No need to do lock_super() for exclusion in generic_shutdown_super() (a9e220f8) · Commits · 戴 / test

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

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);

fs/super.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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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