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blockdev: mirror: avoid potential deadlock when using iothread

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The bdrv_getlength() function is a generated co-wrapper and uses
AIO_WAIT_WHILE() to wait for the spawned coroutine. AIO_WAIT_WHILE()
expects the lock to be acquired exactly once.

Fix a case where it may be acquired twice. This can happen when the
source node is explicitly specified as the @replaces parameter or if the
source node is a filter node.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20231019131936.414246-4-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 2023-10-19 15:19:36 +02:00 committed by Kevin Wolf
parent e462c6d27d
commit 302823854b
1 changed files with 12 additions and 2 deletions
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14
blockdev.c
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@ -2968,6 +2968,7 @@ static void blockdev_mirror_common(const char *job_id, BlockDriverState *bs,
if (replaces) {
BlockDriverState *to_replace_bs;
AioContext *aio_context;
AioContext *replace_aio_context;
int64_t bs_size, replace_size;
@ -2982,10 +2983,19 @@ static void blockdev_mirror_common(const char *job_id, BlockDriverState *bs,
return;
}
aio_context = bdrv_get_aio_context(bs);
replace_aio_context = bdrv_get_aio_context(to_replace_bs);
aio_context_acquire(replace_aio_context);
/*
* bdrv_getlength() is a co-wrapper and uses AIO_WAIT_WHILE. Be sure not
* to acquire the same AioContext twice.
*/
if (replace_aio_context != aio_context) {
aio_context_acquire(replace_aio_context);
}
replace_size = bdrv_getlength(to_replace_bs);
aio_context_release(replace_aio_context);
if (replace_aio_context != aio_context) {
aio_context_release(replace_aio_context);
}
if (replace_size < 0) {
error_setg_errno(errp, -replace_size,