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, 16 insertions, 4 deletions

diff --git a/fs/afs/super.c b/fs/afs/super.c
index 9cf80f02da1..77e1e5a6115 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -16,6 +16,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/mount.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/smp_lock.h>
@@ -48,6 +49,7 @@ struct file_system_type afs_fs_type = {
 static const struct super_operations afs_super_ops = {
         .statfs         = afs_statfs,
         .alloc_inode    = afs_alloc_inode,
+        .drop_inode     = afs_drop_inode,
         .destroy_inode  = afs_destroy_inode,
         .evict_inode    = afs_evict_inode,
         .put_super      = afs_put_super,
@@ -62,12 +64,14 @@ enum {
         afs_opt_cell,
         afs_opt_rwpath,
         afs_opt_vol,
+        afs_opt_autocell,
 };
 
 static const match_table_t afs_options_list = {
         { afs_opt_cell,         "cell=%s"       },
         { afs_opt_rwpath,       "rwpath"        },
         { afs_opt_vol,          "vol=%s"        },
+        { afs_opt_autocell,     "autocell"      },
         { afs_no_opt,           NULL            },
 };
 
@@ -151,7 +155,8 @@ static int afs_parse_options(struct afs_mount_params *params,
                 switch (token) {
                 case afs_opt_cell:
                         cell = afs_cell_lookup(args[0].from,
-                                               args[0].to - args[0].from);
+                                               args[0].to - args[0].from,
+                                               false);
                         if (IS_ERR(cell))
                                 return PTR_ERR(cell);
                         afs_put_cell(params->cell);
@@ -166,6 +171,10 @@ static int afs_parse_options(struct afs_mount_params *params,
                         *devname = args[0].from;
                         break;
 
+                case afs_opt_autocell:
+                        params->autocell = 1;
+                        break;
+
                 default:
                         printk(KERN_ERR "kAFS:"
                                " Unknown or invalid mount option: '%s'\n", p);
@@ -252,10 +261,10 @@ static int afs_parse_device_name(struct afs_mount_params *params,
 
         /* lookup the cell record */
         if (cellname || !params->cell) {
-                cell = afs_cell_lookup(cellname, cellnamesz);
+                cell = afs_cell_lookup(cellname, cellnamesz, true);
                 if (IS_ERR(cell)) {
-                        printk(KERN_ERR "kAFS: unable to lookup cell '%s'\n",
-                               cellname ?: "");
+                        printk(KERN_ERR "kAFS: unable to lookup cell '%*.*s'\n",
+                               cellnamesz, cellnamesz, cellname ?: "");
                         return PTR_ERR(cell);
                 }
                 afs_put_cell(params->cell);
@@ -321,6 +330,9 @@ static int afs_fill_super(struct super_block *sb, void *data)
         if (IS_ERR(inode))
                 goto error_inode;
 
+        if (params->autocell)
+                set_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(inode)->flags);
+
         ret = -ENOMEM;
         root = d_alloc_root(inode);
         if (!root)