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[Qemu-devel] [RFC V3 22/24] qcow2: Do not overwrite existing entries wit
From: |
Benoît Canet |
Subject: |
[Qemu-devel] [RFC V3 22/24] qcow2: Do not overwrite existing entries with QCOW_OFLAG_COPIED. |
Date: |
Mon, 26 Nov 2012 14:05:21 +0100 |
In the case of a race condition between two writes a l2 entry can be written
without QCOW_OFLAG_COPIED before the first write fill it.
This patch simply check if the l2 entry has the correct offset without
QCOW_OFLAG_COPIED and do nothing.
Signed-off-by: Benoit Canet <address@hidden>
---
block/qcow2-cluster.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 8db1b2a..0042742 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -699,6 +699,10 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs,
QCowL2Meta *m)
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
for (i = 0; i < m->nb_clusters; i++) {
+ if (be64_to_cpu(l2_table[l2_index + i]) ==
+ (cluster_offset + (i << s->cluster_bits))) {
+ continue;
+ }
/* if two concurrent writes happen to the same unallocated cluster
* each write allocates separate cluster and writes data concurrently.
* The first one to complete updates l2 table with pointer to its
--
1.7.10.4
- [Qemu-devel] [RFC V3 09/24] qcow2: Extract qcow2_dedup_grow_table, (continued)
- [Qemu-devel] [RFC V3 09/24] qcow2: Extract qcow2_dedup_grow_table, Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 13/24] qcow2: Add qcow2_dedup_init and qcow2_dedup_close., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 12/24] qcow2: Extract qcow2_do_table_init., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 11/24] qcow2: Load and save deduplication table header extension., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 14/24] qcow2: Extract qcow2_add_feature and qcow2_remove_feature., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 16/24] qcow2: Allow creation of images using deduplication., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 17/24] qcow2: Behave correctly when refcount reach 0 or 2^16., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 19/24] qcow2: Add verification of dedup table., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 24/24] qemu-iotests: Filter dedup=on/off so existing tests don't break., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 20/24] qcow2: Adapt checking of QCOW_OFLAG_COPIED for dedup., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 22/24] qcow2: Do not overwrite existing entries with QCOW_OFLAG_COPIED.,
Benoît Canet <=
- [Qemu-devel] [RFC V3 07/24] qcow2: Add qcow2_dedup_write_new_hashes., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 18/24] qcow2: Integrate deduplication in qcow2_co_writev loop., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 08/24] qcow2: Implement qcow2_compute_cluster_hash., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 21/24] qcow2: Add check_dedup_l2 in order to check l2 of dedup table., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 23/24] qcow2: init and cleanup deduplication., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 10/24] qcow2: create function to load deduplication hashes at startup., Benoît Canet, 2012/11/26
- [Qemu-devel] [RFC V3 15/24] block: Add dedup image create option., Benoît Canet, 2012/11/26