afs: Make /afs/.<cell> as well as /afs/<cell> mountpoints

When a cell is instantiated, automatically create an /afs/.<cell>
mountpoint to match the /afs/<cell> mountpoint to match other AFS clients.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20250107183454.608451-2-dhowells@redhat.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

2 files changed, 41 insertions, 24 deletions

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index caa09875f520..1aba6d4d03a9 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -146,18 +146,20 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 		return ERR_PTR(-ENOMEM);
 	}
 
-	cell->name = kmalloc(namelen + 1, GFP_KERNEL);
+	cell->name = kmalloc(1 + namelen + 1, GFP_KERNEL);
 	if (!cell->name) {
 		kfree(cell);
 		return ERR_PTR(-ENOMEM);
 	}
 
-	cell->net = net;
+	cell->name[0] = '.';
+	cell->name++;
 	cell->name_len = namelen;
 	for (i = 0; i < namelen; i++)
 		cell->name[i] = tolower(name[i]);
 	cell->name[i] = 0;
 
+	cell->net = net;
 	refcount_set(&cell->ref, 1);
 	atomic_set(&cell->active, 0);
 	INIT_WORK(&cell->manager, afs_manage_cell_work);
@@ -211,7 +213,7 @@ parse_failed:
 	if (ret == -EINVAL)
 		printk(KERN_ERR "kAFS: bad VL server IP address\n");
 error:
-	kfree(cell->name);
+	kfree(cell->name - 1);
 	kfree(cell);
 	_leave(" = %d", ret);
 	return ERR_PTR(ret);
@@ -502,7 +504,7 @@ static void afs_cell_destroy(struct rcu_head *rcu)
 	afs_put_vlserverlist(net, rcu_access_pointer(cell->vl_servers));
 	afs_unuse_cell(net, cell->alias_of, afs_cell_trace_unuse_alias);
 	key_put(cell->anonymous_key);
-	kfree(cell->name);
+	kfree(cell->name - 1);
 	kfree(cell);
 
 	afs_dec_cells_outstanding(net);
@@ -710,7 +712,8 @@ static void afs_deactivate_cell(struct afs_net *net, struct afs_cell *cell)
 	afs_proc_cell_remove(cell);
 
 	mutex_lock(&net->proc_cells_lock);
-	hlist_del_rcu(&cell->proc_link);
+	if (!hlist_unhashed(&cell->proc_link))
+		hlist_del_rcu(&cell->proc_link);
 	afs_dynroot_rmdir(net, cell);
 	mutex_unlock(&net->proc_cells_lock);
 
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
index c4d2711e20ad..f80a4244b9d2 100644
--- a/fs/afs/dynroot.c
+++ b/fs/afs/dynroot.c
@@ -271,7 +271,8 @@ const struct dentry_operations afs_dynroot_dentry_operations = {
 int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
 {
 	struct super_block *sb = net->dynroot_sb;
-	struct dentry *root, *subdir;
+	struct dentry *root, *subdir, *dsubdir;
+	char *dotname = cell->name - 1;
 	int ret;
 
 	if (!sb || atomic_read(&sb->s_active) == 0)
@@ -286,34 +287,31 @@ int afs_dynroot_mkdir(struct afs_net *net, struct afs_cell *cell)
 		goto unlock;
 	}
 
-	/* Note that we're retaining an extra ref on the dentry */
+	dsubdir = lookup_one_len(dotname, root, cell->name_len + 1);
+	if (IS_ERR(dsubdir)) {
+		ret = PTR_ERR(dsubdir);
+		dput(subdir);
+		goto unlock;
+	}
+
+	/* Note that we're retaining extra refs on the dentries. */
 	subdir->d_fsdata = (void *)1UL;
+	dsubdir->d_fsdata = (void *)1UL;
 	ret = 0;
 unlock:
 	inode_unlock(root->d_inode);
 	return ret;
 }
 
-/*
- * Remove a manually added cell mount directory.
- * - The caller must hold net->proc_cells_lock
- */
-void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
+static void afs_dynroot_rm_one_dir(struct dentry *root, const char *name, size_t name_len)
 {
-	struct super_block *sb = net->dynroot_sb;
-	struct dentry *root, *subdir;
-
-	if (!sb || atomic_read(&sb->s_active) == 0)
-		return;
-
-	root = sb->s_root;
-	inode_lock(root->d_inode);
+	struct dentry *subdir;
 
 	/* Don't want to trigger a lookup call, which will re-add the cell */
-	subdir = try_lookup_one_len(cell->name, root, cell->name_len);
+	subdir = try_lookup_one_len(name, root, name_len);
 	if (IS_ERR_OR_NULL(subdir)) {
 		_debug("lookup %ld", PTR_ERR(subdir));
-		goto no_dentry;
+		return;
 	}
 
 	_debug("rmdir %pd %u", subdir, d_count(subdir));
@@ -324,8 +322,24 @@ void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
 		dput(subdir);
 	}
 	dput(subdir);
-no_dentry:
-	inode_unlock(root->d_inode);
+}
+
+/*
+ * Remove a manually added cell mount directory.
+ * - The caller must hold net->proc_cells_lock
+ */
+void afs_dynroot_rmdir(struct afs_net *net, struct afs_cell *cell)
+{
+	struct super_block *sb = net->dynroot_sb;
+	char *dotname = cell->name - 1;
+
+	if (!sb || atomic_read(&sb->s_active) == 0)
+		return;
+
+	inode_lock(sb->s_root->d_inode);
+	afs_dynroot_rm_one_dir(sb->s_root, cell->name, cell->name_len);
+	afs_dynroot_rm_one_dir(sb->s_root, dotname, cell->name_len + 1);
+	inode_unlock(sb->s_root->d_inode);
 	_leave("");
 }