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pid namespaces: introduce MS_KERNMOUNT flag 

This flag tells the .get_sb callback that this is a kern_mount() call so that
it can trust *data pointer to be valid in-kernel one.  If this flag is passed
from the user process, it is cleared since the *data pointer is not a valid
kernel object.

Running a few steps forward - this will be needed for proc to create the
superblock and store a valid pid namespace on it during the namespace
creation.  The reason, why the namespace cannot live without proc mount is
described in the appropriate patch.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pavel Emelyanov 2007-10-18 23:40:02 -07:00 committed by Linus Torvalds
parent 2e4a707269
commit 8bf9725c29
3 changed files with 7 additions and 5 deletions
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2
fs/namespace.c
View File

@ -1411,7 +1411,7 @@ long do_mount(char *dev_name, char *dir_name, char *type_page,
mnt_flags |= MNT_RELATIME;
flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
MS_NOATIME | MS_NODIRATIME | MS_RELATIME);
MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT);
/* ... and get the mountpoint */
retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);

6
fs/super.c
View File

@ -944,9 +944,9 @@ do_kern_mount(const char *fstype, int flags, const char *name, void *data)
return mnt;
}
struct vfsmount *kern_mount(struct file_system_type *type)
struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
{
return vfs_kern_mount(type, 0, type->name, NULL);
return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
}
EXPORT_SYMBOL(kern_mount);
EXPORT_SYMBOL_GPL(kern_mount_data);

4
include/linux/fs.h
View File

@ -123,6 +123,7 @@ extern int dir_notify_enable;
#define MS_SLAVE (1<<19) /* change to slave */
#define MS_SHARED (1<<20) /* change to shared */
#define MS_RELATIME (1<<21) /* Update atime relative to mtime/ctime. */
#define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */
#define MS_ACTIVE (1<<30)
#define MS_NOUSER (1<<31)
@ -1459,7 +1460,8 @@ void unnamed_dev_init(void);
extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);
extern struct vfsmount *kern_mount(struct file_system_type *);
extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data);
#define kern_mount(type) kern_mount_data(type, NULL)
extern int may_umount_tree(struct vfsmount *);
extern int may_umount(struct vfsmount *);
extern void umount_tree(struct vfsmount *, int, struct list_head *);