Sync timestamp changes for inodes of special files to disk as late

as possible (when the inode is reclaimed).  Temporarily only do
this if option UFS_LAZYMOD configured and softupdates aren't enabled.
UFS_LAZYMOD is intentionally left out of /sys/conf/options.

This is mainly to avoid almost useless disk i/o on battery powered
machines.  It's silly to write to disk (on the next sync or when the
inode becomes inactive) just because someone hit a key or something
wrote to the screen or /dev/null.

PR:		5577
Previous version reviewed by:	phk

1 files changed, 7 insertions, 7 deletions

diff --git a/sys/gnu/ext2fs/ext2_inode.c b/sys/gnu/ext2fs/ext2_inode.c
index a094ad2..ae37b2c8 100644
--- a/sys/gnu/ext2fs/ext2_inode.c
+++ b/sys/gnu/ext2fs/ext2_inode.c
@@ -72,12 +72,12 @@ ext2_init(struct vfsconf *vfsp)
 
 /*
  * Update the access, modified, and inode change times as specified by the
- * IACCESS, IUPDATE, and ICHANGE flags respectively. The IMODIFIED flag is
- * used to specify that the inode needs to be updated but that the times have
- * already been set. The access and modified times are taken from the second
- * and third parameters; the inode change time is always taken from the current
- * time. If waitfor is set, then wait for the disk write of the inode to
- * complete.
+ * IN_ACCESS, IN_UPDATE, and IN_CHANGE flags respectively.  Write the inode
+ * to disk if the IN_MODIFIED flag is set (it may be set initially, or by
+ * the timestamp update).  The IN_LAZYMOD flag is set to force a write
+ * later if not now.  If we write now, then clear both IN_MODIFIED and
+ * IN_LAZYMOD to reflect the presumably successful write, and if waitfor is
+ * set, then wait for the write to complete.
  */
 int
 ext2_update(vp, access, modify, waitfor)
@@ -95,7 +95,7 @@ ext2_update(vp, access, modify, waitfor)
 	ip = VTOI(vp);
 	if ((ip->i_flag & IN_MODIFIED) == 0)
 		return (0);
-	ip->i_flag &= ~IN_MODIFIED;
+	ip->i_flag &= ~(IN_LAZYMOD | IN_MODIFIED);
 	if (vp->v_mount->mnt_flag & MNT_RDONLY)
 		return (0);
 	fs = ip->i_e2fs;