Add the infrastructure to support a generic nocmtime mount flag. Like
MS_NOATIME/MNT_NOATIME this can be used to support the mount option in
file systems without having to touch each file system.
This will be used to provide a priviledged indication that unpriviledged
apps can safely use O_NOCMTIME to prevent cmtime updates without harm.
Signed-off-by: Zach Brown <zab@xxxxxxxxx>
---
fs/namespace.c | 2 ++
fs/proc_namespace.c | 1 +
fs/statfs.c | 2 ++
include/linux/mount.h | 1 +
include/linux/statfs.h | 1 +
include/uapi/linux/fs.h | 1 +
6 files changed, 8 insertions(+)
diff --git a/fs/namespace.c b/fs/namespace.c
index 1b9e111..48be1f9 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2652,6 +2652,8 @@ long do_mount(const char *dev_name, const char __user *dir_name,
mnt_flags |= MNT_NOEXEC;
if (flags & MS_NOATIME)
mnt_flags |= MNT_NOATIME;
+ if (flags & MS_NOCMTIME)
+ mnt_flags |= MNT_NOCMTIME;
if (flags & MS_NODIRATIME)
mnt_flags |= MNT_NODIRATIME;
if (flags & MS_STRICTATIME)
diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 8db932d..49d7839 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -64,6 +64,7 @@ static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
{ MNT_NODEV, ",nodev" },
{ MNT_NOEXEC, ",noexec" },
{ MNT_NOATIME, ",noatime" },
+ { MNT_NOCMTIME, ",nocmtime" },
{ MNT_NODIRATIME, ",nodiratime" },
{ MNT_RELATIME, ",relatime" },
{ 0, NULL }
diff --git a/fs/statfs.c b/fs/statfs.c
index 083dc0a..43d3de2 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c
@@ -23,6 +23,8 @@ static int flags_by_mnt(int mnt_flags)
flags |= ST_NOEXEC;
if (mnt_flags & MNT_NOATIME)
flags |= ST_NOATIME;
+ if (mnt_flags & MNT_NOCMTIME)
+ flags |= ST_NOCMTIME;
if (mnt_flags & MNT_NODIRATIME)
flags |= ST_NODIRATIME;
if (mnt_flags & MNT_RELATIME)
diff --git a/include/linux/mount.h b/include/linux/mount.h
index f822c3c..deb458f 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -28,6 +28,7 @@ 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_NOCMTIME 0x80 /* allow O_NOCMTIME to stop cmtime updates */
#define MNT_SHRINKABLE 0x100
#define MNT_WRITE_HOLD 0x200
diff --git a/include/linux/statfs.h b/include/linux/statfs.h
index 0166d32..bde224e 100644
--- a/include/linux/statfs.h
+++ b/include/linux/statfs.h
@@ -39,5 +39,6 @@ struct kstatfs {
#define ST_NOATIME 0x0400 /* do not update access times */
#define ST_NODIRATIME 0x0800 /* do not update directory access times */
#define ST_RELATIME 0x1000 /* update atime relative to mtime/ctime */
+#define ST_NOCMTIME 0x2000 /* allow O_NOCMTIME to stop cmtime updates */
#endif
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 9b964a5..af1131e 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -91,6 +91,7 @@ struct inodes_stat_t {
#define MS_I_VERSION (1<<23) /* Update inode I_version field */
#define MS_STRICTATIME (1<<24) /* Always perform atime updates */
#define MS_LAZYTIME (1<<25) /* Update the on-disk [acm]times lazily */
+#define MS_NOCMTIME (1<<26) /* allow O_NOCMTIME to stop cmtime updates */
/* These sb flags are internal to the kernel */
#define MS_NOSEC (1<<28)
--
2.1.0
--
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