NFSv4.1: turn off pNFS on ds connection failure

If a data server is unavailable, go through MDS.

Mark the deviceid containing the data server as a negative cache entry.
Do not try to connect to any data server on a deviceid marked as a negative
cache entry. Mark any layout that tries to use the marked deviceid as failed.

Inodes with a layout marked as fails will not use the layout for I/O, and will
not perform any more layoutgets.
Inodes without a layout will still do layoutget, but the layout will get
marked immediately.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 1f4c153441a1..3e545144a0b2 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -739,15 +739,16 @@ pnfs_update_layout(struct inode *ino,
                 dprintk("%s matches recall, use MDS\n", __func__);
                 goto out_unlock;
         }
-        /* Check to see if the layout for the given range already exists */
-        lseg = pnfs_find_lseg(lo, iomode);
-        if (lseg)
-                goto out_unlock;
 
         /* if LAYOUTGET already failed once we don't try again */
         if (test_bit(lo_fail_bit(iomode), &nfsi->layout->plh_flags))
                 goto out_unlock;
 
+        /* Check to see if the layout for the given range already exists */
+        lseg = pnfs_find_lseg(lo, iomode);
+        if (lseg)
+                goto out_unlock;
+
         if (pnfs_layoutgets_blocked(lo, NULL, 0))
                 goto out_unlock;
         atomic_inc(&lo->plh_outstanding);