diff options
| author | Alberto Garcia <berto@igalia.com> | 2015-10-28 15:43:49 +0200 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2015-11-11 16:25:47 +0100 |
| commit | 3db2bd5508c86a1605258bc77c9672d93b5c350e (patch) | |
| tree | 430d334eb2a56fe4b7063933fa0d641fb94fbdf0 /block | |
| parent | 89e3a2d86d31212d09ca688193ccecb92c0c77b5 (diff) | |
commit: reopen overlay_bs before base
'block-commit' needs write access to two different nodes of the chain:
- 'base', because that's where the data is written to.
- the overlay of 'top', because it needs to update the backing file
string to point to 'base' after the operation.
Both images have to be opened in read-write mode, and commit_start()
takes care of reopening them if necessary.
With the current implementation, however, when overlay_bs is reopened
in read-write mode it has the side effect of making 'base' read-only
again, eventually making 'block-commit' fail.
This needs to be fixed in bdrv_reopen(), but until we get to that it
can be worked around simply by swapping the order of base and
overlay_bs in the reopen queue.
In order to reproduce this bug, overlay_bs needs to be initially in
read-only mode. That is: the 'top' parameter of 'block-commit' cannot
be the active layer nor its immediate backing chain.
Cc: qemu-stable@nongnu.org
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/commit.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/block/commit.c b/block/commit.c index fdebe87c16..a5d02aa560 100644 --- a/block/commit.c +++ b/block/commit.c @@ -236,14 +236,14 @@ void commit_start(BlockDriverState *bs, BlockDriverState *base, orig_overlay_flags = bdrv_get_flags(overlay_bs); /* convert base & overlay_bs to r/w, if necessary */ - if (!(orig_base_flags & BDRV_O_RDWR)) { - reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL, - orig_base_flags | BDRV_O_RDWR); - } if (!(orig_overlay_flags & BDRV_O_RDWR)) { reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs, NULL, orig_overlay_flags | BDRV_O_RDWR); } + if (!(orig_base_flags & BDRV_O_RDWR)) { + reopen_queue = bdrv_reopen_queue(reopen_queue, base, NULL, + orig_base_flags | BDRV_O_RDWR); + } if (reopen_queue) { bdrv_reopen_multiple(reopen_queue, &local_err); if (local_err != NULL) { |