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

[Jan Kara]

On Wed 19-02-14 14:11:02, Jan Kara wrote:
> 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.
  Hum, so this likely isn't the whole story because I can still see the
corruption. At least I've now found the metadata cache and basically
understand how it works so I'm now reading code around that and trying to
understand what screws up quota code...

								Honza

> 
> 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
> 
-- 
Jan Kara <jack at suse.cz>
SUSE Labs, CR