[XFS] Barriers need to be dynamically checked and switched off

If the underlying block device suddenly stops supporting barriers, we need
to handle the -EOPNOTSUPP error in a sane manner rather than shutting
down the filesystem. If we get this error, clear the barrier flag, reissue
the I/O, and tell the world bad things are occurring.

SGI-PV: 964544
SGI-Modid: xfs-linux-melb:xfs-kern:28568a

Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Tim Shimmin <tes@sgi.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index b0f0e58866de..8d9298c99763 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -997,7 +997,18 @@ xfs_buf_iodone_work(
         xfs_buf_t               *bp =
                 container_of(work, xfs_buf_t, b_iodone_work);
 
-        if (bp->b_iodone)
+        /*
+         * We can get an EOPNOTSUPP to ordered writes.  Here we clear the
+         * ordered flag and reissue them.  Because we can't tell the higher
+         * layers directly that they should not issue ordered I/O anymore, they
+         * need to check if the ordered flag was cleared during I/O completion.
+         */
+        if ((bp->b_error == EOPNOTSUPP) &&
+            (bp->b_flags & (XBF_ORDERED|XBF_ASYNC)) == (XBF_ORDERED|XBF_ASYNC)) {
+                XB_TRACE(bp, "ordered_retry", bp->b_iodone);
+                bp->b_flags &= ~XBF_ORDERED;
+                xfs_buf_iorequest(bp);
+        } else if (bp->b_iodone)
                 (*(bp->b_iodone))(bp);
         else if (bp->b_flags & XBF_ASYNC)
                 xfs_buf_relse(bp);