Re: [PATCH] pNFS/flexfiles: ff_layout_pg_init_read should exit on error

["Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>]

Hi Trond,

shouldn't this go to stable as well?

Tigran.

----- Original Message -----
> From: "Trond Myklebust" <trondmy@gmail.com>
> To: "Anna Schumaker" <Anna.Schumaker@netapp.com>
> Cc: "linux-nfs" <linux-nfs@vger.kernel.org>
> Sent: Friday, August 17, 2018 4:31:08 PM
> Subject: [PATCH] pNFS/flexfiles: ff_layout_pg_init_read should exit on error

> From: Trond Myklebust <trond.myklebust@primarydata.com>
> 
> If we get an error while retrieving the layout, then we should
> report it rather than falling back to I/O through the MDS.
> 
> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
> ---
> fs/nfs/flexfilelayout/flexfilelayout.c | 28 ++++++++++----------------
> 1 file changed, 11 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c
> b/fs/nfs/flexfilelayout/flexfilelayout.c
> index 280b6b060d53..cae43333ef16 100644
> --- a/fs/nfs/flexfilelayout/flexfilelayout.c
> +++ b/fs/nfs/flexfilelayout/flexfilelayout.c
> @@ -812,7 +812,6 @@ ff_layout_pg_get_read(struct nfs_pageio_descriptor *pgio,
> 		      struct nfs_page *req,
> 		      bool strict_iomode)
> {
> -retry_strict:
> 	pnfs_put_lseg(pgio->pg_lseg);
> 	pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
> 					   req->wb_context,
> @@ -825,16 +824,6 @@ ff_layout_pg_get_read(struct nfs_pageio_descriptor *pgio,
> 		pgio->pg_error = PTR_ERR(pgio->pg_lseg);
> 		pgio->pg_lseg = NULL;
> 	}
> -
> -	/* If we don't have checking, do get a IOMODE_RW
> -	 * segment, and the server wants to avoid READs
> -	 * there, then retry!
> -	 */
> -	if (pgio->pg_lseg && !strict_iomode &&
> -	    ff_layout_avoid_read_on_rw(pgio->pg_lseg)) {
> -		strict_iomode = true;
> -		goto retry_strict;
> -	}
> }
> 
> static void
> @@ -849,14 +838,16 @@ ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
> retry:
> 	pnfs_generic_pg_check_layout(pgio);
> 	/* Use full layout for now */
> -	if (!pgio->pg_lseg)
> +	if (!pgio->pg_lseg) {
> 		ff_layout_pg_get_read(pgio, req, false);
> -	else if (ff_layout_avoid_read_on_rw(pgio->pg_lseg))
> +		if (!pgio->pg_lseg)
> +			goto out_nolseg;
> +	}
> +	if (ff_layout_avoid_read_on_rw(pgio->pg_lseg)) {
> 		ff_layout_pg_get_read(pgio, req, true);
> -
> -	/* If no lseg, fall back to read through mds */
> -	if (pgio->pg_lseg == NULL)
> -		goto out_mds;
> +		if (!pgio->pg_lseg)
> +			goto out_nolseg;
> +	}
> 
> 	ds = ff_layout_choose_best_ds_for_read(pgio->pg_lseg, 0, &ds_idx);
> 	if (!ds) {
> @@ -878,6 +869,9 @@ ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
> 	pgm->pg_bsize = mirror->mirror_ds->ds_versions[0].rsize;
> 
> 	return;
> +out_nolseg:
> +	if (pgio->pg_error < 0)
> +		return;
> out_mds:
> 	pnfs_put_lseg(pgio->pg_lseg);
> 	pgio->pg_lseg = NULL;
> --
> 2.17.1