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[Qemu-devel] [PATCH 43/60] qcow2: Fix avail_sectors in cluster allocatio
From: |
Michael Tokarev |
Subject: |
[Qemu-devel] [PATCH 43/60] qcow2: Fix avail_sectors in cluster allocation code |
Date: |
Mon, 4 Feb 2013 14:40:53 +0400 |
From: Kevin Wolf <address@hidden>
avail_sectors should really be the number of sectors from the start of
the allocation, not from the start of the write request.
We're lucky enough that this mistake didn't cause any real bug.
avail_sectors is only used in the intialiser of QCowL2Meta:
.nb_available = MIN(requested_sectors, avail_sectors),
m->nb_available in turn is only used for COW at the end of the
allocation. A COW occurs only if the request wasn't cluster aligned,
which in turn would imply that requested_sectors was less than
avail_sectors (both in the original and in the fixed version). In this
case avail_sectors is ignored and therefore the mistake doesn't cause
any misbehaviour.
Signed-off-by: Kevin Wolf <address@hidden>
(cherry picked from commit b7ab0fea37c15ca9e249c42c46f5c48fd1a0943c)
Signed-off-by: Michael Tokarev <address@hidden>
---
block/qcow2-cluster.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index c173fcd..58e7e24 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -949,8 +949,16 @@ again:
/* save info needed for meta data update */
if (nb_clusters > 0) {
+ /*
+ * requested_sectors: Number of sectors from the start of the first
+ * newly allocated cluster to the end of the (possibly shortened
+ * before) write request.
+ *
+ * avail_sectors: Number of sectors from the start of the first
+ * newly allocated to the end of the last newly allocated cluster.
+ */
int requested_sectors = n_end - keep_clusters * s->cluster_sectors;
- int avail_sectors = (keep_clusters + nb_clusters)
+ int avail_sectors = nb_clusters
<< (s->cluster_bits - BDRV_SECTOR_BITS);
*m = (QCowL2Meta) {
--
1.7.10.4
- [Qemu-devel] [PATCH 25/60] hw: Fix return value check for bdrv_read, bdrv_write, (continued)
- [Qemu-devel] [PATCH 25/60] hw: Fix return value check for bdrv_read, bdrv_write, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 58/60] qxl: save qemu_create_displaysurface_from result, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 50/60] slirp: Don't crash on packets from 0.0.0.0/8., Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 27/60] x86: Fixed incorrect segment base address addition in 64-bits mode, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 49/60] tap: reset vnet header size on open, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 18/60] e1000: flush queue whenever can_receive can go from false to true, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 19/60] fix entry pointer for ELF kernels loaded with -kernel option, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 31/60] linux-user: fix emulation of getdents, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 12/60] intel_hda: do not call msi_reset when only device state needs resetting, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 44/60] qcow2: Fix refcount table size calculation, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 43/60] qcow2: Fix avail_sectors in cluster allocation code,
Michael Tokarev <=
- [Qemu-devel] [PATCH 13/60] usb-audio: fix usb version, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 14/60] fpu/softfloat.c: Return correctly signed values from uint64_to_float32, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 40/60] nbd: fixes to read-only handling, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 60/60] migration: Fix madvise breakage if host and guest have different page sizes, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 39/60] m68k: Return semihosting errno values correctly, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 28/60] Fixes related to processing of qemu's -numa option, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 09/60] ahci: properly reset PxCMD on HBA reset, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 51/60] vmdk: Fix data corruption bug in WRITE and READ handling, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 59/60] target-xtensa: fix ITLB/DTLB page protection flags, Michael Tokarev, 2013/02/04
- [Qemu-devel] [PATCH 55/60] arm_boot: Change initrd load address to "halfway through RAM", Michael Tokarev, 2013/02/04