afs: Support the AFS dynamic root

Support the AFS dynamic root which is a pseudo-volume that doesn't connect
to any server resource, but rather is just a root directory that
dynamically creates mountpoint directories where the name of such a
directory is the name of the cell.

Such a mount can be created thus:

	mount -t afs none /afs -o dyn

Dynamic root superblocks aren't shared except by bind mounts and
propagation.  Cell root volumes can then be mounted by referring to them by
name, e.g.:

	ls /afs/grand.central.org/
	ls /afs/.grand.central.org/

The kernel will upcall to consult the DNS if the address wasn't supplied
directly.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 30 insertions, 18 deletions

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index c7f17c44c7ce..6b39d0255b72 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -147,7 +147,7 @@ int afs_iget5_test(struct inode *inode, void *opaque)
  *
  * These pseudo inodes don't match anything.
  */
-static int afs_iget5_autocell_test(struct inode *inode, void *opaque)
+static int afs_iget5_pseudo_dir_test(struct inode *inode, void *opaque)
 {
 	return 0;
 }
@@ -169,31 +169,34 @@ static int afs_iget5_set(struct inode *inode, void *opaque)
 }
 
 /*
- * inode retrieval for autocell
+ * Create an inode for a dynamic root directory or an autocell dynamic
+ * automount dir.
  */
-struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,
-				int namesz, struct key *key)
+struct inode *afs_iget_pseudo_dir(struct super_block *sb, bool root)
 {
 	struct afs_iget_data data;
 	struct afs_super_info *as;
 	struct afs_vnode *vnode;
-	struct super_block *sb;
 	struct inode *inode;
 	static atomic_t afs_autocell_ino;
 
-	_enter("{%x:%u},%*.*s,",
-	       AFS_FS_I(dir)->fid.vid, AFS_FS_I(dir)->fid.vnode,
-	       namesz, namesz, dev_name ?: "");
+	_enter("");
 
-	sb = dir->i_sb;
 	as = sb->s_fs_info;
-	data.volume = as->volume;
-	data.fid.vid = as->volume->vid;
-	data.fid.unique = 0;
-	data.fid.vnode = 0;
+	if (as->volume) {
+		data.volume = as->volume;
+		data.fid.vid = as->volume->vid;
+	}
+	if (root) {
+		data.fid.vnode = 1;
+		data.fid.unique = 1;
+	} else {
+		data.fid.vnode = atomic_inc_return(&afs_autocell_ino);
+		data.fid.unique = 0;
+	}
 
-	inode = iget5_locked(sb, atomic_inc_return(&afs_autocell_ino),
-			     afs_iget5_autocell_test, afs_iget5_set,
+	inode = iget5_locked(sb, data.fid.vnode,
+			     afs_iget5_pseudo_dir_test, afs_iget5_set,
 			     &data);
 	if (!inode) {
 		_leave(" = -ENOMEM");
@@ -211,7 +214,12 @@ struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,
 
 	inode->i_size		= 0;
 	inode->i_mode		= S_IFDIR | S_IRUGO | S_IXUGO;
-	inode->i_op		= &afs_autocell_inode_operations;
+	if (root) {
+		inode->i_op	= &afs_dynroot_inode_operations;
+		inode->i_fop	= &afs_dynroot_file_operations;
+	} else {
+		inode->i_op	= &afs_autocell_inode_operations;
+	}
 	set_nlink(inode, 2);
 	inode->i_uid		= GLOBAL_ROOT_UID;
 	inode->i_gid		= GLOBAL_ROOT_GID;
@@ -223,8 +231,12 @@ struct inode *afs_iget_autocell(struct inode *dir, const char *dev_name,
 	inode->i_generation	= 0;
 
 	set_bit(AFS_VNODE_PSEUDODIR, &vnode->flags);
-	set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
-	inode->i_flags |= S_AUTOMOUNT | S_NOATIME;
+	if (!root) {
+		set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
+		inode->i_flags |= S_AUTOMOUNT;
+	}
+
+	inode->i_flags |= S_NOATIME;
 	unlock_new_inode(inode);
 	_leave(" = %p", inode);
 	return inode;