Re: [PATCH] writeback: Fix data corruption on NFS

[Fengguang Wu <fengguang.wu@intel.com>]

On Wed, Dec 11, 2013 at 08:59:36PM +0100, Jan Kara wrote:
> Commit 4f8ad655dbc8 "writeback: Refactor writeback_single_inode()" added
> a condition to skip clean inode. However this is wrong in WB_SYNC_ALL
> mode because there we also want to wait for outstanding writeback on
> possibly clean inode. This was causing occasional data corruption issues
> on NFS because it uses sync_inode() to make sure all outstanding writes
> are flushed to the server before truncating the inode and with
> sync_inode() returning prematurely file was sometimes extended back
> by an outstanding write after it was truncated.
> 
> So modify the test to also check for pages under writeback in
> WB_SYNC_ALL mode.

Applied to the writeback tree. Thank you, Jan!

Regards,
Fengguang

> CC: stable@vger.kernel.org # >= 3.5
> Fixes: 4f8ad655dbc82cf05d2edc11e66b78a42d38bf93
> Reported-and-tested-by: Dan Duval <dan.duval@oracle.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/fs-writeback.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
>  Fenguang, can you please merge this patch? Thanks!
> 
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 1f4a10ece2f1..e0259a163f98 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -516,13 +516,16 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
>  	}
>  	WARN_ON(inode->i_state & I_SYNC);
>  	/*
> -	 * Skip inode if it is clean. We don't want to mess with writeback
> -	 * lists in this function since flusher thread may be doing for example
> -	 * sync in parallel and if we move the inode, it could get skipped. So
> -	 * here we make sure inode is on some writeback list and leave it there
> -	 * unless we have completely cleaned the inode.
> +	 * Skip inode if it is clean and we have no outstanding writeback in
> +	 * WB_SYNC_ALL mode. We don't want to mess with writeback lists in this
> +	 * function since flusher thread may be doing for example sync in
> +	 * parallel and if we move the inode, it could get skipped. So here we
> +	 * make sure inode is on some writeback list and leave it there unless
> +	 * we have completely cleaned the inode.
>  	 */
> -	if (!(inode->i_state & I_DIRTY))
> +	if (!(inode->i_state & I_DIRTY) &&
> +	    (wbc->sync_mode != WB_SYNC_ALL ||
> +	     !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_WRITEBACK)))
>  		goto out;
>  	inode->i_state |= I_SYNC;
>  	spin_unlock(&inode->i_lock);
> -- 
> 1.8.1.4