[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>

3 files changed, 25 insertions, 9 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);
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 491d1f4f202d..17ad5e463710 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -304,14 +304,6 @@ xfs_mountfs_check_barriers(xfs_mount_t *mp)
                 return;
         }
 
-        if (mp->m_ddev_targp->bt_bdev->bd_disk->queue->ordered ==
-                                        QUEUE_ORDERED_NONE) {
-                xfs_fs_cmn_err(CE_NOTE, mp,
-                  "Disabling barriers, not supported by the underlying device");
-                mp->m_flags &= ~XFS_MOUNT_BARRIER;
-                return;
-        }
-
         if (xfs_readonly_buftarg(mp->m_ddev_targp)) {
                 xfs_fs_cmn_err(CE_NOTE, mp,
                   "Disabling barriers, underlying device is readonly");
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 9bfb69e1e885..db09e1ea5cf3 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -949,6 +949,19 @@ xlog_iodone(xfs_buf_t *bp)
         l = iclog->ic_log;
 
         /*
+         * If the ordered flag has been removed by a lower
+         * layer, it means the underlyin device no longer supports
+         * barrier I/O. Warn loudly and turn off barriers.
+         */
+        if ((l->l_mp->m_flags & XFS_MOUNT_BARRIER) && !XFS_BUF_ORDERED(bp)) {
+                l->l_mp->m_flags &= ~XFS_MOUNT_BARRIER;
+                xfs_fs_cmn_err(CE_WARN, l->l_mp,
+                                "xlog_iodone: Barriers are no longer supported"
+                                " by device. Disabling barriers\n");
+                xfs_buftrace("XLOG_IODONE BARRIERS OFF", bp);
+        }
+
+        /*
          * Race to shutdown the filesystem if we see an error.
          */
         if (XFS_TEST_ERROR((XFS_BUF_GETERROR(bp)), l->l_mp,