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mirror: Fix bdrv_has_zero_init() use
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bdrv_has_zero_init() only has meaning for newly created images or image
areas.  If the mirror job itself did not create the image, it cannot
rely on bdrv_has_zero_init()'s result to carry any meaning.

This is the case for drive-mirror with mode=existing and always for
blockdev-mirror.

Note that we only have to zero-initialize the target with sync=full,
because other modes actually do not promise that the target will contain
the same data as the source after the job -- sync=top only promises to
copy anything allocated in the top layer, and sync=none will only copy
new I/O.  (Which is how mirror has always handled it.)

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190724171239.8764-3-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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@XanClic
XanClic committed Aug 19, 2019
1 parent 4d7c487 commit cdf3bc9
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Showing 4 changed files with 24 additions and 7 deletions.
11 changes: 8 additions & 3 deletions block/mirror.c
View file
Expand Up @@ -51,6 +51,8 @@ typedef struct MirrorBlockJob {
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;
Expand Down Expand Up @@ -767,7 +769,7 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
int ret;
int64_t count;

if (base == NULL && !bdrv_has_zero_init(target_bs)) {
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;
Expand Down Expand Up @@ -1515,6 +1517,7 @@ static BlockJob *mirror_start_job(
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,
Expand Down Expand Up @@ -1643,6 +1646,7 @@ static BlockJob *mirror_start_job(
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->granularity = granularity;
Expand Down Expand Up @@ -1747,6 +1751,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
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,
Expand All @@ -1764,7 +1769,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
base = mode == MIRROR_SYNC_MODE_TOP ? backing_bs(bs) : NULL;
mirror_start_job(job_id, bs, creation_flags, target, replaces,
speed, granularity, buf_size, backing_mode,
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);
Expand All @@ -1791,7 +1796,7 @@ BlockJob *commit_active_start(const char *job_id, BlockDriverState *bs,

ret = mirror_start_job(
job_id, bs, creation_flags, base, NULL, speed, 0, 0,
MIRROR_LEAVE_BACKING_CHAIN,
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,
Expand Down
16 changes: 13 additions & 3 deletions blockdev.c
View file
Expand Up @@ -3782,6 +3782,7 @@ static void blockdev_mirror_common(const char *job_id, BlockDriverState *bs,
bool has_replaces, const char *replaces,
enum MirrorSyncMode sync,
BlockMirrorBackingMode backing_mode,
bool zero_target,
bool has_speed, int64_t speed,
bool has_granularity, uint32_t granularity,
bool has_buf_size, int64_t buf_size,
Expand Down Expand Up @@ -3890,7 +3891,7 @@ static void blockdev_mirror_common(const char *job_id, BlockDriverState *bs,
*/
mirror_start(job_id, bs, target,
has_replaces ? replaces : NULL, job_flags,
speed, granularity, buf_size, sync, backing_mode,
speed, granularity, buf_size, sync, backing_mode, zero_target,
on_source_error, on_target_error, unmap, filter_node_name,
copy_mode, errp);
}
Expand All @@ -3906,6 +3907,7 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)
int flags;
int64_t size;
const char *format = arg->format;
bool zero_target;
int ret;

bs = qmp_get_root_bs(arg->device, errp);
Expand Down Expand Up @@ -4007,6 +4009,10 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)
goto out;
}

zero_target = (arg->sync == MIRROR_SYNC_MODE_FULL &&
(arg->mode == NEW_IMAGE_MODE_EXISTING ||
!bdrv_has_zero_init(target_bs)));

ret = bdrv_try_set_aio_context(target_bs, aio_context, errp);
if (ret < 0) {
bdrv_unref(target_bs);
Expand All @@ -4015,7 +4021,8 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)

blockdev_mirror_common(arg->has_job_id ? arg->job_id : NULL, bs, target_bs,
arg->has_replaces, arg->replaces, arg->sync,
backing_mode, arg->has_speed, arg->speed,
backing_mode, zero_target,
arg->has_speed, arg->speed,
arg->has_granularity, arg->granularity,
arg->has_buf_size, arg->buf_size,
arg->has_on_source_error, arg->on_source_error,
Expand Down Expand Up @@ -4055,6 +4062,7 @@ void qmp_blockdev_mirror(bool has_job_id, const char *job_id,
AioContext *aio_context;
BlockMirrorBackingMode backing_mode = MIRROR_LEAVE_BACKING_CHAIN;
Error *local_err = NULL;
bool zero_target;
int ret;

bs = qmp_get_root_bs(device, errp);
Expand All @@ -4067,6 +4075,8 @@ void qmp_blockdev_mirror(bool has_job_id, const char *job_id,
return;
}

zero_target = (sync == MIRROR_SYNC_MODE_FULL);

aio_context = bdrv_get_aio_context(bs);
aio_context_acquire(aio_context);

Expand All @@ -4077,7 +4087,7 @@ void qmp_blockdev_mirror(bool has_job_id, const char *job_id,

blockdev_mirror_common(has_job_id ? job_id : NULL, bs, target_bs,
has_replaces, replaces, sync, backing_mode,
has_speed, speed,
zero_target, has_speed, speed,
has_granularity, granularity,
has_buf_size, buf_size,
has_on_source_error, on_source_error,
Expand Down
2 changes: 2 additions & 0 deletions include/block/block_int.h
View file
Expand Up @@ -1115,6 +1115,7 @@ BlockJob *commit_active_start(const char *job_id, BlockDriverState *bs,
* @buf_size: The amount of data that can be in flight at one time.
* @mode: Whether to collapse all images in the chain to the target.
* @backing_mode: How to establish the target's backing chain after completion.
* @zero_target: Whether the target should be explicitly zero-initialized
* @on_source_error: The action to take upon error reading from the source.
* @on_target_error: The action to take upon error writing to the target.
* @unmap: Whether to unmap target where source sectors only contain zeroes.
Expand All @@ -1134,6 +1135,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
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,
Expand Down
2 changes: 1 addition & 1 deletion tests/test-block-iothread.c
View file
Expand Up @@ -612,7 +612,7 @@ static void test_propagate_mirror(void)

/* Start a mirror job */
mirror_start("job0", src, target, NULL, JOB_DEFAULT, 0, 0, 0,
MIRROR_SYNC_MODE_NONE, MIRROR_OPEN_BACKING_CHAIN,
MIRROR_SYNC_MODE_NONE, MIRROR_OPEN_BACKING_CHAIN, false,
BLOCKDEV_ON_ERROR_REPORT, BLOCKDEV_ON_ERROR_REPORT,
false, "filter_node", MIRROR_COPY_MODE_BACKGROUND,
&error_abort);
Expand Down

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