[PATCH] relative atime

Add "relatime" (relative atime) support.  Relative atime only updates the
atime if the previous atime is older than the mtime or ctime.  Like
noatime, but useful for applications like mutt that need to know when a
file has been read since it was last modified.

A corresponding patch against mount(8) is available at
http://userweb.kernel.org/~akpm/mount-relative-atime.txt

Signed-off-by: Valerie Henson <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Karel Zak <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/fs/inode.c b/fs/inode.c
index 04536ebc5ac46c8012408168a87083fa442c3039..bf21dc6d0dbd752d243a2d3b6d92d2d554dc0381 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1177,13 +1177,27 @@ void touch_atime(struct vfsmount *mnt, struct dentry *dentry)
                        return;
                if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
                        return;
+
+               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)
+                               return;
+               }
        }
 
        now = current_fs_time(inode->i_sb);
-       if (!timespec_equal(&inode->i_atime, &now)) {
-               inode->i_atime = now;
-               mark_inode_dirty_sync(inode);
-       }
+       if (timespec_equal(&inode->i_atime, &now))
+               return;
+
+       inode->i_atime = now;
+       mark_inode_dirty_sync(inode);
 }
 EXPORT_SYMBOL(touch_atime);
 

diff --git a/fs/namespace.c b/fs/namespace.c
index fde8553faa7661677e2210d65620b753eceddaf8..5ef336c1103c2c4a4ecbb5c9bf96cf8923e15454 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -368,6 +368,7 @@ static int show_vfsmnt(struct seq_file *m, void *v)
                { MNT_NOEXEC, ",noexec" },
                { MNT_NOATIME, ",noatime" },
                { MNT_NODIRATIME, ",nodiratime" },
+               { MNT_RELATIME, ",relatime" },
                { 0, NULL }
        };
        struct proc_fs_info *fs_infop;
@@ -1405,9 +1406,11 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
                mnt_flags |= MNT_NOATIME;
        if (flags & MS_NODIRATIME)
                mnt_flags |= MNT_NODIRATIME;
+       if (flags & MS_RELATIME)
+               mnt_flags |= MNT_RELATIME;
 
        flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
-                  MS_NOATIME | MS_NODIRATIME);
+                  MS_NOATIME | MS_NODIRATIME | MS_RELATIME);
 
        /* ... and get the mountpoint */
        retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index adce6e1d70c2cf0c20ec97ce628df2307e025d55..186da813541e574128b1ea2772c8e6fa5e1007e7 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -120,6 +120,7 @@ extern int dir_notify_enable;
 #define MS_PRIVATE     (1<<18) /* change to private */
 #define MS_SLAVE       (1<<19) /* change to slave */
 #define MS_SHARED      (1<<20) /* change to shared */
+#define MS_RELATIME    (1<<21) /* Update atime relative to mtime/ctime. */
 #define MS_ACTIVE      (1<<30)
 #define MS_NOUSER      (1<<31)
 

diff --git a/include/linux/mount.h b/include/linux/mount.h
index e357dc86a4de304c0fd77cdcc83fce0ffa475319..1b7e178b0d8472549de308667343b15d4f44aa56 100644 (file)
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -27,6 +27,7 @@ struct mnt_namespace;
 #define MNT_NOEXEC     0x04
 #define MNT_NOATIME    0x08
 #define MNT_NODIRATIME 0x10
+#define MNT_RELATIME   0x20
 
 #define MNT_SHRINKABLE 0x100