AFS: Implement an autocell mount capability [ver #2]

Implement the ability for the root directory of a mounted AFS filesystem to
accept lookups of arbitrary directory names, to interpet the names as the names
of cells, to look the cell names up in the DNS for AFSDB records and to mount
the root.cell volume of the nominated cell on the pseudo-directory created by
lookup.

This facility is requested by passing:

	-o autocell

to the mountpoint for which this is desired, usually the /afs mount.

To use this facility, a DNS upcall program is required for AFSDB records.  This
can be obtained from:

	http://people.redhat.com/~dhowells/afs/dns.afsdb.c

It should be compiled with -lresolv and -lkeyutils and installed as, say:

	/usr/sbin/dns.afsdb

Then the following line needs to be added to /sbin/request-key.conf:

	create	dns_resolver afsdb:*	*	/usr/sbin/dns.afsdb %k

This can be tested by mounting AFS, say:

	insmod dns_resolver.ko
	insmod af-rxrpc.ko
	insmod kafs.ko rootcell=grand.central.org
	mount -t afs "#grand.central.org:root.cell." /afs -o autocell

and doing:

	ls /afs/grand.central.org/

which should show:

	archive/  cvs/  doc/  local/  project/  service/  software/  user/  www/

if it works.

Signed-off-by: Wang Lei <wang840925@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 45 insertions, 2 deletions

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index b42d5cc1d6d2..0d38c09bd55e 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -477,6 +477,40 @@ static int afs_do_lookup(struct inode *dir, struct dentry *dentry,
 }
 
 /*
+ * Try to auto mount the mountpoint with pseudo directory, if the autocell
+ * operation is setted.
+ */
+static struct inode *afs_try_auto_mntpt(
+        int ret, struct dentry *dentry, struct inode *dir, struct key *key,
+        struct afs_fid *fid)
+{
+        const char *devname = dentry->d_name.name;
+        struct afs_vnode *vnode = AFS_FS_I(dir);
+        struct inode *inode;
+
+        _enter("%d, %p{%s}, {%x:%u}, %p",
+               ret, dentry, devname, vnode->fid.vid, vnode->fid.vnode, key);
+
+        if (ret != -ENOENT ||
+            !test_bit(AFS_VNODE_AUTOCELL, &vnode->flags))
+                goto out;
+
+        inode = afs_iget_autocell(dir, devname, strlen(devname), key);
+        if (IS_ERR(inode)) {
+                ret = PTR_ERR(inode);
+                goto out;
+        }
+
+        *fid = AFS_FS_I(inode)->fid;
+        _leave("= %p", inode);
+        return inode;
+
+out:
+        _leave("= %d", ret);
+        return ERR_PTR(ret);
+}
+
+/*
  * look up an entry in a directory
  */
 static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
@@ -520,6 +554,13 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
 
         ret = afs_do_lookup(dir, dentry, &fid, key);
         if (ret < 0) {
+                inode = afs_try_auto_mntpt(ret, dentry, dir, key, &fid);
+                if (!IS_ERR(inode)) {
+                        key_put(key);
+                        goto success;
+                }
+
+                ret = PTR_ERR(inode);
                 key_put(key);
                 if (ret == -ENOENT) {
                         d_add(dentry, NULL);
@@ -539,6 +580,7 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
                 return ERR_CAST(inode);
         }
 
+success:
         dentry->d_op = &afs_fs_dentry_operations;
 
         d_add(dentry, inode);
@@ -696,8 +738,9 @@ static int afs_d_delete(struct dentry *dentry)
                 goto zap;
 
         if (dentry->d_inode &&
-            test_bit(AFS_VNODE_DELETED, &AFS_FS_I(dentry->d_inode)->flags))
-                        goto zap;
+            (test_bit(AFS_VNODE_DELETED,   &AFS_FS_I(dentry->d_inode)->flags) ||
+             test_bit(AFS_VNODE_PSEUDODIR, &AFS_FS_I(dentry->d_inode)->flags)))
+                goto zap;
 
         _leave(" = 0 [keep]");
         return 0;