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[Qemu-devel] [PATCH 11/11] qcow2: Fix order in L2 table COW
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 11/11] qcow2: Fix order in L2 table COW |
Date: |
Thu, 10 Feb 2011 16:51:26 +0100 |
When copying L2 tables (this happens only with internal snapshots), the order
wasn't completely safe, so that after a crash you could end up with a L2 table
that has too low refcount, possibly leading to corruption in the long run.
This patch puts the operations in the right order: First allocate the new
L2 table and replace the reference, and only then decrease the refcount of the
old table.
Signed-off-by: Kevin Wolf <address@hidden>
---
block/qcow2-cluster.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 437aaa8..750abe3 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -515,13 +515,16 @@ static int get_cluster_table(BlockDriverState *bs,
uint64_t offset,
return ret;
}
} else {
- /* FIXME Order */
- if (l2_offset)
- qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));
+ /* First allocate a new L2 table (and do COW if needed) */
ret = l2_allocate(bs, l1_index, &l2_table);
if (ret < 0) {
return ret;
}
+
+ /* Then decrease the refcount of the old table */
+ if (l2_offset) {
+ qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));
+ }
l2_offset = s->l1_table[l1_index] & ~QCOW_OFLAG_COPIED;
}
--
1.7.2.3
- [Qemu-devel] [PATCH 03/11] qcow2: Fix error handling for immediate backing file read failure, (continued)
- [Qemu-devel] [PATCH 03/11] qcow2: Fix error handling for immediate backing file read failure, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 02/11] QCOW2: bug fix - read base image beyond its size, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 01/11] Change snapshot_blkdev hmp to use correct argument type for device, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 05/11] qerror: Add QERR_UNKNOWN_BLOCK_FORMAT_FEATURE, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 06/11] qcow2: Report error for version > 2, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 04/11] qcow2: Fix error handling for reading compressed clusters, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 08/11] qemu-img: Improve error messages for failed bdrv_open, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 09/11] blockdev: Plug memory leak in drive_uninit(), Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 10/11] blockdev: Plug memory leak in drive_init() error paths, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 07/11] qed: Report error for unsupported features, Kevin Wolf, 2011/02/10
- [Qemu-devel] [PATCH 11/11] qcow2: Fix order in L2 table COW,
Kevin Wolf <=
- Re: [Qemu-devel] [PULL 00/11] Block patches for master, Anthony Liguori, 2011/02/14