From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ipmail07.adl2.internode.on.net ([150.101.137.131]:23750 "EHLO ipmail07.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726894AbeK1QJP (ORCPT ); Wed, 28 Nov 2018 11:09:15 -0500 Date: Wed, 28 Nov 2018 16:08:50 +1100 From: Dave Chinner To: Allison Henderson Cc: linux-block@vger.kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, martin.petersen@oracle.com, shirley.ma@oracle.com, bob.liu@oracle.com Subject: Re: [PATCH v1 5/7] xfs: Add device retry Message-ID: <20181128050850.GJ6311@dastard> References: <1543376991-5764-1-git-send-email-allison.henderson@oracle.com> <1543376991-5764-6-git-send-email-allison.henderson@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1543376991-5764-6-git-send-email-allison.henderson@oracle.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Nov 27, 2018 at 08:49:49PM -0700, Allison Henderson wrote: > Check to see if the _xfs_buf_read fails. If so loop over the > available mirrors and retry the read > > Signed-off-by: Allison Henderson > --- > fs/xfs/xfs_buf.c | 28 +++++++++++++++++++++++++++- > 1 file changed, 27 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c > index dd8ba59..f102d01 100644 > --- a/fs/xfs/xfs_buf.c > +++ b/fs/xfs/xfs_buf.c > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > > #include "xfs_format.h" > #include "xfs_log_format.h" > @@ -808,6 +809,8 @@ xfs_buf_read_map( > const struct xfs_buf_ops *ops) > { > struct xfs_buf *bp; > + struct request_queue *q; > + unsigned short i; > > flags |= XBF_READ; > > @@ -820,7 +823,30 @@ xfs_buf_read_map( > if (!(bp->b_flags & XBF_DONE)) { > XFS_STATS_INC(target->bt_mount, xb_get_read); > bp->b_ops = ops; > - _xfs_buf_read(bp, flags); > + q = bdev_get_queue(bp->b_target->bt_bdev); > + > + /* > + * Mirrors are indexed 1 - n, specified through the rw_hint. > + * Setting the hint to 0 is unspecified and allows the block > + * layer to decide. > + */ > + for (i = 0; i <= blk_queue_get_mirrors(q); i++) { > + bp->b_error = 0; > + bp->b_rw_hint = i; > + _xfs_buf_read(bp, flags); So the first time through this loop the block layer devices what device to read from, then we iterate devices 1..n on error. Whihc means if device 0 is the only one with good information in it, we may not ever actually read from it. I'd suggest that a hint of "-1" (or equivalent max value) should be used for "device selects mirror leg" rather than 0, so we can actually read from the first device on command. i.e. bp->b_error = 0; bp->b_rw_hint = -1; _xfs_buf_read(bp, flags); if (!bp->b_error) return bp; /* manual iteration to find a good copy */ for (i = 0; i <= blk_queue_get_mirrors(q); i++) { bp->b_error = 0; bp->b_rw_hint = i; _xfs_buf_read(bp, flags); ...... > + > + switch (bp->b_error) { > + case -EIO: > + case -EFSCORRUPTED: > + case -EFSBADCRC: > + /* loop again */ > + continue; > + default: > + goto retry_done; Just return bp here, don't need a jump label for it. Cheers, Dave. -- Dave Chinner david@fromorbit.com