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authorStefano Garzarella <sgarzare@redhat.com>2023-02-14 18:16:21 +0100
committerKevin Wolf <kwolf@redhat.com>2023-02-17 14:33:58 +0100
commit60d90bf43c169b9d1dbcb17ed794b7b02c6862b1 (patch)
treecdfc40390163a6187b0eaff1b72d76e9a2b3b8e4 /block.c
parente7b8d9d038f313c2b9e601609e7d7c3ca6ad0234 (diff)
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block: temporarily hold the new AioContext of bs_top in bdrv_append()
bdrv_append() is called with bs_top AioContext held, but bdrv_attach_child_noperm() could change the AioContext of bs_top. bdrv_replace_node_noperm() calls bdrv_drained_begin() starting from commit 2398747128 ("block: Don't poll in bdrv_replace_child_noperm()"). bdrv_drained_begin() can call BDRV_POLL_WHILE that assumes the new lock is taken, so let's temporarily hold the new AioContext to prevent QEMU from failing in BDRV_POLL_WHILE when it tries to release the wrong AioContext. Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2168209 Reported-by: Aihua Liang <aliang@redhat.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Message-Id: <20230214171621.11574-1-sgarzare@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c23
1 files changed, 23 insertions, 0 deletions
diff --git a/block.c b/block.c
index 122aa9a..0c807d1 100644
--- a/block.c
+++ b/block.c
@@ -5265,6 +5265,8 @@ int bdrv_drop_filter(BlockDriverState *bs, Error **errp)
* child.
*
* This function does not create any image files.
+ *
+ * The caller must hold the AioContext lock for @bs_top.
*/
int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
Error **errp)
@@ -5272,11 +5274,14 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
int ret;
BdrvChild *child;
Transaction *tran = tran_new();
+ AioContext *old_context, *new_context = NULL;
GLOBAL_STATE_CODE();
assert(!bs_new->backing);
+ old_context = bdrv_get_aio_context(bs_top);
+
child = bdrv_attach_child_noperm(bs_new, bs_top, "backing",
&child_of_bds, bdrv_backing_role(bs_new),
tran, errp);
@@ -5285,6 +5290,19 @@ int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
goto out;
}
+ /*
+ * bdrv_attach_child_noperm could change the AioContext of bs_top.
+ * bdrv_replace_node_noperm calls bdrv_drained_begin, so let's temporarily
+ * hold the new AioContext, since bdrv_drained_begin calls BDRV_POLL_WHILE
+ * that assumes the new lock is taken.
+ */
+ new_context = bdrv_get_aio_context(bs_top);
+
+ if (old_context != new_context) {
+ aio_context_release(old_context);
+ aio_context_acquire(new_context);
+ }
+
ret = bdrv_replace_node_noperm(bs_top, bs_new, true, tran, errp);
if (ret < 0) {
goto out;
@@ -5296,6 +5314,11 @@ out:
bdrv_refresh_limits(bs_top, NULL, NULL);
+ if (new_context && old_context != new_context) {
+ aio_context_release(new_context);
+ aio_context_acquire(old_context);
+ }
+
return ret;
}