UBIFS: kill BKL

The BKL was pushed down from VFS to the file-systems. It used
to serialize mount/unmount/remount and prevented more than one
instance of the same file-system from doing
mount/umount/remount at the same time. But it is OK for UBIFS
and it does not need any additional locking for these cases.
Thus, kick the BKL out of UBIFS.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/super.c

@@ -36,7 +36,6 @@
 #include <linux/mount.h>
 #include <linux/math64.h>
 #include <linux/writeback.h>
-#include <linux/smp_lock.h>
 #include "ubifs.h"
 
 /*
@@ -1726,8 +1725,6 @@ static void ubifs_put_super(struct super_block *sb)
 	ubifs_msg("un-mount UBI device %d, volume %d", c->vi.ubi_num,
 		  c->vi.vol_id);
 
-	lock_kernel();
-
 	/*
 	 * The following asserts are only valid if there has not been a failure
 	 * of the media. For example, there will be dirty inodes if we failed
@@ -1792,8 +1789,6 @@ static void ubifs_put_super(struct super_block *sb)
 	ubi_close_volume(c->ubi);
 	mutex_unlock(&c->umount_mutex);
 	kfree(c);
-
-	unlock_kernel();
 }
 
 static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
@@ -1809,22 +1804,17 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
 		return err;
 	}
 
-	lock_kernel();
 	if ((sb->s_flags & MS_RDONLY) && !(*flags & MS_RDONLY)) {
 		if (c->ro_media) {
 			ubifs_msg("cannot re-mount due to prior errors");
-			unlock_kernel();
 			return -EROFS;
 		}
 		err = ubifs_remount_rw(c);
-		if (err) {
-			unlock_kernel();
+		if (err)
 			return err;
-		}
 	} else if (!(sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY)) {
 		if (c->ro_media) {
 			ubifs_msg("cannot re-mount due to prior errors");
-			unlock_kernel();
 			return -EROFS;
 		}
 		ubifs_remount_ro(c);
@@ -1839,7 +1829,6 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
 	}
 
 	ubifs_assert(c->lst.taken_empty_lebs > 0);
-	unlock_kernel();
 	return 0;
 }