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>

diff --git a/fs/inode.c b/fs/inode.c
index 826fb0b9d1c38f4dbe4ad16c6ec938a7e31cdc88..6ac0cef6c5f5aefd420af822c774b7122740065e 100644 (file)
--- 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;