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[Qemu-devel] [PULL 05/15] mirror: Drop permissions on s->target on compl
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 05/15] mirror: Drop permissions on s->target on completion |
Date: |
Mon, 29 May 2017 17:06:44 +0200 |
This fixes an assertion failure that was triggered by qemu-iotests 129
on some CI host, while the same test case didn't seem to fail on other
hosts.
Essentially the problem is that the blk_unref(s->target) in
mirror_exit() doesn't necessarily mean that the BlockBackend goes away
immediately. It is possible that the job completion was triggered nested
in mirror_drain(), which looks like this:
BlockBackend *target = s->target;
blk_ref(target);
blk_drain(target);
blk_unref(target);
In this case, the write permissions for s->target are retained until
after blk_drain(), which makes removing mirror_top_bs fail for the
active commit case (can't have a writable backing file in the chain
without the filter driver).
Explicitly dropping the permissions first means that the additional
reference doesn't hurt and the job can complete successfully even if
called from the nested blk_drain().
Cc: address@hidden
Signed-off-by: Kevin Wolf <address@hidden>
Acked-by: Paolo Bonzini <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
---
block/mirror.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/block/mirror.c b/block/mirror.c
index e86f8f8..e778ee0 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -514,7 +514,12 @@ static void mirror_exit(BlockJob *job, void *opaque)
/* Remove target parent that still uses BLK_PERM_WRITE/RESIZE before
* inserting target_bs at s->to_replace, where we might not be able to get
- * these permissions. */
+ * these permissions.
+ *
+ * Note that blk_unref() alone doesn't necessarily drop permissions because
+ * we might be running nested inside mirror_drain(), which takes an extra
+ * reference, so use an explicit blk_set_perm() first. */
+ blk_set_perm(s->target, 0, BLK_PERM_ALL, &error_abort);
blk_unref(s->target);
s->target = NULL;
--
1.8.3.1
- [Qemu-devel] [PULL 00/15] Block layer patches, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 02/15] qemu-iotests: Test streaming with missing job ID, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 03/15] iotests: 147: Don't test inet6 if not available, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 01/15] stream: fix crash in stream_start() when block_job_create() fails, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 05/15] mirror: Drop permissions on s->target on completion,
Kevin Wolf <=
- [Qemu-devel] [PULL 04/15] nvme: Add support for Controller Memory Buffers, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 08/15] qemu-img: add support for --object with 'dd' command, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 06/15] qcow2: remove extra local_error variable, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 09/15] qemu-img: fix --image-opts usage with dd command, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 07/15] qemu-img: Fix documentation of convert, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 10/15] qemu-img: introduce --target-image-opts for 'convert' command, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 11/15] qemu-img: copy *key-secret opts when opening newly created files, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 13/15] block: Tweak error message related to qemu-img amend, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 12/15] qemu-img: Fix leakage of options on error, Kevin Wolf, 2017/05/29
- [Qemu-devel] [PULL 14/15] block: Fix backing paths for filenames with colons, Kevin Wolf, 2017/05/29