[PATCH 2/2] ->write_super lock_super pushdown

[Christoph Hellwig <hch@lst.de>]

Push down lock_super into ->write_super instances and remove it from the
caller.

Following filesystem don't need ->s_lock in ->write_super and are skipped:

 * bfs, nilfs2 - no other uses of s_lock and have internal locks in
	->write_super
 * ext2 - uses BKL in ext2_write_super and has internal calls without s_lock
 * reiserfs - no other uses of s_lock as has reiserfs_write_lock (BKL) in
 	->write_super
 * xfs - no other uses of s_lock and uses internal lock (buffer lock on
	superblock buffer) to serialize ->write_super.  Also xfs_fs_write_super 
	is superflous and will go away in the next merge window


Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: vfs-2.6/fs/ext4/super.c
===================================================================
--- vfs-2.6.orig/fs/ext4/super.c	2009-05-11 23:26:24.844787452 +0200
+++ vfs-2.6/fs/ext4/super.c	2009-05-11 23:28:12.925808532 +0200
@@ -66,6 +66,7 @@ static int ext4_remount(struct super_blo
 static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf);
 static int ext4_unfreeze(struct super_block *sb);
 static void ext4_write_super(struct super_block *sb);
+static void ext4_write_super_locked(struct super_block *sb);
 static int ext4_freeze(struct super_block *sb);
 
 
@@ -566,7 +567,7 @@ static void ext4_put_super(struct super_
 	lock_super(sb);
 	lock_kernel();
 	if (sb->s_dirt)
-		ext4_write_super(sb);
+		ext4_write_super_locked(sb);
 
 	ext4_mb_release(sb);
 	ext4_ext_release(sb);
@@ -3273,7 +3274,7 @@ int ext4_force_commit(struct super_block
  * point.  (We can probably nuke this function altogether, and remove
  * any mention to sb->s_dirt in all of fs/ext4; eventual cleanup...)
  */
-static void ext4_write_super(struct super_block *sb)
+static void ext4_write_super_locked(struct super_block *sb)
 {
 	if (EXT4_SB(sb)->s_journal) {
 		if (mutex_trylock(&sb->s_lock) != 0)
@@ -3284,6 +3285,13 @@ static void ext4_write_super(struct supe
 	}
 }
 
+static void ext4_write_super(struct super_block *sb)
+{
+	lock_super(sb);
+	ext4_write_super_locked(sb);
+	unlock_super(sb);
+}
+
 static int ext4_sync_fs(struct super_block *sb, int wait)
 {
 	int ret = 0;
Index: vfs-2.6/fs/fat/inode.c
===================================================================
--- vfs-2.6.orig/fs/fat/inode.c	2009-05-11 23:26:24.862786880 +0200
+++ vfs-2.6/fs/fat/inode.c	2009-05-11 23:28:12.925808532 +0200
@@ -441,10 +441,12 @@ static void fat_clear_inode(struct inode
 
 static void fat_write_super(struct super_block *sb)
 {
+	lock_super(sb);
 	sb->s_dirt = 0;
 
 	if (!(sb->s_flags & MS_RDONLY))
 		fat_clusters_flush(sb);
+	unlock_super(sb);
 }
 
 static void fat_put_super(struct super_block *sb)
Index: vfs-2.6/fs/super.c
===================================================================
--- vfs-2.6.orig/fs/super.c	2009-05-11 23:26:24.882820644 +0200
+++ vfs-2.6/fs/super.c	2009-05-11 23:28:12.926784214 +0200
@@ -420,10 +420,8 @@ restart:
 			spin_unlock(&sb_lock);
 
 			down_read(&sb->s_umount);
-			lock_super(sb);
 			if (sb->s_root && sb->s_dirt)
 				sb->s_op->write_super(sb);
-			unlock_super(sb);
 			up_read(&sb->s_umount);
 
 			spin_lock(&sb_lock);
Index: vfs-2.6/fs/sysv/inode.c
===================================================================
--- vfs-2.6.orig/fs/sysv/inode.c	2009-05-11 23:26:24.907820404 +0200
+++ vfs-2.6/fs/sysv/inode.c	2009-05-11 23:28:12.926784214 +0200
@@ -37,6 +37,7 @@ static void sysv_write_super(struct supe
 	struct sysv_sb_info *sbi = SYSV_SB(sb);
 	unsigned long time = get_seconds(), old_time;
 
+	lock_super(sb);
 	lock_kernel();
 	if (sb->s_flags & MS_RDONLY)
 		goto clean;
@@ -56,6 +57,7 @@ static void sysv_write_super(struct supe
 clean:
 	sb->s_dirt = 0;
 	unlock_kernel();
+	unlock_super(sb);
 }
 
 static int sysv_remount(struct super_block *sb, int *flags, char *data)
Index: vfs-2.6/fs/ufs/super.c
===================================================================
--- vfs-2.6.orig/fs/ufs/super.c	2009-05-11 23:26:24.931820805 +0200
+++ vfs-2.6/fs/ufs/super.c	2009-05-11 23:28:12.927812907 +0200
@@ -1131,6 +1131,7 @@ static void ufs_write_super(struct super
 	struct ufs_super_block_third * usb3;
 	unsigned flags;
 
+	lock_super(sb);
 	lock_kernel();
 	UFSD("ENTER\n");
 	flags = UFS_SB(sb)->s_flags;
@@ -1150,6 +1151,7 @@ static void ufs_write_super(struct super
 	sb->s_dirt = 0;
 	UFSD("EXIT\n");
 	unlock_kernel();
+	unlock_super(sb);
 }
 
 static void ufs_put_super(struct super_block *sb)
Index: vfs-2.6/fs/affs/super.c
===================================================================
--- vfs-2.6.orig/fs/affs/super.c	2009-05-11 23:26:24.949786640 +0200
+++ vfs-2.6/fs/affs/super.c	2009-05-11 23:28:12.928818062 +0200
@@ -54,6 +54,7 @@ affs_write_super(struct super_block *sb)
 	int clean = 2;
 	struct affs_sb_info *sbi = AFFS_SB(sb);
 
+	lock_super(sb);
 	if (!(sb->s_flags & MS_RDONLY)) {
 		//	if (sbi->s_bitmap[i].bm_bh) {
 		//		if (buffer_dirty(sbi->s_bitmap[i].bm_bh)) {
@@ -66,6 +67,7 @@ affs_write_super(struct super_block *sb)
 		sb->s_dirt = !clean;	/* redo until bitmap synced */
 	} else
 		sb->s_dirt = 0;
+	unlock_super(sb);
 
 	pr_debug("AFFS: write_super() at %lu, clean=%d\n", get_seconds(), clean);
 }
Index: vfs-2.6/fs/exofs/super.c
===================================================================
--- vfs-2.6.orig/fs/exofs/super.c	2009-05-11 23:26:24.971786995 +0200
+++ vfs-2.6/fs/exofs/super.c	2009-05-11 23:28:12.929808342 +0200
@@ -214,6 +214,7 @@ static void exofs_write_super(struct sup
 		return;
 	}
 
+	lock_super(sb);
 	lock_kernel();
 	sbi = sb->s_fs_info;
 	fscb->s_nextid = cpu_to_le64(sbi->s_nextid);
@@ -246,6 +247,7 @@ out:
 	if (or)
 		osd_end_request(or);
 	unlock_kernel();
+	unlock_super(sb);
 	kfree(fscb);
 }
 
Index: vfs-2.6/fs/hfs/super.c
===================================================================
--- vfs-2.6.orig/fs/hfs/super.c	2009-05-11 23:26:24.990787179 +0200
+++ vfs-2.6/fs/hfs/super.c	2009-05-11 23:28:12.930808120 +0200
@@ -49,11 +49,13 @@ MODULE_LICENSE("GPL");
  */
 static void hfs_write_super(struct super_block *sb)
 {
+	lock_super(sb);
 	sb->s_dirt = 0;
-	if (sb->s_flags & MS_RDONLY)
-		return;
+
 	/* sync everything to the buffers */
-	hfs_mdb_commit(sb);
+	if (!(sb->s_flags & MS_RDONLY))
+		hfs_mdb_commit(sb);
+	unlock_super(sb);
 }
 
 /*
Index: vfs-2.6/fs/hfsplus/super.c
===================================================================
--- vfs-2.6.orig/fs/hfsplus/super.c	2009-05-11 23:26:25.008788283 +0200
+++ vfs-2.6/fs/hfsplus/super.c	2009-05-11 23:28:12.930808120 +0200
@@ -157,10 +157,12 @@ static void hfsplus_write_super(struct s
 	struct hfsplus_vh *vhdr = HFSPLUS_SB(sb).s_vhdr;
 
 	dprint(DBG_SUPER, "hfsplus_write_super\n");
+
+	lock_super(sb);
 	sb->s_dirt = 0;
 	if (sb->s_flags & MS_RDONLY)
 		/* warn? */
-		return;
+		goto out;
 
 	vhdr->free_blocks = cpu_to_be32(HFSPLUS_SB(sb).free_blocks);
 	vhdr->next_alloc = cpu_to_be32(HFSPLUS_SB(sb).next_alloc);
@@ -192,6 +194,8 @@ static void hfsplus_write_super(struct s
 		}
 		HFSPLUS_SB(sb).flags &= ~HFSPLUS_SB_WRITEBACKUP;
 	}
+ out:
+	unlock_super(sb);
 }
 
 static void hfsplus_put_super(struct super_block *sb)
Index: vfs-2.6/fs/jffs2/super.c
===================================================================
--- vfs-2.6.orig/fs/jffs2/super.c	2009-05-11 23:26:25.035786621 +0200
+++ vfs-2.6/fs/jffs2/super.c	2009-05-11 23:28:12.931808177 +0200
@@ -56,15 +56,18 @@ static void jffs2_i_init_once(void *foo)
 static void jffs2_write_super(struct super_block *sb)
 {
 	struct jffs2_sb_info *c = JFFS2_SB_INFO(sb);
+
+	lock_super(sb);
 	sb->s_dirt = 0;
 
-	if (sb->s_flags & MS_RDONLY)
-		return;
+	if (!(sb->s_flags & MS_RDONLY)) {
+		D1(printk(KERN_DEBUG "jffs2_write_super()\n"));
+		jffs2_garbage_collect_trigger(c);
+		jffs2_erase_pending_blocks(c, 0);
+		jffs2_flush_wbuf_gc(c, 0);
+	}
 
-	D1(printk(KERN_DEBUG "jffs2_write_super()\n"));
-	jffs2_garbage_collect_trigger(c);
-	jffs2_erase_pending_blocks(c, 0);
-	jffs2_flush_wbuf_gc(c, 0);
+	unlock_super(sb);
 }
 
 static int jffs2_sync_fs(struct super_block *sb, int wait)
Index: vfs-2.6/fs/sync.c
===================================================================
--- vfs-2.6.orig/fs/sync.c	2009-05-11 23:28:41.043659008 +0200
+++ vfs-2.6/fs/sync.c	2009-05-11 23:29:04.202661387 +0200
@@ -33,10 +33,8 @@ static int __sync_filesystem(struct supe
 	else
 		sync_quota_sb(sb, -1);
 	sync_inodes_sb(sb, wait);
-	lock_super(sb);
 	if (sb->s_dirt && sb->s_op->write_super)
 		sb->s_op->write_super(sb);
-	unlock_super(sb);
 	if (sb->s_op->sync_fs)
 		sb->s_op->sync_fs(sb, wait);
 	return __sync_blockdev(sb->s_bdev, wait);
@@ -164,10 +162,8 @@ int file_fsync(struct file *filp, struct
 
 	/* sync the superblock to buffers */
 	sb = inode->i_sb;
-	lock_super(sb);
 	if (sb->s_dirt && sb->s_op->write_super)
 		sb->s_op->write_super(sb);
-	unlock_super(sb);
 
 	/* .. finally sync the buffers to disk */
 	err = sync_blockdev(sb->s_bdev);