Lazy atime - update the atime in the in-core inode, but don't mark the
inode dirty.  Atime only gets written out when the inode is dirtied
for some other reason.

Not for inclusion!

Written by Val Henson <val_henson@linux.intel.com>

 fs/inode.c            |    4 +++-
 fs/namespace.c        |    5 ++++-
 include/linux/fs.h    |    1 +
 include/linux/mount.h |    1 +
 4 files changed, 9 insertions(+), 2 deletions(-)
diff -Nru a/fs/inode.c b/fs/inode.c
--- a/fs/inode.c	2006-08-02 20:53:45 -07:00
+++ b/fs/inode.c	2006-08-02 20:53:45 -07:00
@@ -1202,7 +1202,9 @@
 	now = current_fs_time(inode->i_sb);
 	if (!timespec_equal(&inode->i_atime, &now)) {
 		inode->i_atime = now;
-		mark_inode_dirty_sync(inode);
+		/* Don't mark inode dirty if we are lazy about atime */
+		if (!(mnt && (mnt->mnt_flags & MNT_LAZYATIME)))
+			mark_inode_dirty_sync(inode);
 	}
 }
 
diff -Nru a/fs/namespace.c b/fs/namespace.c
--- a/fs/namespace.c	2006-08-02 20:53:45 -07:00
+++ b/fs/namespace.c	2006-08-02 20:53:45 -07:00
@@ -376,6 +376,7 @@
 		{ MNT_NOEXEC, ",noexec" },
 		{ MNT_NOATIME, ",noatime" },
 		{ MNT_NODIRATIME, ",nodiratime" },
+		{ MNT_LAZYATIME, ",lazyatime" },
 		{ 0, NULL }
 	};
 	struct proc_fs_info *fs_infop;
@@ -1413,9 +1414,11 @@
 		mnt_flags |= MNT_NOATIME;
 	if (flags & MS_NODIRATIME)
 		mnt_flags |= MNT_NODIRATIME;
+	if (flags & MS_LAZYATIME)
+		mnt_flags |= MNT_LAZYATIME;
 
 	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
-		   MS_NOATIME | MS_NODIRATIME);
+		   MS_NOATIME | MS_NODIRATIME | MS_LAZYATIME);
 
 	/* ... and get the mountpoint */
 	retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
diff -Nru a/include/linux/fs.h b/include/linux/fs.h
--- a/include/linux/fs.h	2006-08-02 20:53:45 -07:00
+++ b/include/linux/fs.h	2006-08-02 20:53:45 -07:00
@@ -119,6 +119,7 @@
 #define MS_PRIVATE	(1<<18)	/* change to private */
 #define MS_SLAVE	(1<<19)	/* change to slave */
 #define MS_SHARED	(1<<20)	/* change to shared */
+#define MS_LAZYATIME	(1<<21)	/* Lazily update on-disk access times. */
 #define MS_ACTIVE	(1<<30)
 #define MS_NOUSER	(1<<31)
 
diff -Nru a/include/linux/mount.h b/include/linux/mount.h
--- a/include/linux/mount.h	2006-08-02 20:53:45 -07:00
+++ b/include/linux/mount.h	2006-08-02 20:53:45 -07:00
@@ -27,6 +27,7 @@
 #define MNT_NOEXEC	0x04
 #define MNT_NOATIME	0x08
 #define MNT_NODIRATIME	0x10
+#define MNT_LAZYATIME	0x20
 
 #define MNT_SHRINKABLE	0x100