take the targets of /proc/*/ns/* symlinks to separate fs
New pseudo-filesystem: nsfs. Targets of /proc/*/ns/* live there now.
It's not mountable (not even registered, so it's not in /proc/filesystems,
etc.). Files on it *are* bindable - we explicitly permit that in do_loopback().
This stuff lives in fs/nsfs.c now; proc_ns_fget() moved there as well.
get_proc_ns() is a macro now (it's simply returning ->i_private; would
have been an inline, if not for header ordering headache).
proc_ns_inode() is an ex-parrot. The interface used in procfs is
ns_get_path(path, task, ops) and ns_get_name(buf, size, task, ops).
Dentries and inodes are never hashed; a non-counting reference to dentry
is stashed in ns_common (removed by ->d_prune()) and reused by ns_get_path()
if present. See ns_get_path()/ns_prune_dentry/nsfs_evict() for details
of that mechanism.
As the result, proc_ns_follow_link() has stopped poking in nd->path.mnt;
it does nd_jump_link() on a consistent <vfsmount,dentry> pair it gets
from ns_get_path().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 77c6031..7d664ea 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -72,5 +72,6 @@
#define MTD_INODE_FS_MAGIC 0x11307854
#define ANON_INODE_FS_MAGIC 0x09041934
#define BTRFS_TEST_MAGIC 0x73727279
+#define NSFS_MAGIC 0x6e736673
#endif /* __LINUX_MAGIC_H__ */