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Date:	Wed, 11 Jul 2012 16:46:42 +0300
From:	Artem Bityutskiy <>
To:	Theodore Tso <>, Jan Kara <>
Cc:	Linux FS Maling List <>,
	Linux Kernel Maling List <>,
	Ext4 Mailing List <>
Subject: [PATCHv7 3/5] ext4: remove unnecessary superblock dirtying

From: Artem Bityutskiy <>

This patch changes the 'ext4_handle_dirty_super()' function which submits
the superblock for I/O in the following cases:

1. When creating the first large file on a file system without
2. When re-sizing the file-system.
3. When creating an xattr on a file-system without the

If the file-system has journal enabled, the superblock is written via the
journal. We do not modify this path.

If the file-system has no journal, this function, falls back to just marking
the superblock as dirty using the 's_dirt' superblock flag. This means that it
delays the actual superblock I/O submission by 5 seconds (default setting).
Namely, the 'sync_supers()' kernel thread will call 'ext4_write_super()' later
and will actually submit the superblock for I/O.

And this is the behavior this patch modifies: we stop using 's_dirt' and just
mark the superblock buffer as dirty right away. Indeed, all 3 cases above are
extremely rare and it does not add any value to delay the I/O submission for

Note: 'ext4_handle_dirty_super()' executes '__ext4_handle_dirty_super()' with
'now = 0'. This patch basically makes the 'now' argument unneeded and it will
be deleted in one of the next patches.

This patch also removes 's_dirt' condition on the unmount path because we never
set it anymore, so we should not test it.

Tested using xfstests for both journalled and non-journalled ext4.

Signed-off-by: Artem Bityutskiy <>
Reviewed-by: Jan Kara <>
 fs/ext4/ext4_jbd2.c |    5 ++---
 fs/ext4/super.c     |    2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index 90f7c2e..c19ab6a 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -151,11 +151,10 @@ int __ext4_handle_dirty_super(const char *where, unsigned int line,
 		if (err)
 			ext4_journal_abort_handle(where, line, __func__,
 						  bh, handle, err);
-	} else if (now) {
+	} else {
 				(struct ext4_super_block *)bh->b_data);
-	} else
-		sb->s_dirt = 1;
+	}
 	return err;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index eb7aa3e..a391c53 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -896,7 +896,7 @@ static void ext4_put_super(struct super_block *sb)
 		es->s_state = cpu_to_le16(sbi->s_mount_state);
-	if (sb->s_dirt || !(sb->s_flags & MS_RDONLY))
+	if (!(sb->s_flags & MS_RDONLY))
 		ext4_commit_super(sb, 1);
 	if (sbi->s_proc) {

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