NFS: Replace flush_scheduled_work with cancel_work_sync() and friends

This will avoid deadlocks of the form:

stack backtrace:
 [<c0104fda>] show_trace_log_lvl+0x1a/0x30
 [<c0105c02>] show_trace+0x12/0x20
 [<c0105d15>] dump_stack+0x15/0x20
 [<c013ee42>] __lock_acquire+0xc22/0x1030
 [<c013f2b1>] lock_acquire+0x61/0x80
 [<c012edd9>] flush_workqueue+0x49/0x70
 [<c012ee0d>] flush_scheduled_work+0xd/0x10
 [<dcf55c0c>] nfs_release_automount_timer+0x2c/0x30 [nfs]
 [<dcf45d8e>] nfs_free_server+0x9e/0xd0 [nfs]
 [<dcf4e626>] nfs_kill_super+0x16/0x20 [nfs]
 [<c017b38d>] deactivate_super+0x7d/0xa0
 [<c018f94b>] mntput_no_expire+0x4b/0x80
 [<c018fd94>] expire_mount_list+0xe4/0x140
 [<c0191219>] mark_mounts_for_expiry+0x99/0xb0
 [<dcf55d1d>] nfs_expire_automounts+0xd/0x40 [nfs]
 [<c012e61b>] run_workqueue+0x12b/0x1e0
 [<c012f05b>] worker_thread+0x9b/0x100
 [<c0131c72>] kthread+0x42/0x70
 [<c0104c0f>] kernel_thread_helper+0x7/0x18
 =======================

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

1 files changed, 2 insertions, 4 deletions

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 7f86e65182e4..aea76d0e5fbd 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -175,10 +175,8 @@ static void nfs_expire_automounts(struct work_struct *work)
 
 void nfs_release_automount_timer(void)
 {
-        if (list_empty(&nfs_automount_list)) {
-                cancel_delayed_work(&nfs_automount_task);
-                flush_scheduled_work();
-        }
+        if (list_empty(&nfs_automount_list))
+                cancel_delayed_work_sync(&nfs_automount_task);
 }
 
 /*