[gentoo-commits] gentoo-x86 commit in app-emulation/qemu-kvm/files: qemu-kvm-0.12.4-large-virtio-corruption.patch

[gentoo-commits] gentoo-x86 commit in app-emulation/qemu-kvm/files: qemu-kvm-0.12.4-large-virtio-corruption.patch

[Doug Goldstein (cardoe)]

cardoe      10/06/15 18:41:41

  Added:                qemu-kvm-0.12.4-large-virtio-corruption.patch
  Log:
  Fix issue with large virtio disks getting corrupted. bug #321005
  (Portage version: 2.1.8.3/cvs/Linux x86_64)

Revision  Changes    Path
1.1                  app-emulation/qemu-kvm/files/qemu-kvm-0.12.4-large-virtio-corruption.patch

file : http://sources.gentoo.org/viewvc.cgi/gentoo-x86/app-emulation/qemu-kvm/files/qemu-kvm-0.12.4-large-virtio-corruption.patch?rev=1.1&view=markup
plain: http://sources.gentoo.org/viewvc.cgi/gentoo-x86/app-emulation/qemu-kvm/files/qemu-kvm-0.12.4-large-virtio-corruption.patch?rev=1.1&content-type=text/plain

Index: qemu-kvm-0.12.4-large-virtio-corruption.patch
===================================================================
From: Christoph Hellwig <hch@lst.de>

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 <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 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;
+    }
 }
 
 /*