linux-kernel - [PATCH] relatime: Let relatime update atime at least once per day

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Message-ID: <20081202171926.GB20405@srcf.ucam.org>
Date:	Tue, 2 Dec 2008 17:19:26 +0000
From:	Matthew Garrett <mjg@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-fsdevel@...r.kernel.org, mingo@...hat.com,
	val.henson@...il.com
Subject: [PATCH] relatime: Let relatime update atime at least once per day

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.
    
Signed-off-by: Matthew Garrett <mjg@...hat.com>
Acked-by: Ingo Molnar <mingo@...hat.com>
Acked-by: Alan Cox <alan@...hat.com>

---

I've removed the adjustable time code, since nobody's come up with a 
terribly good use case for it. This makes relatime more useful in the 
generic case - there may be situations where it still doesn't satisfy 
people, but that's not a regression over the current situation.

diff --git a/fs/inode.c b/fs/inode.c
index 0487ddb..057c92b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1179,6 +1179,40 @@ sector_t bmap(struct inode * inode, sector_t block)
 }
 EXPORT_SYMBOL(bmap);
 
+/*
+ * With relative atime, only update atime if the previous atime is
+ * earlier than either the ctime or mtime or if at least a day has
+ * passed since the last atime update.
+ */
+static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
+			     struct timespec now)
+{
+
+	if (!(mnt->mnt_flags & MNT_RELATIME))
+		return 1;
+	/*
+	 * 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 a day? If yes,
+	 * update atime:
+	 */
+	if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)
+		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 +1240,12 @@ 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 (!relatime_need_update(mnt, inode, now))
+		goto out;
+
 	if (timespec_equal(&inode->i_atime, &now))
 		goto out;

-- 
Matthew Garrett | mjg59@...f.ucam.org
--
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