commit 21f976975cbecbdaf23ceeacc1cab2b1c05a028e
Author: Jan Kara <jack@suse.cz>
Date:   Mon Apr 4 15:33:39 2011 -0400

    ext4: remove unnecessary [cm]time update of quota file

    It is not necessary to update [cm]time of quota file on each quota
    file write and it wastes journal space and IO throughput with inode
    writes. So just remove the updating from ext4_quota_write() and only
    update times when quotas are being turned off. Userspace cannot get
    anything reliable from quota files while they are used by the kernel
    anyway.

    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

Index: linux-stage/fs/ext4/ext4_jbd2.h
===================================================================
--- linux-stage.orig/fs/ext4/ext4_jbd2.h	2012-06-26 11:26:25.000000000 +0200
+++ linux-stage/fs/ext4/ext4_jbd2.h	2012-06-26 11:35:31.025105000 +0200
@@ -88,8 +88,8 @@
 
 #ifdef CONFIG_QUOTA
 /* Amount of blocks needed for quota update - we know that the structure was
- * allocated so we need to update only inode+data */
-#define EXT4_QUOTA_TRANS_BLOCKS(sb) (test_opt(sb, QUOTA) ? 2 : 0)
+ * allocated so we need to update only data block */
+#define EXT4_QUOTA_TRANS_BLOCKS(sb) (test_opt(sb, QUOTA) ? 1 : 0)
 /* Amount of blocks needed for quota insert/delete - we do some block writes
  * but inode, sb and group updates are done only once */
 #define EXT4_QUOTA_INIT_BLOCKS(sb) (test_opt(sb, QUOTA) ? (DQUOT_INIT_ALLOC*\
Index: linux-stage/fs/ext4/super.c
===================================================================
--- linux-stage.orig/fs/ext4/super.c	2012-06-26 11:35:09.000000000 +0200
+++ linux-stage/fs/ext4/super.c	2012-06-26 11:37:30.905374000 +0200
@@ -4582,6 +4582,7 @@ static int ext4_quota_on(struct super_bl
 static int ext4_quota_off(struct super_block *sb, int type, int remount)
 {
 	struct quota_info *dqopt = sb_dqopt(sb);
+	int                cnt;
 
 	mutex_lock(&dqopt->dqonoff_mutex);
 	if (!sb_any_quota_loaded(sb)) {
@@ -4598,6 +4599,37 @@ static int ext4_quota_off(struct super_b
 		up_read(&sb->s_umount);
 	}
 
+	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
+		struct inode      *inode;
+		handle_t          *handle;
+
+		if (type != -1 && cnt != type)
+			continue;
+
+		mutex_lock(&dqopt->dqonoff_mutex);
+		inode = dqopt->files[cnt];
+		if (!sb_has_quota_loaded(sb, cnt) || !inode) {
+			mutex_unlock(&dqopt->dqonoff_mutex);
+			continue;
+		}
+
+		inode = igrab(inode);
+		mutex_unlock(&dqopt->dqonoff_mutex);
+
+		if (!inode)
+			continue;
+
+		/* Update modification times of quota files when userspace can
+		 * start looking at them */
+		handle = ext4_journal_start(inode, 1);
+		if (!IS_ERR(handle)) {
+			inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+			ext4_mark_inode_dirty(handle, inode);
+			ext4_journal_stop(handle);
+		}
+		iput(inode);
+	}
+
 	return vfs_quota_off(sb, type, remount);
 }
 
@@ -4696,9 +4728,8 @@ out:
 	if (inode->i_size < off + len) {
 		i_size_write(inode, off + len);
 		EXT4_I(inode)->i_disksize = inode->i_size;
+		ext4_mark_inode_dirty(handle, inode);
 	}
-	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
-	ext4_mark_inode_dirty(handle, inode);
 	mutex_unlock(&inode->i_mutex);
 	return len;
 }