From: Naofumi Honda <honda@math.sci.hokudai.ac.jp>
Date: Thu, 9 Nov 2017 10:57:16 -0500
Subject: [PATCH] nfsd: fix panic in posix_unblock_lock called from
 nfs4_laundromat
Git-commit: 64ebe12494fd5d193f014ce38e1fd83cc57883c8
Patch-mainline: v4.15-rc2
References: git-fixes

From kernel 4.9, my two nfsv4 servers sometimes suffer from
    "panic: unable to handle kernel page request"
in posix_unblock_lock() called from nfs4_laundromat().

These panics diseappear if we revert the commit "nfsd: add a LRU list
for blocked locks".

The cause appears to be a typo in nfs4_laundromat(), which is also
present in nfs4_state_shutdown_net().

Cc: stable@vger.kernel.org
Fixes: 7919d0a27f1e "nfsd: add a LRU list for blocked locks"
Cc: jlayton@redhat.com
Reveiwed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfsd/nfs4state.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4664,7 +4664,7 @@ nfs4_laundromat(struct nfsd_net *nn)
 	spin_unlock(&nn->blocked_locks_lock);
 
 	while (!list_empty(&reaplist)) {
-		nbl = list_first_entry(&nn->blocked_locks_lru,
+		nbl = list_first_entry(&reaplist,
 					struct nfsd4_blocked_lock, nbl_lru);
 		list_del_init(&nbl->nbl_lru);
 		posix_unblock_lock(&nbl->nbl_lock);
@@ -7058,7 +7058,7 @@ nfs4_state_shutdown_net(struct net *net)
 	spin_unlock(&nn->blocked_locks_lock);
 
 	while (!list_empty(&reaplist)) {
-		nbl = list_first_entry(&nn->blocked_locks_lru,
+		nbl = list_first_entry(&reaplist,
 					struct nfsd4_blocked_lock, nbl_lru);
 		list_del_init(&nbl->nbl_lru);
 		posix_unblock_lock(&nbl->nbl_lock);