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

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From: Linux Kernel Mailing List
Date: Thursday, June 11, 2009 - 8:59 pm

Gitweb:     http://git.kernel.org/linus/a9e220f8322e2b0e0b8903fe00265461cffad3f0
Commit:     a9e220f8322e2b0e0b8903fe00265461cffad3f0
Parent:     62c6943b4b1e818aea60c11c5a68a50785b83119
Author:     Al Viro <viro@zeniv.linux.org.uk>
AuthorDate: Tue May 5 22:10:44 2009 -0400
Committer:  Al Viro <viro@zeniv.linux.org.uk>
CommitDate: Thu Jun 11 21:36:07 2009 -0400

    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>
---
 fs/ext4/super.c |    2 +-
 fs/super.c      |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c7b8f8d..0d3034c 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 49f670c..54fd331 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() */
--
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No need to do lock_super() for exclusion in generic_shutdo ..., Linux Kernel Mailing ..., (Thu Jun 11, 8:59 pm)