[PATCH 1/2] Add a strictatime mount option

Matthew Garrett
2009-03-26T17:50:45Z

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>
---
fs/namespace.c | 6 +++++-
include/linux/fs.h | 1 +
include/linux/mount.h | 1 +
3 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 06f8e63..d0659ec 100644
--- 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
--- 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
--- 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 */

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