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block: Fix AioContext locking in bdrv_reopen_parse_file_or_backing() 

bdrv_set_file_or_backing_noperm() requires the caller to hold the
AioContext lock for the child node, but we hold the one for the parent
node in bdrv_reopen_parse_file_or_backing(). Take the other one
temporarily.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20230605085711.21261-7-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2023-06-05 10:57:06 +02:00
parent c066e808e1
commit 4b408668d0
1 changed files with 33 additions and 2 deletions
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35
block.c
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@ -3366,6 +3366,10 @@ static BdrvChildRole bdrv_backing_role(BlockDriverState *bs)
* callers which don't need their own reference any more must call bdrv_unref().
*
* Function doesn't update permissions, caller is responsible for this.
*
* The caller must hold the AioContext lock for @child_bs. Both @parent_bs and
* @child_bs can move to a different AioContext in this function. Callers must
* make sure that their AioContext locking is still correct after this.
*/
static int bdrv_set_file_or_backing_noperm(BlockDriverState *parent_bs,
BlockDriverState *child_bs,
@ -3454,6 +3458,11 @@ out:
return 0;
}
/*
* The caller must hold the AioContext lock for @backing_hd. Both @bs and
* @backing_hd can move to a different AioContext in this function. Callers must
* make sure that their AioContext locking is still correct after this.
*/
static int bdrv_set_backing_noperm(BlockDriverState *bs,
BlockDriverState *backing_hd,
Transaction *tran, Error **errp)
@ -4606,6 +4615,11 @@ int bdrv_reopen_set_read_only(BlockDriverState *bs, bool read_only,
* backing BlockDriverState (or NULL).
*
* Return 0 on success, otherwise return < 0 and set @errp.
*
* The caller must hold the AioContext lock of @reopen_state->bs.
* @reopen_state->bs can move to a different AioContext in this function.
* Callers must make sure that their AioContext locking is still correct after
* this.
*/
static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
bool is_backing, Transaction *tran,
@ -4618,6 +4632,8 @@ static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
const char *child_name = is_backing ? "backing" : "file";
QObject *value;
const char *str;
AioContext *ctx, *old_ctx;
int ret;
GLOBAL_STATE_CODE();
@ -4682,8 +4698,22 @@ static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
reopen_state->old_file_bs = old_child_bs;
}
return bdrv_set_file_or_backing_noperm(bs, new_child_bs, is_backing,
tran, errp);
old_ctx = bdrv_get_aio_context(bs);
ctx = bdrv_get_aio_context(new_child_bs);
if (old_ctx != ctx) {
aio_context_release(old_ctx);
aio_context_acquire(ctx);
}
ret = bdrv_set_file_or_backing_noperm(bs, new_child_bs, is_backing,
tran, errp);
if (old_ctx != ctx) {
aio_context_release(ctx);
aio_context_acquire(old_ctx);
}
return ret;
}
/*
@ -4702,6 +4732,7 @@ static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
* It is the responsibility of the caller to then call the abort() or
* commit() for any other BDS that have been left in a prepare() state
*
* The caller must hold the AioContext lock of @reopen_state->bs.
*/
static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
BlockReopenQueue *queue,