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[PATCH 1/2] xfs: don't block on buffer read errors

To: xfs@xxxxxxxxxxx
Subject: [PATCH 1/2] xfs: don't block on buffer read errors
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 13 Jul 2010 17:50:49 +1000
Cc: linux-kernel@xxxxxxxxxxxxxxx, axboe@xxxxxxxxx
In-reply-to: <1279007450-10457-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1279007450-10457-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

xfs_buf_read() fails to detect dispatch errors before attempting to
wait on sychronous IO. If there was an error, it will get stuck
forever, waiting for an I/O that was never started. Make sure the
error is detected correctly.

Further, such a failure can leave locked pages in the page cache
which will cause a later operation to hang on the page. Ensure that
we correctly process pages in the buffers when we get a dispatch
error.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/xfs/linux-2.6/xfs_buf.c |   15 +++++++++++++--
 1 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 76bb13c..ec79634 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -578,7 +578,7 @@ _xfs_buf_read(
                        XBF_READ_AHEAD | _XBF_RUN_QUEUES);
 
        status = xfs_buf_iorequest(bp);
-       if (!status && !(flags & XBF_ASYNC))
+       if (!(status || XFS_BUF_ISERROR(bp) || (flags & XBF_ASYNC)))
                status = xfs_buf_iowait(bp);
        return status;
 }
@@ -1280,8 +1280,19 @@ submit_io:
                if (size)
                        goto next_chunk;
        } else {
-               bio_put(bio);
+               /*
+                * if we get here, no pages were added to the bio. However,
+                * we can't just error out here - if the pages are locked then
+                * we have to unlock them otherwise we can hang on a later
+                * access to the page.
+                */
                xfs_buf_ioerror(bp, EIO);
+               if (bp->b_flags & _XBF_PAGE_LOCKED) {
+                       int i;
+                       for (i = 0; i < bp->b_page_count; i++)
+                               unlock_page(bp->b_pages[i]);
+               }
+               bio_put(bio);
        }
 }
 
-- 
1.7.1

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