[PATCH 16/32] union-mount: Introduce MNT_UNION and MS_UNION flags

From: Jan Blunck
Date: Mon May 18 2009 - 12:14:38 EST


Add per mountpoint flag for Union Mount support. You need additional patches
to util-linux for that to work - see:

git://git.kernel.org/pub/scm/utils/util-linux-ng/val/util-linux-ng.git

Signed-off-by: Jan Blunck <jblunck@xxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: Valerie Aurora (Henson) <vaurora@xxxxxxxxxx>
---
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 f0a5ce7..53998f2 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_UNION, ",union" },
{ 0, NULL }
};
const struct proc_fs_info *fs_infop;
@@ -1934,9 +1935,12 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
mnt_flags |= MNT_RELATIME;
if (flags & MS_RDONLY)
mnt_flags |= MNT_READONLY;
+ if (flags & MS_UNION)
+ mnt_flags |= MNT_UNION;

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_UNION);

/* ... 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 f5ca398..7f07768 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -125,6 +125,7 @@ struct inodes_stat_t {
#define MS_REMOUNT 32 /* Alter flags of a mounted FS */
#define MS_MANDLOCK 64 /* Allow mandatory locks on an FS */
#define MS_DIRSYNC 128 /* Directory modifications are synchronous */
+#define MS_UNION 256
#define MS_NOATIME 1024 /* Do not update access times. */
#define MS_NODIRATIME 2048 /* Do not update directory access times */
#define MS_BIND 4096
diff --git a/include/linux/mount.h b/include/linux/mount.h
index cab2a85..bd35fb8 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -34,6 +34,7 @@ struct mnt_namespace;
#define MNT_SHARED 0x1000 /* if the vfsmount is a shared mount */
#define MNT_UNBINDABLE 0x2000 /* if the vfsmount is a unbindable mount */
#define MNT_PNODE_MASK 0x3000 /* propagation flag mask */
+#define MNT_UNION 0x4000 /* if the vfsmount is a union mount */

struct vfsmount {
struct list_head mnt_hash;
--
1.6.1.3

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