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From: Valerie Aurora on 6 Aug 2010 18:40
From: Jan Blunck <jblunck(a)suse.de>

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(a)suse.de>
Signed-off-by: Valerie Aurora <vaurora(a)redhat.com>
---
fs/namespace.c | 5 ++++-
include/linux/fs.h | 1 +
include/linux/mount.h | 4 ++--
3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 984c331..f115cb6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -809,6 +809,7 @@ static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
{ MNT_NODIRATIME, ",nodiratime" },
{ MNT_RELATIME, ",relatime" },
{ MNT_STRICTATIME, ",strictatime" },
+ { MNT_UNION, ",union" },
{ 0, NULL }
};
const struct proc_fs_info *fs_infop;
@@ -2008,10 +2009,12 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
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_STRICTATIME);
+ MS_STRICTATIME | MS_UNION);

if (flags & MS_REMOUNT)
retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 71ee74e..31cfa48 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -192,6 +192,7 @@ 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 /* Merge namespace with FS mounted below */
#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 4bd0547..0302703 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -43,9 +43,9 @@ struct mnt_namespace;
*/
#define MNT_SHARED_MASK (MNT_UNBINDABLE)
#define MNT_PROPAGATION_MASK (MNT_SHARED | MNT_UNBINDABLE)
+#define MNT_UNION 0x4000 /* top layer of a union mount */

-
-#define MNT_INTERNAL 0x4000
+#define MNT_INTERNAL 0x8000

struct vfsmount {
struct list_head mnt_hash;
--
1.6.3.3

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Prev: [PATCH 37/38] union-mount: Implement union-aware setxattr()
Next: [PATCH 03/38] VFS: Add read-only users count to superblock