locks: generic_delete_lease doesn't need a file_lock at all

Ensure that it's OK to pass in a NULL file_lock double pointer on
a F_UNLCK request and convert the vfs_setlease F_UNLCK callers to
do just that.

Finally, turn the BUG_ON in generic_setlease into a WARN_ON_ONCE
with an error return. That's a problem we can handle without
crashing the box if it occurs.
Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/locks.c

@@ -1637,22 +1637,23 @@ static int generic_add_lease(struct file *filp, long arg, struct file_lock **flp
 	return error;
 }
 
-static int generic_delete_lease(struct file *filp, struct file_lock **flp)
+static int generic_delete_lease(struct file *filp)
 {
+	int error = -EAGAIN;
 	struct file_lock *fl, **before;
 	struct dentry *dentry = filp->f_path.dentry;
 	struct inode *inode = dentry->d_inode;
 
-	trace_generic_delete_lease(inode, *flp);
-
 	for (before = &inode->i_flock;
 			((fl = *before) != NULL) && IS_LEASE(fl);
 			before = &fl->fl_next) {
-		if (fl->fl_file != filp)
-			continue;
-		return (*flp)->fl_lmops->lm_change(before, F_UNLCK);
+		if (fl->fl_file == filp)
+			break;
 	}
-	return -EAGAIN;
+	trace_generic_delete_lease(inode, fl);
+	if (fl)
+		error = fl->fl_lmops->lm_change(before, F_UNLCK);
+	return error;
 }
 
 /**
@@ -1682,13 +1683,15 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
 
 	time_out_leases(inode);
 
-	BUG_ON(!(*flp)->fl_lmops->lm_break);
-
 	switch (arg) {
 	case F_UNLCK:
-		return generic_delete_lease(filp, flp);
+		return generic_delete_lease(filp);
 	case F_RDLCK:
 	case F_WRLCK:
+		if (!(*flp)->fl_lmops->lm_break) {
+			WARN_ON_ONCE(1);
+			return -ENOLCK;
+		}
 		return generic_add_lease(filp, arg, flp);
 	default:
 		return -EINVAL;
@@ -1744,15 +1747,6 @@ int vfs_setlease(struct file *filp, long arg, struct file_lock **lease)
 }
 EXPORT_SYMBOL_GPL(vfs_setlease);
 
-static int do_fcntl_delete_lease(struct file *filp)
-{
-	struct file_lock fl, *flp = &fl;
-
-	lease_init(filp, F_UNLCK, flp);
-
-	return vfs_setlease(filp, F_UNLCK, &flp);
-}
-
 static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
 {
 	struct file_lock *fl, *ret;
@@ -1809,7 +1803,7 @@ static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
 int fcntl_setlease(unsigned int fd, struct file *filp, long arg)
 {
 	if (arg == F_UNLCK)
-		return do_fcntl_delete_lease(filp);
+		return vfs_setlease(filp, F_UNLCK, NULL);
 	return do_fcntl_add_lease(fd, filp, arg);
 }
 

fs/nfsd/nfs4state.c

@@ -690,7 +690,7 @@ static void nfs4_put_deleg_lease(struct nfs4_file *fp)
 	spin_unlock(&fp->fi_lock);
 
 	if (filp) {
-		vfs_setlease(filp, F_UNLCK, &fl);
+		vfs_setlease(filp, F_UNLCK, NULL);
 		fput(filp);
 	}
 }

include/trace/events/filelock.h

@@ -53,15 +53,15 @@ DECLARE_EVENT_CLASS(filelock_lease,
 	),
 
 	TP_fast_assign(
-		__entry->fl = fl;
+		__entry->fl = fl ? fl : NULL;
 		__entry->s_dev = inode->i_sb->s_dev;
 		__entry->i_ino = inode->i_ino;
-		__entry->fl_next = fl->fl_next;
-		__entry->fl_owner = fl->fl_owner;
-		__entry->fl_flags = fl->fl_flags;
-		__entry->fl_type = fl->fl_type;
-		__entry->fl_break_time = fl->fl_break_time;
-		__entry->fl_downgrade_time = fl->fl_downgrade_time;
+		__entry->fl_next = fl ? fl->fl_next : NULL;
+		__entry->fl_owner = fl ? fl->fl_owner : NULL;
+		__entry->fl_flags = fl ? fl->fl_flags : 0;
+		__entry->fl_type = fl ? fl->fl_type : 0;
+		__entry->fl_break_time = fl ? fl->fl_break_time : 0;
+		__entry->fl_downgrade_time = fl ? fl->fl_downgrade_time : 0;
 	),
 
 	TP_printk("fl=0x%p dev=0x%x:0x%x ino=0x%lx fl_next=0x%p fl_owner=0x%p fl_flags=%s fl_type=%s fl_break_time=%lu fl_downgrade_time=%lu",