No need to do lock_super() for exclusion in generic_shutdown_super()

We can't run into contention on it.  All other callers of lock_super()
either hold s_umount (and we have it exclusive) or hold an active
reference to superblock in question, which prevents the call of
generic_shutdown_super() while the reference is held.  So we can
replace lock_super(s) with get_fs_excl() in generic_shutdown_super()
(and corresponding change for unlock_super(), of course).

Since ext4 expects s_lock held for its put_super, take lock_super()
into it.  The rest of filesystems do not care at all.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 3 insertions, 3 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c7b8f8d9b7a8..0d3034c5e8a4 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -576,6 +576,7 @@ static void ext4_put_super(struct super_block *sb)
         struct ext4_super_block *es = sbi->s_es;
         int i, err;
 
+        lock_super(sb);
         if (sb->s_dirt)
                 ext4_write_super(sb);
 
@@ -645,7 +646,6 @@ static void ext4_put_super(struct super_block *sb)
         unlock_super(sb);
         kobject_put(&sbi->s_kobj);
         wait_for_completion(&sbi->s_kobj_unregister);
-        lock_super(sb);
         lock_kernel();
         kfree(sbi->s_blockgroup_lock);
         kfree(sbi);
diff --git a/fs/super.c b/fs/super.c
index 49f670cb9a83..54fd331f0cab 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -304,7 +304,7 @@ void generic_shutdown_super(struct super_block *sb)
         if (sb->s_root) {
                 shrink_dcache_for_umount(sb);
                 sync_filesystem(sb);
-                lock_super(sb);
+                get_fs_excl();
                 sb->s_flags &= ~MS_ACTIVE;
 
                 /* bad name - it should be evict_inodes() */
@@ -322,7 +322,7 @@ void generic_shutdown_super(struct super_block *sb)
                 }
 
                 unlock_kernel();
-                unlock_super(sb);
+                put_fs_excl();
         }
         spin_lock(&sb_lock);
         /* should be initialized for __put_super_and_need_restart() */