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blockdev: avoid locking and draining multiple times in external_snapshot_abort()

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By using the appropriate variants bdrv_set_backing_hd_drained() and
bdrv_try_change_aio_context_locked(), there only needs to be a single
drained and write-locked section in external_snapshot_abort().

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-30-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Fiona Ebner
2025-05-30 17:11:06 +02:00
committed by Kevin Wolf
parent de0d24c711
commit c7af387c7b
1 changed files with 14 additions and 8 deletions
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blockdev.c
+14 -8
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@@ -1580,11 +1580,19 @@ static void external_snapshot_abort(void *opaque)
AioContext *tmp_context;
int ret;
bdrv_graph_wrlock_drained();
aio_context = bdrv_get_aio_context(state->old_bs);
bdrv_ref(state->old_bs); /* we can't let bdrv_set_backind_hd()
close state->old_bs; we need it */
bdrv_set_backing_hd(state->new_bs, NULL, &error_abort);
/*
* Note that state->old_bs would not disappear during the
* write-locked section, because the unref from
* bdrv_set_backing_hd_drained() only happens at the end of the
* write-locked section. However, just be explicit about keeping a
* reference and don't rely on that implicit detail.
*/
bdrv_ref(state->old_bs);
bdrv_set_backing_hd_drained(state->new_bs, NULL, &error_abort);
/*
* The call to bdrv_set_backing_hd() above returns state->old_bs to
@@ -1593,16 +1601,14 @@ static void external_snapshot_abort(void *opaque)
*/
tmp_context = bdrv_get_aio_context(state->old_bs);
if (aio_context != tmp_context) {
ret = bdrv_try_change_aio_context(state->old_bs,
aio_context, NULL, NULL);
ret = bdrv_try_change_aio_context_locked(state->old_bs,
aio_context, NULL,
NULL);
assert(ret == 0);
}
bdrv_drained_begin(state->new_bs);
bdrv_graph_wrlock();
bdrv_replace_node(state->new_bs, state->old_bs, &error_abort);
bdrv_graph_wrunlock();
bdrv_drained_end(state->new_bs);
bdrv_unref(state->old_bs); /* bdrv_replace_node() ref'ed old_bs */
}