mirror: Drop redundant zero_target parameter
The two callers to a mirror job (drive-mirror and blockdev-mirror) set
zero_target precisely when sync mode == FULL, with the one exception
that drive-mirror skips zeroing the target if it was newly created and
reads as zero. But given the previous patch, that exception is
equally captured by target_is_zero.
Meanwhile, there is another slight wrinkle, fortunately caught by
iotest 185: if the caller uses "sync":"top" but the source has no
backing file, the code in blockdev.c was changing sync to be FULL, but
only after it had set zero_target=false. In mirror.c, prior to recent
patches, this didn't matter: the only places that inspected sync were
setting is_none_mode (both TOP and FULL had set that to false), and
mirror_start() setting base = mode == MIRROR_SYNC_MODE_TOP ?
bdrv_backing_chain_next(bs) : NULL. But now that we are passing sync
around, the slammed sync mode would result in a new pre-zeroing pass
even when the user had passed "sync":"top" in an effort to skip
pre-zeroing. Fortunately, the assignment of base when bs has no
backing chain still works out to NULL if we don't slam things. So
with the forced change of sync ripped out of blockdev.c, the sync mode
is passed through the full callstack unmolested, and we can now
reliably reconstruct the same settings as what used to be passed in by
zero_target=false, without the redundant parameter.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20250509204341.3553601-24-eblake@redhat.com>
Reviewed-by: Sunny Zhu <sunnyzhyy@qq.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
[eblake: Fix regression in iotest 185]
Signed-off-by: Eric Blake <eblake@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 97128fe..21443b4 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2804,7 +2804,7 @@
const char *replaces,
enum MirrorSyncMode sync,
BlockMirrorBackingMode backing_mode,
- bool zero_target, bool target_is_zero,
+ bool target_is_zero,
bool has_speed, int64_t speed,
bool has_granularity, uint32_t granularity,
bool has_buf_size, int64_t buf_size,
@@ -2871,10 +2871,6 @@
return;
}
- if (!bdrv_backing_chain_next(bs) && sync == MIRROR_SYNC_MODE_TOP) {
- sync = MIRROR_SYNC_MODE_FULL;
- }
-
if (!replaces) {
/* We want to mirror from @bs, but keep implicit filters on top */
unfiltered_bs = bdrv_skip_implicit_filters(bs);
@@ -2916,7 +2912,7 @@
* and will allow to check whether the node still exist at mirror completion
*/
mirror_start(job_id, bs, target, replaces, job_flags,
- speed, granularity, buf_size, sync, backing_mode, zero_target,
+ speed, granularity, buf_size, sync, backing_mode,
target_is_zero, on_source_error, on_target_error, unmap,
filter_node_name, copy_mode, errp);
}
@@ -2932,7 +2928,6 @@
int flags;
int64_t size;
const char *format = arg->format;
- bool zero_target;
bool target_is_zero;
int ret;
@@ -3047,9 +3042,6 @@
}
bdrv_graph_rdlock_main_loop();
- zero_target = (arg->sync == MIRROR_SYNC_MODE_FULL &&
- (arg->mode == NEW_IMAGE_MODE_EXISTING ||
- !bdrv_has_zero_init(target_bs)));
target_is_zero = (arg->mode != NEW_IMAGE_MODE_EXISTING &&
bdrv_has_zero_init(target_bs));
bdrv_graph_rdunlock_main_loop();
@@ -3063,7 +3055,7 @@
blockdev_mirror_common(arg->job_id, bs, target_bs,
arg->replaces, arg->sync,
- backing_mode, zero_target, target_is_zero,
+ backing_mode, target_is_zero,
arg->has_speed, arg->speed,
arg->has_granularity, arg->granularity,
arg->has_buf_size, arg->buf_size,
@@ -3100,7 +3092,6 @@
BlockDriverState *target_bs;
AioContext *aio_context;
BlockMirrorBackingMode backing_mode = MIRROR_LEAVE_BACKING_CHAIN;
- bool zero_target;
int ret;
bs = qmp_get_root_bs(device, errp);
@@ -3113,8 +3104,6 @@
return;
}
- zero_target = (sync == MIRROR_SYNC_MODE_FULL);
-
aio_context = bdrv_get_aio_context(bs);
ret = bdrv_try_change_aio_context(target_bs, aio_context, NULL, errp);
@@ -3124,7 +3113,7 @@
blockdev_mirror_common(job_id, bs, target_bs,
replaces, sync, backing_mode,
- zero_target, has_target_is_zero && target_is_zero,
+ has_target_is_zero && target_is_zero,
has_speed, speed,
has_granularity, granularity,
has_buf_size, buf_size,