[linux-cifs-client] [PATCH] cifs: Detect errors in cifs_writepages when called during background write-back

[Peter Schwenke]

Peter Schwenke wrote:
> The return code isn't checked in the case of cifs_writepages being
> invoked as a result of pdflush and potentially other background
> write-back. This results in data integrity problems when errors such as
> a network break occur when CIFSSMBWrite2 is called.  The resulting error
> isn't acted on.  This patch hangs on to the write-behind error so that it
> is available for detection later on.
> 
> Signed-off-by: Peter Schwenke <peter at bluetoad.com.au>
> ---
>  fs/cifs/file.c |   15 ++++++++++++++-
>  1 files changed, 14 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 042b122..f1a5b1e 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -1200,6 +1200,7 @@ static int cifs_writepages(struct address_space *mapping,
>  	unsigned int bytes_to_write;
>  	unsigned int bytes_written;
>  	struct cifs_sb_info *cifs_sb;
> +	struct cifsInodeInfo *cifs_inode = CIFS_I(mapping->host);
>  	int done = 0;
>  	pgoff_t end;
>  	pgoff_t index;
> @@ -1354,7 +1355,7 @@ retry:
>  			 * CIFSSMBWrite2.  We can't rely on the last handle
>  			 * we used to still be valid
>  			 */
> -			open_file = find_writable_file(CIFS_I(mapping->host));
> +			open_file = find_writable_file(cifs_inode);
>  			if (!open_file) {
>  				cERROR(1, ("No writable handles for inode"));
>  				rc = -EBADF;
> @@ -1374,6 +1375,18 @@ retry:
>  						set_bit(AS_ENOSPC, &mapping->flags);
>  					else
>  						set_bit(AS_EIO, &mapping->flags);
> +					/*
> +					 * The return code isn't checked in the
> +					 * case of cifs_writepages being
> +					 * invoked from background write outs
> +					 * i.e. generic_sync_sb_inodes()
> +					 */
> +					if (wbc->sync_mode == WB_SYNC_NONE) {
> +						if (rc == -ENOSPC)
> +							cifs_inode->write_behind_rc =  rc;
> +						else
> +							cifs_inode->write_behind_rc =  -EIO;
> +					}
>  				} else {
>  					cifs_stats_bytes_written(cifs_sb->tcon,
>  								 bytes_written);

I was wondering if this patch was the correct way of fixing the problem.
   This was against 2.6.27

-- 
                                                              Regards
                                                              ...Peter