str(mode));
return;
}
is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
base = mode == MIRROR_SYNC_MODE_TOP ? bdrv_backing_chain_next(bs) : NULL;
mirror_start_job(job_id, bs, creation_flags, target, replaces,
speed, granularity, buf_size, backing_mode, zero_target,
on_source_error, on_target_error, unmap, NULL, NULL,
&mirror_job_driver, is_none_mode, base, false,
filter_node_name, true, copy_mode, errp);
}
BlockJob *commit_active_start(const char *job_id, BlockDriverState *bs,
BlockDriverState *base, int creation_flags,
int64_t speed, BlockdevOnError on_error,
const char *filter_node_name,
BlockCompletionFunc *cb, void *opaque,
bool auto_complete, Error **errp)
{
bool base_read_only;
BlockJob *job;
base_read_only = bdrv_is_read_only(base);
if (base_read_only) {
if (bdrv_reopen_set_read_only(base, false, errp) < 0) {
return NULL;
}
}
job = mirror_start_job(
job_id, bs, creation_flags, base, NULL, speed, 0, 0,
MIRROR_LEAVE_BACKING_CHAIN, false,
on_error, on_error, true, cb, opaque,
&commit_active_job_driver, false, base, auto_complete,
filter_node_name, false, MIRROR_COPY_MODE_BACKGROUND,
errp);
if (!job) {
goto error_restore_flags;
}
return job;
error_restore_flags:
/* ignore error and errp for bdrv_reopen, because we want to propagate
* the original error */
if (base_read_only) {
bdrv_reopen_set_read_only(base, true, NULL);
}
return NULL;
}
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