xfs
[Top] [All Lists]

Re: [PATCH 1/8] xfs: check for buffer errors before waiting

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 1/8] xfs: check for buffer errors before waiting
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Thu, 29 Mar 2012 16:48:11 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120329211025.GD692@dastard>
References: <1333023835-12856-1-git-send-email-david@xxxxxxxxxxxxx> <1333023835-12856-2-git-send-email-david@xxxxxxxxxxxxx> <4F74B229.6030707@xxxxxxx> <20120329211025.GD692@dastard>
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0
On 03/29/12 16:10, Dave Chinner wrote:
On Thu, Mar 29, 2012 at 02:04:09PM -0500, Mark Tinguely wrote:
On 03/29/12 07:23, Dave Chinner wrote:
From: Dave Chinner<dchinner@xxxxxxxxxx>

If we call xfs_buf_iowait() on a buffer that failed dispatch due to
an IO error, it will wait forever for an Io that does not exist.
This is hndled in xfs_buf_read, but there is other code that calls
xfs_buf_iowait directly that doesn't.

Rather than make the call sites have to handle checking for dispatch
errors and then checking for completion errors, make
xfs_buf_iowait() check for dispatch errors on the buffer before
waiting. This means we handle both dispatch and completion errors
with one set of error handling at the caller sites.

Signed-off-by: Dave Chinner<dchinner@xxxxxxxxxx>
---

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 396e3bf..64ed6ff 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -179,6 +179,7 @@ xlog_bread_noalign(
        XFS_BUF_SET_ADDR(bp, log->l_logBBstart + blk_no);
        XFS_BUF_READ(bp);
        XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
+       bp->b_error = 0;

        xfsbdstrat(log->l_mp, bp);
        error = xfs_buf_iowait(bp);
@@ -266,6 +267,7 @@ xlog_bwrite(
        xfs_buf_hold(bp);
        xfs_buf_lock(bp);
        XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
+       bp->b_error = 0;

        error = xfs_bwrite(bp);
        if (error)

Just curious, were these needed for a particular reason?

If the previous user of the buffer got an error, it is not
guaranteed to be cleared because the buffer is not re-initialised.
i.e. it's an uncached buffer that we control completely and reuse
from IO to IO with just a reset of the bno and length. If b_error is
non zero here, then the IO can fail because nothing else clears the
error in the dispatch path....

Cheers,

Dave.

Thank-you for the explanation.

FYI: I am having problems with the patches applying. This patch complained at hunk at offset 623. Maybe I am using too new of kernel source.

--Mark.

<Prev in Thread] Current Thread [Next in Thread>