afs: Calculate lock extend timer from set/extend reply reception

Record the timestamp on the first reply DATA packet received in response to
a set- or extend-lock operation, then use this to calculate the time
remaining till the lock expires rather than using whatever time the
requesting process wakes up and finishes processing the operation as a
base.
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/flock.c

@@ -40,8 +40,34 @@ void afs_lock_may_be_available(struct afs_vnode *vnode)
  */
 static void afs_schedule_lock_extension(struct afs_vnode *vnode)
 {
-	queue_delayed_work(afs_lock_manager, &vnode->lock_work,
-			   AFS_LOCKWAIT * HZ / 2);
+	ktime_t expires_at, now, duration;
+	u64 duration_j;
+
+	expires_at = ktime_add_ms(vnode->locked_at, AFS_LOCKWAIT * 1000 / 2);
+	now = ktime_get_real();
+	duration = ktime_sub(expires_at, now);
+	if (duration <= 0)
+		duration_j = 0;
+	else
+		duration_j = nsecs_to_jiffies(ktime_to_ns(duration));
+
+	queue_delayed_work(afs_lock_manager, &vnode->lock_work, duration_j);
+}
+
+/*
+ * In the case of successful completion of a lock operation, record the time
+ * the reply appeared and start the lock extension timer.
+ */
+void afs_lock_op_done(struct afs_call *call)
+{
+	struct afs_vnode *vnode = call->reply[0];
+
+	if (call->error == 0) {
+		spin_lock(&vnode->lock);
+		vnode->locked_at = call->reply_time;
+		afs_schedule_lock_extension(vnode);
+		spin_unlock(&vnode->lock);
+	}
 }
 
 /*

fs/afs/fsclient.c

@@ -1845,6 +1845,7 @@ static const struct afs_call_type afs_RXFSSetLock = {
 	.name		= "FS.SetLock",
 	.op		= afs_FS_SetLock,
 	.deliver	= afs_deliver_fs_xxxx_lock,
+	.done		= afs_lock_op_done,
 	.destructor	= afs_flat_call_destructor,
 };
 
@@ -1855,6 +1856,7 @@ static const struct afs_call_type afs_RXFSExtendLock = {
 	.name		= "FS.ExtendLock",
 	.op		= afs_FS_ExtendLock,
 	.deliver	= afs_deliver_fs_xxxx_lock,
+	.done		= afs_lock_op_done,
 	.destructor	= afs_flat_call_destructor,
 };
 
@@ -1889,6 +1891,7 @@ int afs_fs_set_lock(struct afs_fs_cursor *fc, afs_lock_type_t type)
 
 	call->key = fc->key;
 	call->reply[0] = vnode;
+	call->want_reply_time = true;
 
 	/* marshall the parameters */
 	bp = call->request;
@@ -1925,6 +1928,7 @@ int afs_fs_extend_lock(struct afs_fs_cursor *fc)
 
 	call->key = fc->key;
 	call->reply[0] = vnode;
+	call->want_reply_time = true;
 
 	/* marshall the parameters */
 	bp = call->request;

fs/afs/internal.h

@@ -638,6 +638,7 @@ struct afs_vnode {
 	struct list_head	granted_locks;	/* locks granted on this file */
 	struct delayed_work	lock_work;	/* work to be done in locking */
 	struct key		*lock_key;	/* Key to be used in lock ops */
+	ktime_t			locked_at;	/* Time at which lock obtained */
 	enum afs_lock_state	lock_state : 8;
 	afs_lock_type_t		lock_type : 8;
 
@@ -905,6 +906,7 @@ extern void afs_put_read(struct afs_read *);
  */
 extern struct workqueue_struct *afs_lock_manager;
 
+extern void afs_lock_op_done(struct afs_call *);
 extern void afs_lock_work(struct work_struct *);
 extern void afs_lock_may_be_available(struct afs_vnode *);
 extern int afs_lock(struct file *, int, struct file_lock *);

fs/afs/yfsclient.c

@@ -1801,6 +1801,7 @@ static const struct afs_call_type yfs_RXYFSSetLock = {
 	.name		= "YFS.SetLock",
 	.op		= yfs_FS_SetLock,
 	.deliver	= yfs_deliver_fs_xxxx_lock,
+	.done		= afs_lock_op_done,
 	.destructor	= afs_flat_call_destructor,
 };
 
@@ -1811,6 +1812,7 @@ static const struct afs_call_type yfs_RXYFSExtendLock = {
 	.name		= "YFS.ExtendLock",
 	.op		= yfs_FS_ExtendLock,
 	.deliver	= yfs_deliver_fs_xxxx_lock,
+	.done		= afs_lock_op_done,
 	.destructor	= afs_flat_call_destructor,
 };
 
@@ -1847,6 +1849,7 @@ int yfs_fs_set_lock(struct afs_fs_cursor *fc, afs_lock_type_t type)
 
 	call->key = fc->key;
 	call->reply[0] = vnode;
+	call->want_reply_time = true;
 
 	/* marshall the parameters */
 	bp = call->request;
@@ -1884,6 +1887,7 @@ int yfs_fs_extend_lock(struct afs_fs_cursor *fc)
 
 	call->key = fc->key;
 	call->reply[0] = vnode;
+	call->want_reply_time = true;
 
 	/* marshall the parameters */
 	bp = call->request;