releases/4.4.44/pnfs-fix-race-in-pnfs_wait_on_layoutreturn.patch

From ee284e35d8c71bf5d4d807eaff6f67a17134b359 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@primarydata.com>
Date: Fri, 18 Nov 2016 15:21:30 -0500
Subject: pNFS: Fix race in pnfs_wait_on_layoutreturn

From: Trond Myklebust <trond.myklebust@primarydata.com>

commit ee284e35d8c71bf5d4d807eaff6f67a17134b359 upstream.

We must put the task to sleep while holding the inode->i_lock in order
to ensure atomicity with the test for NFS_LAYOUT_RETURN.

Fixes: 500d701f336b ("NFS41: make close wait for layoutreturn")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/nfs/pnfs.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1185,13 +1185,11 @@ bool pnfs_wait_on_layoutreturn(struct in
 	 * i_lock */
         spin_lock(&ino->i_lock);
         lo = nfsi->layout;
-        if (lo && test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags))
+        if (lo && test_bit(NFS_LAYOUT_RETURN, &lo->plh_flags)) {
+                rpc_sleep_on(&NFS_SERVER(ino)->roc_rpcwaitq, task, NULL);
                 sleep = true;
+	}
         spin_unlock(&ino->i_lock);
-
-        if (sleep)
-                rpc_sleep_on(&NFS_SERVER(ino)->roc_rpcwaitq, task, NULL);
-
         return sleep;
 }