From 57afb87224d7ff5426da80dad9b1b0bd3859b7d4 Mon Sep 17 00:00:00 2001 From: Zach Brown Date: Fri, 15 May 2015 14:23:47 -0700 Subject: [PATCH] vfs: add generic nocmtime mount flag 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 --- 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 1b9e11167bae..48be1f9ec2a7 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 8db932da4009..49d78396be2d 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 083dc0ac9140..43d3de25ebb7 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 f822c3c11377..deb458f1cfc3 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 0166d320a75d..bde224e35f58 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 9b964a5920af..af1131e0cbda 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) -- 2.47.3