[Ocfs2-devel] [PATCH] ocfs2: Fix quota file corruption

[Jan Kara]

Global quota files are accessed from different nodes and reading and
writing of these files happens via block device page cache. Thus even
though the access between nodes is properly serialized by quota file's
inode lock we cannot rely on consistency of block device page cache
between nodes. Indeed currently it is possible to corrupt quota files by
creating and deleting quota structures from two nodes in parallel. Fix
the problem by using OCFS2_BH_IGNORE_CACHE mount option when reading
from quota file.

CC: Goldwyn Rodrigues <rgoldwyn at suse.de>
CC: Mark Fasheh <mfasheh at suse.de>
Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/ocfs2/quota_global.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

  This is a quick fix for quota file corruption I have found during my testing
(to be used for 3.13 and -stable kernels). Longer term we likely want to do
something more clever. Ideally we would invalidate relevant blocks from buffer
cache when node releases quota file's inode lock (similarly as we do it for
page cache). I wanted to do it similarly as for e.g. extent tree blocks but
I failed to find how consistency of those between nodes is achieved. Can
anyone point me in the right direction? Thanks in advance.

diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c
index aaa50611ec66..f1f0cca15db6 100644
--- a/fs/ocfs2/quota_global.c
+++ b/fs/ocfs2/quota_global.c
@@ -151,7 +151,8 @@ int ocfs2_read_quota_phys_block(struct inode *inode, u64 p_block,
 	int rc;
 
 	*bhp = NULL;
-	rc = ocfs2_read_blocks(INODE_CACHE(inode), p_block, 1, bhp, 0,
+	rc = ocfs2_read_blocks(INODE_CACHE(inode), p_block, 1, bhp,
+			       OCFS2_BH_IGNORE_CACHE,
 			       ocfs2_validate_quota_block);
 	if (rc)
 		mlog_errno(rc);
-- 
1.8.1.4