Add a strictatime mount option

Add support for explicitly requesting full atime updates. This makes it
possible for kernels to default to relatime but still allow userspace to
override it.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 06f8e63..d0659ec 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -780,6 +780,7 @@ static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
                { MNT_NOATIME, ",noatime" },
                { MNT_NODIRATIME, ",nodiratime" },
                { MNT_RELATIME, ",relatime" },
+               { MNT_STRICTATIME, ",strictatime" },
                { 0, NULL }
        };
        const struct proc_fs_info *fs_infop;
@@ -1932,11 +1933,14 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
                mnt_flags |= MNT_NODIRATIME;
        if (flags & MS_RELATIME)
                mnt_flags |= MNT_RELATIME;
+       if (flags & MS_STRICTATIME)
+               mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
        if (flags & MS_RDONLY)
                mnt_flags |= MNT_READONLY;
 
        flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
-                  MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT);
+                  MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
+                  MS_STRICTATIME);
 
        /* ... and get the mountpoint */
        retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 92734c0..5bc81c4 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -141,6 +141,7 @@ struct inodes_stat_t {
 #define MS_RELATIME    (1<<21) /* Update atime relative to mtime/ctime. */
 #define MS_KERNMOUNT   (1<<22) /* this is a kern_mount call */
 #define MS_I_VERSION   (1<<23) /* Update inode I_version field */
+#define MS_STRICTATIME (1<<24) /* Always perform atime updates */
 #define MS_ACTIVE      (1<<30)
 #define MS_NOUSER      (1<<31)
 

diff --git a/include/linux/mount.h b/include/linux/mount.h
index cab2a85..51f55f9 100644 (file)
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -27,6 +27,7 @@ struct mnt_namespace;
 #define MNT_NODIRATIME 0x10
 #define MNT_RELATIME   0x20
 #define MNT_READONLY   0x40    /* does the user want this to be r/o? */
+#define MNT_STRICTATIME 0x80
 
 #define MNT_SHRINKABLE 0x100
 #define MNT_IMBALANCED_WRITE_COUNT     0x200 /* just for debugging */