Re: [PATCH 1/4] pNFS: Fix post-layoutget error handling in pnfs_update_layout()

[Jeff Layton <jlayton@redhat.com>]

On Thu, 2016-07-14 at 18:58 -0400, Trond Myklebust wrote:
> The non-retry error path is currently broken and ends up releasing the
> reference to the layout twice. It also can end up clearing the
> NFS_LAYOUT_FIRST_LAYOUTGET flag twice, causing a race.
> 
> In addition, the retry path will fail to decrement the plh_outstanding
> counter.
> 
> Fixes: 183d9e7b112aa ("pnfs: rework LAYOUTGET retry handling")
> Cc: stable@vger.kernel.org # 4.7
> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
> ---
>  fs/nfs/pnfs.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 0fbe734cc38c..73b0dc90265a 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -1645,6 +1645,7 @@ lookup_again:
>  	lseg = send_layoutget(lo, ctx, &stateid, &arg, &timeout, gfp_flags);
>  	trace_pnfs_update_layout(ino, pos, count, iomode, lo, lseg,
>  				 PNFS_UPDATE_LAYOUT_SEND_LAYOUTGET);
> +	atomic_dec(&lo->plh_outstanding);
>  	if (IS_ERR(lseg)) {
>  		switch(PTR_ERR(lseg)) {
>  		case -ERECALLCONFLICT:
> @@ -1652,26 +1653,25 @@ lookup_again:
>  				lseg = NULL;
>  			/* Fallthrough */
>  		case -EAGAIN:
> -			pnfs_put_layout_hdr(lo);
> -			if (first)
> -				pnfs_clear_first_layoutget(lo);
> -			if (lseg) {
> -				trace_pnfs_update_layout(ino, pos, count,
> -					iomode, lo, lseg, PNFS_UPDATE_LAYOUT_RETRY);
> -				goto lookup_again;
> -			}
> -			/* Fallthrough */
> +			break;
>  		default:
>  			if (!nfs_error_is_fatal(PTR_ERR(lseg))) {
>  				pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
>  				lseg = NULL;
>  			}
>  		}
> +		if (lseg) {
> +			pnfs_put_layout_hdr(lo);
> +			if (first)
> +				pnfs_clear_first_layoutget(lo);
> +			trace_pnfs_update_layout(ino, pos, count,
> +				iomode, lo, lseg, PNFS_UPDATE_LAYOUT_RETRY);
> +			goto lookup_again;
> +		}
>  	} else {
>  		pnfs_layout_clear_fail_bit(lo, pnfs_iomode_to_fail_bit(iomode));
>  	}
>  
> -	atomic_dec(&lo->plh_outstanding);
>  out_put_layout_hdr:
>  	if (first)
>  		pnfs_clear_first_layoutget(lo);

The whole set looks good to me. Nice catches all around!

Reviewed-by: Jeff Layton <jlayton@redhat.com>