[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [RFC V4 24/30] qcow2: Do not overwrite existing entries wit
From: |
Benoît Canet |
Subject: |
[Qemu-devel] [RFC V4 24/30] qcow2: Do not overwrite existing entries with QCOW_OFLAG_COPIED. |
Date: |
Wed, 2 Jan 2013 17:16:27 +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 dbcb6d2..07037a0 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -709,6 +709,10 @@ 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 V4 08/30] qcow2: Implement qcow2_compute_cluster_hash., (continued)
- [Qemu-devel] [RFC V4 08/30] qcow2: Implement qcow2_compute_cluster_hash., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 09/30] qcow2: Extract qcow2_dedup_grow_table, Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 10/30] qcow2: Add qcow2_dedup_grow_table and use it., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 14/30] qcow2-cache: Allow to choose table size at creation., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 15/30] qcow2: Add qcow2_dedup_init and qcow2_dedup_close., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 17/30] block: Add qemu-img dedup create option., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 21/30] qcow2: Add verification of dedup table., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 23/30] qcow2: Add check_dedup_l2 in order to check l2 of dedup table., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 19/30] qcow2: Integrate deduplication in qcow2_co_writev loop., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 25/30] qcow2: Integrate SKEIN hash algorithm in deduplication., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 24/30] qcow2: Do not overwrite existing entries with QCOW_OFLAG_COPIED.,
Benoît Canet <=
- [Qemu-devel] [RFC V4 30/30] qemu-iotests: Filter dedup=on/off so existing tests don't break., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 29/30] qcow2: init and cleanup deduplication., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 20/30] qcow2: Serialize write requests when deduplication is activated., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 22/30] qcow2: Adapt checking of QCOW_OFLAG_COPIED for dedup., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 28/30] qcow: Set dedup cluster block size to 64KB., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 27/30] qcow2: Use large L2 table for deduplication., Benoît Canet, 2013/01/02
- [Qemu-devel] [RFC V4 12/30] qcow2: Load and save deduplication table header extension., Benoît Canet, 2013/01/02