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[Qemu-devel] [PULL 26/35] block: fix overlapping multiwrite requests
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL 26/35] block: fix overlapping multiwrite requests |
Date: |
Fri, 29 Aug 2014 17:29:54 +0100 |
When request A is a strict superset of request B:
AAAAAAAA
BBBB
multiwrite_merge() merges them as follows:
AABBBB
The tail of request A should have been included:
AABBBBAA
This patch fixes data loss but this code path is probably rare. Since
guests cannot assume ordering between in-flight requests, few
applications submit overlapping write requests.
Reported-by: Slava Pestov <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Benoit Canet <address@hidden>
---
block.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/block.c b/block.c
index 9c5566b..cb670fd 100644
--- a/block.c
+++ b/block.c
@@ -4553,6 +4553,12 @@ static int multiwrite_merge(BlockDriverState *bs,
BlockRequest *reqs,
// Add the second request
qemu_iovec_concat(qiov, reqs[i].qiov, 0, reqs[i].qiov->size);
+ // Add tail of first request, if necessary
+ if (qiov->size < reqs[outidx].qiov->size) {
+ qemu_iovec_concat(qiov, reqs[outidx].qiov, qiov->size,
+ reqs[outidx].qiov->size - qiov->size);
+ }
+
reqs[outidx].nb_sectors = qiov->size >> 9;
reqs[outidx].qiov = qiov;
--
1.9.3
- [Qemu-devel] [PULL 15/35] AioContext: run bottom halves after polling, (continued)
- [Qemu-devel] [PULL 15/35] AioContext: run bottom halves after polling, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 16/35] AioContext: export and use aio_dispatch, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 17/35] test-aio: test timers on Windows too, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 18/35] aio-win32: add aio_set_dispatching optimization, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 19/35] AioContext: introduce aio_prepare, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 20/35] qemu-coroutine-io: fix for Win32, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 22/35] sheepdog: fix a core dump while do auto-reconnecting, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 21/35] aio-win32: add support for sockets, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 23/35] nbd: Drop nbd_can_read(), Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 24/35] block: Add AIO context notifiers, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 26/35] block: fix overlapping multiwrite requests,
Stefan Hajnoczi <=
- [Qemu-devel] [PULL 27/35] qemu-iotests: add multiwrite test cases, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 25/35] nbd: Follow the BDS' AIO context, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 29/35] block: acquire AioContext in do_drive_del(), Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 28/35] linux-aio: avoid deadlock in nested aio_poll() calls, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 30/35] virtio-blk: allow drive_del with dataplane, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 32/35] curl: Don't deref NULL pointer in call to aio_poll., Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 33/35] nfs: Fix leak of opts in nfs_file_open, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 31/35] curl: Allow a cookie or cookies to be sent with http/https requests., Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 34/35] blkverify: Fix leak of opts in blkverify_open, Stefan Hajnoczi, 2014/08/29
- [Qemu-devel] [PULL 35/35] quorum: Fix leak of opts in quorum_open, Stefan Hajnoczi, 2014/08/29