ext4: Replace lock/unlock_super() with an explicit lock for resizing
    
Use a separate lock to protect s_groups_count and the other block
group descriptors which get changed via an on-line resize operation,
so we can stop overloading the use of lock_super().
    
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7f43fde..1fbf090 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2646,6 +2646,7 @@
 #endif
 	INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
 	mutex_init(&sbi->s_orphan_lock);
+	mutex_init(&sbi->s_resize_lock);
 
 	sb->s_root = NULL;