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authorMark Fasheh <mfasheh@suse.com>2011-06-23 01:23:38 +0400
committerJoel Becker <jlbec@evilplan.org>2011-07-28 13:07:16 +0400
commita11f7e63c59810a81494d4c4b028af707d4c7ca4 (patch)
tree6d28cfc9519f96db5c20780bf765de9e0fc03bef /fs/ocfs2/inode.h
parent730e663bd82c1a10a85ff00728d34152a5a67ec8 (diff)
downloadlinux-a11f7e63c59810a81494d4c4b028af707d4c7ca4.tar.xz
ocfs2: serialize unaligned aio
Fix a corruption that can happen when we have (two or more) outstanding aio's to an overlapping unaligned region. Ext4 (e9e3bcecf44c04b9e6b505fd8e2eb9cea58fb94d) and xfs recently had to fix similar issues. In our case what happens is that we can have an outstanding aio on a region and if a write comes in with some bytes overlapping the original aio we may decide to read that region into a page before continuing (typically because of buffered-io fallback). Since we have no ordering guarantees with the aio, we can read stale or bad data into the page and then write it back out. If the i/o is page and block aligned, then we avoid this issue as there won't be any need to read data from disk. I took the same approach as Eric in the ext4 patch and introduced some serialization of unaligned async direct i/o. I don't expect this to have an effect on the most common cases of AIO. Unaligned aio will be slower though, but that's far more acceptable than data corruption. Signed-off-by: Mark Fasheh <mfasheh@suse.com> Signed-off-by: Joel Becker <jlbec@evilplan.org>
Diffstat (limited to 'fs/ocfs2/inode.h')
-rw-r--r--fs/ocfs2/inode.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/ocfs2/inode.h b/fs/ocfs2/inode.h
index 1c508b149b3a..88924a3133fa 100644
--- a/fs/ocfs2/inode.h
+++ b/fs/ocfs2/inode.h
@@ -43,6 +43,9 @@ struct ocfs2_inode_info
/* protects extended attribute changes on this inode */
struct rw_semaphore ip_xattr_sem;
+ /* Number of outstanding AIO's which are not page aligned */
+ atomic_t ip_unaligned_aio;
+
/* These fields are protected by ip_lock */
spinlock_t ip_lock;
u32 ip_open_count;