linux-kernel - [PATCH v2 1/2] relatime: Make relatime behaviour smarter

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Message-ID: <20081127150126.GA20941@srcf.ucam.org>
Date:	Thu, 27 Nov 2008 15:01:26 +0000
From:	Matthew Garrett <mjg@...hat.com>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	mingo@...hat.com, val.henson@...il.com, matthew@....cx
Subject: [PATCH v2 1/2] relatime: Make relatime behaviour smarter

Make relatime smarter
    
Allow atime to be updated once per day even with relatime. This lets
utilities like tmpreaper (which delete files based on last access time)
continue working.

---

Subset of Ingo's original patch, rediffed against current git

diff --git a/fs/inode.c b/fs/inode.c
index 0487ddb..348fa16 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1179,6 +1179,41 @@ sector_t bmap(struct inode * inode, sector_t block)
 }
 EXPORT_SYMBOL(bmap);
 
+/*
+ * Relative atime updates frequency (default: 1 day):
+ */
+int relatime_interval __read_mostly = 24*60*60;
+
+/*
+ * With relative atime, only update atime if the
+ * previous atime is earlier than either the ctime or
+ * mtime.
+ */
+static int relatime_need_update(struct inode *inode, struct timespec now)
+{
+	/*
+	 * Is mtime younger than atime? If yes, update atime:
+	 */
+	if (timespec_compare(&inode->i_mtime, &inode->i_atime) >= 0)
+		return 1;
+	/*
+	 * Is ctime younger than atime? If yes, update atime:
+	 */
+	if (timespec_compare(&inode->i_ctime, &inode->i_atime) >= 0)
+		return 1;
+
+	/*
+	 * Is the previous atime value older than the update interval?
+	 * If yes, update atime:
+	 */
+	if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= relatime_interval)
+		return 1;
+	/*
+	 * Good, we can skip the atime update:
+	 */
+	return 0;
+}
+
 /**
  *	touch_atime	-	update the access time
  *	@mnt: mount the inode is accessed on
@@ -1206,17 +1241,12 @@ void touch_atime(struct vfsmount *mnt, struct dentry *dentry)
 		goto out;
 	if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
 		goto out;
-	if (mnt->mnt_flags & MNT_RELATIME) {
-		/*
-		 * With relative atime, only update atime if the previous
-		 * atime is earlier than either the ctime or mtime.
-		 */
-		if (timespec_compare(&inode->i_mtime, &inode->i_atime) < 0 &&
-		    timespec_compare(&inode->i_ctime, &inode->i_atime) < 0)
-			goto out;
-	}
 
 	now = current_fs_time(inode->i_sb);
+
+	if (mnt->mnt_flags & MNT_RELATIME)
+		if (!relatime_need_update(inode, now))
+			goto out;
 	if (timespec_equal(&inode->i_atime, &now))
 		goto out;
 
-- 
Matthew Garrett | mjg59@...f.ucam.org
--
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