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>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c7b8f8d..0d3034c 100644 (file)
--- 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 49f670c..54fd331 100644 (file)
--- 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() */