fs/sysv: stop using write_super and s_dirt

It does not look like sysv FS needs 'write_super()' at all, because all it
does is a timestamp update. I cannot test this patch, because this
file-system is so old and probably has not been used by anyone for years,
so there are no tools to create it in Linux. But from the code I see that
marking the superblock as dirty is basically marking the superblock buffers as
drity and then setting the s_dirt flag. And when 'write_super()' is executed to
handle the s_dirt flag, we just update the timestamp and again mark the
superblock buffer as dirty. Seems pointless.

It looks like we can update the timestamp more opprtunistically - on unmount
or remount of sync, and nothing should change.

Thus, this patch removes 'sysv_write_super()' and 's_dirt'.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/sysv/inode.c

@@ -43,7 +43,6 @@ static int sysv_sync_fs(struct super_block *sb, int wait)
 	 * then attach current time stamp.
 	 * But if the filesystem was marked clean, keep it clean.
 	 */
-	sb->s_dirt = 0;
 	old_time = fs32_to_cpu(sbi, *sbi->s_sb_time);
 	if (sbi->s_type == FSTYPE_SYSV4) {
 		if (*sbi->s_sb_state == cpu_to_fs32(sbi, 0x7c269d38 - old_time))
@@ -57,14 +56,6 @@ static int sysv_sync_fs(struct super_block *sb, int wait)
 	return 0;
 }
 
-static void sysv_write_super(struct super_block *sb)
-{
-	if (!(sb->s_flags & MS_RDONLY))
-		sysv_sync_fs(sb, 1);
-	else
-		sb->s_dirt = 0;
-}
-
 static int sysv_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct sysv_sb_info *sbi = SYSV_SB(sb);
@@ -351,7 +342,6 @@ const struct super_operations sysv_sops = {
 	.write_inode	= sysv_write_inode,
 	.evict_inode	= sysv_evict_inode,
 	.put_super	= sysv_put_super,
-	.write_super	= sysv_write_super,
 	.sync_fs	= sysv_sync_fs,
 	.remount_fs	= sysv_remount,
 	.statfs		= sysv_statfs,

fs/sysv/sysv.h

@@ -117,7 +117,6 @@ static inline void dirty_sb(struct super_block *sb)
 	mark_buffer_dirty(sbi->s_bh1);
 	if (sbi->s_bh1 != sbi->s_bh2)
 		mark_buffer_dirty(sbi->s_bh2);
-	sb->s_dirt = 1;
 }