pNFS: Don't forget the layout stateid if there are outstanding LAYOUTGETs

If there are outstanding LAYOUTGET rpc calls, then we want to ensure that
we keep the layout stateid around so we that don't inadvertently pick up
an old/misordered sequence id.
The race is as follows:

Client				Server
======				======
LAYOUTGET(seqid)
LAYOUTGET(seqid)
				return LAYOUTGET(seqid+1)
				return LAYOUTGET(seqid+2)
process LAYOUTGET(seqid+2)
	forget layout
process LAYOUTGET(seqid+1)

If it forgets the layout stateid before processing seqid+1, then
the client will not check the layout->plh_barrier, and so will set
the stateid with seqid+1.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index cd8b5fca33f6e2740d048fcaf055dde0cd3146ee..2c93a85eda51c9d6ebcde892d1e7ca60a1f159b3 100644 (file)
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -365,7 +365,8 @@ pnfs_layout_remove_lseg(struct pnfs_layout_hdr *lo,
        /* Matched by pnfs_get_layout_hdr in pnfs_layout_insert_lseg */
        atomic_dec(&lo->plh_refcount);
        if (list_empty(&lo->plh_segs)) {
-               set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
+               if (atomic_read(&lo->plh_outstanding) == 0)
+                       set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
                clear_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags);
        }
        rpc_wake_up(&NFS_SERVER(inode)->roc_rpcwaitq);