Re: [PATCH 2/2] ->write_super lock_super pushdown

[Christoph Hellwig <hch@lst.de>]

On Wed, May 06, 2009 at 10:16:31PM +0200, Christoph Hellwig wrote:
> Only four filesystems have both a ->write_super method and use lock_super
> internally: ext4, fat, sysv, ufs.  Push down lock_super into these
> filesystems and remove it from the caller.  Add a get_fs_excl/put_fs_excl
> pair to sync_super for now to keep the current behaviour in that
> respect.  Calling it a second time from write_super is fine as it's
> only checked for beeing non-zero.
> 
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Actually the patch lost two hunks due to missing quilt adds.  Here's the
complete one:


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

Index: vfs-2.6/fs/ext4/super.c
===================================================================
--- vfs-2.6.orig/fs/ext4/super.c	2009-05-06 22:23:00.016784345 +0200
+++ vfs-2.6/fs/ext4/super.c	2009-05-06 22:26:09.741784086 +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);
@@ -3273,17 +3274,22 @@ 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)
-			BUG();
 		sb->s_dirt = 0;
 	} else {
 		ext4_commit_super(sb, EXT4_SB(sb)->s_es, 1);
 	}
 }
 
+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	2009-05-06 22:23:00.021784213 +0200
+++ vfs-2.6/fs/fat/inode.c	2009-05-06 22:26:09.741784086 +0200
@@ -441,8 +441,10 @@ static void fat_clear_inode(struct inode
 
 static void fat_write_super(struct super_block *sb)
 {
+	lock_super(sb);
 	sb->s_dirt = 0;
 	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	2009-05-06 22:23:00.025787586 +0200
+++ vfs-2.6/fs/super.c	2009-05-06 22:26:09.742784073 +0200
@@ -421,7 +421,6 @@ restart:
 			spin_unlock(&sb_lock);
 
 			down_read(&sb->s_umount);
-			lock_super(sb);
 			if (sb->s_root) {
 				/*
 				 * Avoid loops if a filesystem left s_dirt
@@ -433,10 +432,12 @@ restart:
 				if (sb->s_flags & MS_RDONLY)
 					sb->s_dirt = 0;
 
-				if (sb->s_dirt)
+				if (sb->s_dirt) {
+					get_fs_excl();
 					sb->s_op->write_super(sb);
+					put_fs_excl();
+				}
 			}
-			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	2009-05-06 22:23:00.059784161 +0200
+++ vfs-2.6/fs/sysv/inode.c	2009-05-06 22:26:09.743783851 +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 we are going to write out the super block,
@@ -53,6 +54,7 @@ static void sysv_write_super(struct supe
 
 	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	2009-05-06 22:23:00.065784017 +0200
+++ vfs-2.6/fs/ufs/super.c	2009-05-06 22:26:09.743783851 +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;
@@ -1149,6 +1150,7 @@ 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/sync.c
===================================================================
--- vfs-2.6.orig/fs/sync.c	2009-05-06 22:28:49.598694594 +0200
+++ vfs-2.6/fs/sync.c	2009-05-06 22:29:48.860661341 +0200
@@ -31,10 +31,11 @@ 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)
+	if (sb->s_dirt && sb->s_op->write_super) {
+		get_fs_excl();
 		sb->s_op->write_super(sb);
-	unlock_super(sb);
+		put_fs_excl();
+	}
 	if (sb->s_op->sync_fs)
 		sb->s_op->sync_fs(sb, wait);
 	return __sync_blockdev(sb->s_bdev, wait);
@@ -162,10 +163,11 @@ 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)
+	if (sb->s_dirt && sb->s_op->write_super) {
+		get_fs_excl();
 		sb->s_op->write_super(sb);
-	unlock_super(sb);
+		put_fs_excl();
+	}
 
 	/* .. finally sync the buffers to disk */
 	err = sync_blockdev(sb->s_bdev);