[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH 4/8] block: fix sector comparism in multiwrite_req_c
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 4/8] block: fix sector comparism in multiwrite_req_compare |
Date: |
Thu, 20 May 2010 15:10:39 +0200 |
From: Christoph Hellwig <address@hidden>
The difference between the start sectors of two requests can be larger
than the size of the "int" type, which can lead to a not correctly
sorted multiwrite array and thus spurious I/O errors and filesystem
corruption due to incorrect request merges.
So instead of doing the cute sector arithmetics trick spell out the
exact comparisms.
Spotted by Kevin Wolf based on a testcase from Michael Tokarev.
Signed-off-by: Christoph Hellwig <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
block.c | 14 +++++++++++++-
1 files changed, 13 insertions(+), 1 deletions(-)
diff --git a/block.c b/block.c
index bfe46e3..89eece7 100644
--- a/block.c
+++ b/block.c
@@ -1929,7 +1929,19 @@ static void multiwrite_cb(void *opaque, int ret)
static int multiwrite_req_compare(const void *a, const void *b)
{
- return (((BlockRequest*) a)->sector - ((BlockRequest*) b)->sector);
+ const BlockRequest *req1 = a, *req2 = b;
+
+ /*
+ * Note that we can't simply subtract req2->sector from req1->sector
+ * here as that could overflow the return value.
+ */
+ if (req1->sector > req2->sector) {
+ return 1;
+ } else if (req1->sector < req2->sector) {
+ return -1;
+ } else {
+ return 0;
+ }
}
/*
--
1.6.6.1
- [Qemu-devel] [PULL 0/8] Block patches, Kevin Wolf, 2010/05/20
- [Qemu-devel] [PATCH 2/8] virtio-blk: Avoid zeroing every request structure, Kevin Wolf, 2010/05/20
- [Qemu-devel] [PATCH 4/8] block: fix sector comparism in multiwrite_req_compare,
Kevin Wolf <=
- [Qemu-devel] [PATCH 3/8] virtio-blk: fix barrier support, Kevin Wolf, 2010/05/20
- [Qemu-devel] [PATCH 1/8] block: fix aio_flush segfaults for read-only protocols (e.g. curl), Kevin Wolf, 2010/05/20
- [Qemu-devel] [PATCH 5/8] block: Make find_image_format() return 'raw' BlockDriver for SG_IO devices, Kevin Wolf, 2010/05/20
- [Qemu-devel] [PATCH 6/8] block: Add SG_IO device check in refresh_total_sectors(), Kevin Wolf, 2010/05/20
- [Qemu-devel] [PATCH 8/8] vvfat: More build fixes with DEBUG, Kevin Wolf, 2010/05/20
- [Qemu-devel] [PATCH 7/8] vvfat: Fix compilation with DEBUG defined, Kevin Wolf, 2010/05/20