[PATCH 1/2] locks: Introduce lm_breaker_timedout op to lease_manager_operations

[Dai Ngo <dai.ngo@oracle.com>]

Some consumers of the lease_manager_operations need to perform additional
actions when a lease break, triggered by a conflict, times out.

The NFS server is the first consumer of this operation.

When a pNFS layout conflict occurs, and the lease break times out -
resulting in the layout being revoked and its file_lease beeing removed
from the flc_lease list, the NFS server must issue a fence operation.
This ensures that the client is prevented from accessing the data
server after the layout is revoked.

Fixes: f99d4fbdae67 ("nfsd: add SCSI layout support")
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
---
 Documentation/filesystems/locking.rst |  2 ++
 fs/locks.c                            | 14 +++++++++++---
 include/linux/filelock.h              |  2 ++
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
index 77704fde9845..cd600db6c4b9 100644
--- a/Documentation/filesystems/locking.rst
+++ b/Documentation/filesystems/locking.rst
@@ -403,6 +403,7 @@ prototypes::
 	bool (*lm_breaker_owns_lease)(struct file_lock *);
         bool (*lm_lock_expirable)(struct file_lock *);
         void (*lm_expire_lock)(void);
+        void (*lm_breaker_timedout)(struct file_lease *);
 
 locking rules:
 
@@ -416,6 +417,7 @@ lm_change		yes		no			no
 lm_breaker_owns_lease:	yes     	no			no
 lm_lock_expirable	yes		no			no
 lm_expire_lock		no		no			yes
+lm_breaker_timedout     no              no                      yes
 ======================	=============	=================	=========
 
 buffer_head
diff --git a/fs/locks.c b/fs/locks.c
index 04a3f0e20724..1f254e0cd398 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -369,9 +369,15 @@ locks_dispose_list(struct list_head *dispose)
 	while (!list_empty(dispose)) {
 		flc = list_first_entry(dispose, struct file_lock_core, flc_list);
 		list_del_init(&flc->flc_list);
-		if (flc->flc_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
+		if (flc->flc_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT)) {
+			if (flc->flc_flags & FL_BREAKER_TIMEDOUT) {
+				struct file_lease *fl = file_lease(flc);
+
+				if (fl->fl_lmops->lm_breaker_timedout)
+					fl->fl_lmops->lm_breaker_timedout(fl);
+			}
 			locks_free_lease(file_lease(flc));
-		else
+		} else
 			locks_free_lock(file_lock(flc));
 	}
 }
@@ -1482,8 +1488,10 @@ static void time_out_leases(struct inode *inode, struct list_head *dispose)
 		trace_time_out_leases(inode, fl);
 		if (past_time(fl->fl_downgrade_time))
 			lease_modify(fl, F_RDLCK, dispose);
-		if (past_time(fl->fl_break_time))
+		if (past_time(fl->fl_break_time)) {
 			lease_modify(fl, F_UNLCK, dispose);
+			fl->c.flc_flags |= FL_BREAKER_TIMEDOUT;
+		}
 	}
 }
 
diff --git a/include/linux/filelock.h b/include/linux/filelock.h
index c2ce8ba05d06..06ccd6b66012 100644
--- a/include/linux/filelock.h
+++ b/include/linux/filelock.h
@@ -17,6 +17,7 @@
 #define FL_OFDLCK	1024	/* lock is "owned" by struct file */
 #define FL_LAYOUT	2048	/* outstanding pNFS layout */
 #define FL_RECLAIM	4096	/* reclaiming from a reboot server */
+#define	FL_BREAKER_TIMEDOUT	8192	/* lease breaker timed out */
 
 #define FL_CLOSE_POSIX (FL_POSIX | FL_CLOSE)
 
@@ -49,6 +50,7 @@ struct lease_manager_operations {
 	int (*lm_change)(struct file_lease *, int, struct list_head *);
 	void (*lm_setup)(struct file_lease *, void **);
 	bool (*lm_breaker_owns_lease)(struct file_lease *);
+	void (*lm_breaker_timedout)(struct file_lease *fl);
 };
 
 struct lock_manager {
-- 
2.47.3