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block: Fix AioContext locking in bdrv_open_child() 

bdrv_attach_child() requires that the caller holds the AioContext lock
for the new child node. Take it in bdrv_open_child() and document that
the caller must not hold any AioContext apart from the main AioContext.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20230605085711.21261-5-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 10:57:04 +02:00
parent 2065cf6b23
commit 8394c35ee1
1 changed files with 11 additions and 2 deletions
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11
block.c
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@ -3654,6 +3654,7 @@ done:
* *
* The BlockdevRef will be removed from the options QDict. * The BlockdevRef will be removed from the options QDict.
* *
* The caller must hold the lock of the main AioContext and no other AioContext.
* @parent can move to a different AioContext in this function. Callers must * @parent can move to a different AioContext in this function. Callers must
* make sure that their AioContext locking is still correct after this. * make sure that their AioContext locking is still correct after this.
*/ */
@ -3665,6 +3666,8 @@ BdrvChild *bdrv_open_child(const char *filename,
bool allow_none, Error **errp) bool allow_none, Error **errp)
{ {
BlockDriverState *bs; BlockDriverState *bs;
BdrvChild *child;
AioContext *ctx;
GLOBAL_STATE_CODE(); GLOBAL_STATE_CODE();
@ -3674,13 +3677,19 @@ BdrvChild *bdrv_open_child(const char *filename,
return NULL; return NULL;
} }
return bdrv_attach_child(parent, bs, bdref_key, child_class, child_role, ctx = bdrv_get_aio_context(bs);
aio_context_acquire(ctx);
child = bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
errp); errp);
aio_context_release(ctx);
return child;
} }
/* /*
* Wrapper on bdrv_open_child() for most popular case: open primary child of bs. * Wrapper on bdrv_open_child() for most popular case: open primary child of bs.
* *
* The caller must hold the lock of the main AioContext and no other AioContext.
* @parent can move to a different AioContext in this function. Callers must * @parent can move to a different AioContext in this function. Callers must
* make sure that their AioContext locking is still correct after this. * make sure that their AioContext locking is still correct after this.
*/ */