Allow relatime to update atime once a 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, making relatime a plausible default for distributions.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Valerie Aurora Henson <vaurora@redhat.com>
Acked-by: Alan Cox <alan@redhat.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 38 insertions, 9 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 826fb0b9d1c3..6ac0cef6c5f5 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1290,6 +1290,40 @@ 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
@@ -1317,17 +1351,12 @@ 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;