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qemu-e2k/block/mirror.c
Kevin Wolf 6bc0bcc89f block: Fix deadlocks in bdrv_graph_wrunlock() 
bdrv_graph_wrunlock() calls aio_poll(), which may run callbacks that
have a nested event loop. Nested event loops can depend on other
iothreads making progress, so in order to allow them to make progress it
must not hold the AioContext lock of another thread while calling
aio_poll().

This introduces a @bs parameter to bdrv_graph_wrunlock() whose
AioContext is temporarily dropped (which matches bdrv_graph_wrlock()),
and a bdrv_graph_wrunlock_ctx() that can be used if the BlockDriverState
doesn't necessarily exist any more when unlocking.

This also requires a change to bdrv_schedule_unref(), which was relying
on the incorrectly taken lock. It needs to take the lock itself now.
While this is a separate bug, it can't be fixed a separate patch because
otherwise the intermediate state would either deadlock or try to release
a lock that we don't even hold.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231115172012.112727-3-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
[kwolf: Fixed up bdrv_schedule_unref()]
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-11-21 12:45:21 +01:00

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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 "block/dirty-bitmap.h"
#include "sysemu/block-backend.h"
#include "qapi/error.h"
#include "qemu/ratelimit.h"
#include "qemu/bitmap.h"
#include "qemu/memalign.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;
/*
* To be accesssed with atomics. Written only under the BQL (required by the
* current implementation of mirror_change()).
*/
MirrorCopyMode copy_mode;
BlockdevOnError on_source_error, on_target_error;
/*
* To be accessed with atomics.
*
* 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;
unsigned 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;
int64_t active_write_bytes_in_flight;
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)
{
qatomic_set(&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 (self) {
/*
* 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);
if (self) {
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 coroutine_fn 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_subclusters(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_free_in_flight_slot(MirrorBlockJob *s)
{
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.
* Also, do not wait on active operations, because they do not
* use up in-flight slots.
*/
if (!op->is_pseudo_op && op->is_in_flight && !op->is_active_write) {
qemu_co_queue_wait(&op->waiting_requests, NULL);
return;
}
}
abort();
}
/* 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);
WITH_GRAPH_RDLOCK_GUARD() {
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 void coroutine_fn GRAPH_RDLOCK mirror_iteration(MirrorBlockJob *s)
{
BlockDriverState *source = s->mirror_top_bs->backing->bs;
MirrorOp *pseudo_op;
int64_t offset;
/* 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);
/*
* Wait for concurrent requests to @offset. The next loop will limit the
* copied area based on in_flight_bitmap so we only copy an area that does
* not overlap with concurrent in-flight requests. Still, we would like to
* copy something, so wait until there are at least no more requests to the
* very beginning of the area.
*/
mirror_wait_on_conflicts(NULL, s, offset, 1);
job_pause_point(&s->common.job);
/* Find the number of consecutive 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));
WITH_GRAPH_RDLOCK_GUARD() {
ret = bdrv_co_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;
WITH_GRAPH_RDLOCK_GUARD() {
bdrv_round_to_subclusters(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);
block_job_ratelimit_processed_bytes(&s->common, io_bytes_acct);
}
fail:
QTAILQ_REMOVE(&s->ops_in_flight, pseudo_op, next);
qemu_co_queue_restart_all(&pseudo_op->waiting_requests);
g_free(pseudo_op);
}
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;
GLOBAL_STATE_CODE();
if (s->prepared) {
return 0;
}
s->prepared = true;
aio_context_acquire(qemu_get_aio_context());
bdrv_graph_rdlock_main_loop();
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);
bdrv_graph_rdunlock_main_loop();
/*
* 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);
bdrv_drained_begin(target_bs);
bs_opaque->stop = true;
bdrv_graph_rdlock_main_loop();
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;
}
}
bdrv_graph_rdunlock_main_loop();
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(to_replace);
/*
* Cannot use check_to_replace_node() here, because that would
* check for an op blocker on @to_replace, and we have our own
* there.
*/
bdrv_graph_wrlock(target_bs);
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_graph_wrunlock(target_bs);
bdrv_drained_end(to_replace);
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);
/*
* 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_graph_wrlock(mirror_top_bs);
bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, &error_abort);
bdrv_graph_wrunlock(mirror_top_bs);
bdrv_drained_end(target_bs);
bdrv_unref(target_bs);
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);
aio_context_release(qemu_get_aio_context());
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 GRAPH_UNLOCKED mirror_dirty_init(MirrorBlockJob *s)
{
int64_t offset;
BlockDriverState *bs;
BlockDriverState *target_bs = blk_bs(s->target);
int ret;
int64_t count;
bdrv_graph_co_rdlock();
bs = s->mirror_top_bs->backing->bs;
bdrv_graph_co_rdunlock();
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;
}
WITH_GRAPH_RDLOCK_GUARD() {
ret = bdrv_co_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 coroutine_fn mirror_flush(MirrorBlockJob *s)
{
int ret = blk_co_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;
MirrorBDSOpaque *mirror_top_opaque = s->mirror_top_bs->opaque;
BlockDriverState *target_bs = blk_bs(s->target);
bool need_drain = true;
BlockDeviceIoStatus iostatus;
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;
bdrv_graph_co_rdlock();
bs = bdrv_filter_bs(s->mirror_top_bs);
bdrv_graph_co_rdunlock();
if (job_is_cancelled(&s->common.job)) {
goto immediate_exit;
}
bdrv_graph_co_rdlock();
s->bdev_length = bdrv_co_getlength(bs);
bdrv_graph_co_rdunlock();
if (s->bdev_length < 0) {
ret = s->bdev_length;
goto immediate_exit;
}
target_length = blk_co_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_co_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);
qatomic_set(&s->actively_synced, true);
while (!job_cancel_requested(&s->common.job) && !s->should_complete) {
job_yield(&s->common.job);
}
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));
bdrv_graph_co_rdlock();
if (!bdrv_co_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);
bdrv_graph_co_rdunlock();
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;
}
}
/*
* Only now the job is fully initialised and mirror_top_bs should start
* accessing it.
*/
mirror_top_opaque->job = s;
assert(!s->dbi);
s->dbi = bdrv_dirty_iter_new(s->dirty_bitmap);
for (;;) {
int64_t cnt, delta;
bool should_complete;
if (s->ret < 0) {
ret = s->ret;
goto immediate_exit;
}
job_pause_point(&s->common.job);
if (job_is_cancelled(&s->common.job)) {
ret = 0;
goto immediate_exit;
}
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 +
s->active_write_bytes_in_flight);
/* 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;
WITH_JOB_LOCK_GUARD() {
iostatus = s->common.iostatus;
}
if (delta < BLOCK_JOB_SLICE_TIME &&
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) {
bdrv_graph_co_rdlock();
mirror_iteration(s);
bdrv_graph_co_rdunlock();
}
}
should_complete = false;
if (s->in_flight == 0 && cnt == 0) {
trace_mirror_before_flush(s);
if (!job_is_ready(&s->common.job)) {
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);
}
if (qatomic_read(&s->copy_mode) != MIRROR_COPY_MODE_BACKGROUND) {
qatomic_set(&s->actively_synced, true);
}
should_complete = s->should_complete ||
job_cancel_requested(&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);
/* Must be zero because we are drained */
assert(s->in_active_write_counter == 0);
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));
need_drain = false;
break;
}
if (job_is_ready(&s->common.job) && !should_complete) {
if (s->in_flight == 0 && cnt == 0) {
trace_mirror_before_sleep(s, cnt, job_is_ready(&s->common.job),
BLOCK_JOB_SLICE_TIME);
job_sleep_ns(&s->common.job, BLOCK_JOB_SLICE_TIME);
}
} else {
block_job_ratelimit_sleep(&s->common);
}
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 || 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 (!job_is_ready(job)) {
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 child freeze system. */
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 */
WITH_JOB_LOCK_GUARD() {
if (!job->paused) {
job_enter_cond_locked(job, NULL);
}
}
}
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.
*/
WITH_JOB_LOCK_GUARD() {
if (!s->common.job.paused && !job_is_cancelled_locked(&job->job)
&& !s->in_drain) {
return true;
}
}
return !!s->in_flight;
}
static bool mirror_cancel(Job *job, bool force)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job);
BlockDriverState *target = blk_bs(s->target);
/*
* Before the job is READY, we treat any cancellation like a
* force-cancellation.
*/
force = force || !job_is_ready(job);
if (force) {
bdrv_cancel_in_flight(target);
}
return force;
}
static bool commit_active_cancel(Job *job, bool force)
{
/* Same as above in mirror_cancel() */
return force || !job_is_ready(job);
}
static void mirror_change(BlockJob *job, BlockJobChangeOptions *opts,
Error **errp)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
BlockJobChangeOptionsMirror *change_opts = &opts->u.mirror;
MirrorCopyMode current;
/*
* The implementation relies on the fact that copy_mode is only written
* under the BQL. Otherwise, further synchronization would be required.
*/
GLOBAL_STATE_CODE();
if (qatomic_read(&s->copy_mode) == change_opts->copy_mode) {
return;
}
if (change_opts->copy_mode != MIRROR_COPY_MODE_WRITE_BLOCKING) {
error_setg(errp, "Change to copy mode '%s' is not implemented",
MirrorCopyMode_str(change_opts->copy_mode));
return;
}
current = qatomic_cmpxchg(&s->copy_mode, MIRROR_COPY_MODE_BACKGROUND,
change_opts->copy_mode);
if (current != MIRROR_COPY_MODE_BACKGROUND) {
error_setg(errp, "Expected current copy mode '%s', got '%s'",
MirrorCopyMode_str(MIRROR_COPY_MODE_BACKGROUND),
MirrorCopyMode_str(current));
}
}
static void mirror_query(BlockJob *job, BlockJobInfo *info)
{
MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
info->u.mirror = (BlockJobInfoMirror) {
.actively_synced = qatomic_read(&s->actively_synced),
};
}
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,
.change = mirror_change,
.query = mirror_query,
};
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,
.cancel = commit_active_cancel,
},
.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);
job->active_write_bytes_in_flight += 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();
}
job->active_write_bytes_in_flight -= bytes;
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);
qatomic_set(&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++;
/*
* Wait for concurrent requests affecting the area. If there are already
* running requests that are copying off now-to-be stale data in the area,
* we must wait for them to finish before we begin writing fresh data to the
* target so that the write operations appear in the correct order.
* Note that background requests (see mirror_iteration()) in contrast only
* wait for conflicting requests at the start of the dirty area, and then
* (based on the in_flight_bitmap) truncate the area to copy so it will not
* conflict with any requests beyond that. For active writes, however, we
* cannot truncate that area. The request from our parent must be blocked
* until the area is copied in full. Therefore, we must wait for the whole
* area to become free of concurrent requests.
*/
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 GRAPH_RDLOCK 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 &&
qatomic_read(&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 GRAPH_RDLOCK
bdrv_mirror_top_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, BdrvRequestFlags flags)
{
return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
}
static bool should_copy_to_target(MirrorBDSOpaque *s)
{
return s->job && s->job->ret >= 0 &&
!job_is_cancelled(&s->job->common.job) &&
qatomic_read(&s->job->copy_mode) == MIRROR_COPY_MODE_WRITE_BLOCKING;
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_mirror_top_do_write(BlockDriverState *bs, MirrorMethod method,
bool copy_to_target, uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
MirrorOp *op = NULL;
MirrorBDSOpaque *s = bs->opaque;
int ret = 0;
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 (!copy_to_target && s->job && s->job->dirty_bitmap) {
qatomic_set(&s->job->actively_synced, false);
bdrv_set_dirty_bitmap(s->job->dirty_bitmap, offset, bytes);
}
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 GRAPH_RDLOCK
bdrv_mirror_top_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
QEMUIOVector *qiov, BdrvRequestFlags flags)
{
QEMUIOVector bounce_qiov;
void *bounce_buf;
int ret = 0;
bool copy_to_target = should_copy_to_target(bs->opaque);
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;
flags &= ~BDRV_REQ_REGISTERED_BUF;
}
ret = bdrv_mirror_top_do_write(bs, MIRROR_METHOD_COPY, copy_to_target,
offset, bytes, qiov, flags);
if (copy_to_target) {
qemu_iovec_destroy(&bounce_qiov);
qemu_vfree(bounce_buf);
}
return ret;
}
static int coroutine_fn GRAPH_RDLOCK 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 GRAPH_RDLOCK
bdrv_mirror_top_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
int64_t bytes, BdrvRequestFlags flags)
{
bool copy_to_target = should_copy_to_target(bs->opaque);
return bdrv_mirror_top_do_write(bs, MIRROR_METHOD_ZERO, copy_to_target,
offset, bytes, NULL, flags);
}
static int coroutine_fn GRAPH_RDLOCK
bdrv_mirror_top_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
{
bool copy_to_target = should_copy_to_target(bs->opaque);
return bdrv_mirror_top_do_write(bs, MIRROR_METHOD_DISCARD, copy_to_target,
offset, bytes, NULL, 0);
}
static void GRAPH_RDLOCK 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,
.filtered_child_is_backing = 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;
GLOBAL_STATE_CODE();
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;
}
bdrv_graph_rdlock_main_loop();
if (bdrv_skip_filters(bs) == bdrv_skip_filters(target)) {
error_setg(errp, "Can't mirror node into itself");
bdrv_graph_rdunlock_main_loop();
return NULL;
}
target_is_backing = bdrv_chain_contains(bs, target);
bdrv_graph_rdunlock_main_loop();
/* 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, speed,
creation_flags, cb, opaque, errp);
if (!s) {
goto fail;
}
/* 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;
} else {
bdrv_graph_rdlock_main_loop();
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");
bdrv_graph_rdunlock_main_loop();
goto fail;
}
bdrv_graph_rdunlock_main_loop();
}
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);
bdrv_graph_rdlock_main_loop();
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;
qatomic_set(&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;
}
bdrv_graph_rdunlock_main_loop();
s->dirty_bitmap = bdrv_create_dirty_bitmap(s->mirror_top_bs, granularity,
NULL, errp);
if (!s->dirty_bitmap) {
goto fail;
}
/*
* The dirty bitmap is set by bdrv_mirror_top_do_write() when not in active
* mode.
*/
bdrv_disable_dirty_bitmap(s->dirty_bitmap);
bdrv_graph_wrlock(bs);
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) {
bdrv_graph_wrunlock(bs);
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) {
bdrv_graph_wrunlock(bs);
goto fail;
}
}
if (bdrv_freeze_backing_chain(mirror_top_bs, target, errp) < 0) {
bdrv_graph_wrunlock(bs);
goto fail;
}
}
bdrv_graph_wrunlock(bs);
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_drained_begin(bs);
bdrv_graph_wrlock(bs);
assert(mirror_top_bs->backing->bs == bs);
bdrv_child_refresh_perms(mirror_top_bs, mirror_top_bs->backing,
&error_abort);
bdrv_replace_node(mirror_top_bs, bs, &error_abort);
bdrv_graph_wrunlock(bs);
bdrv_drained_end(bs);
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;
GLOBAL_STATE_CODE();
if ((mode == MIRROR_SYNC_MODE_INCREMENTAL) ||
(mode == MIRROR_SYNC_MODE_BITMAP)) {
error_setg(errp, "Sync mode '%s' not supported",
MirrorSyncMode_str(mode));
return;
}
bdrv_graph_rdlock_main_loop();
is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
base = mode == MIRROR_SYNC_MODE_TOP ? bdrv_backing_chain_next(bs) : NULL;
bdrv_graph_rdunlock_main_loop();
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;
GLOBAL_STATE_CODE();
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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