[PATCH v3 09/16] sunrpc: introduce rpc_pipefs_add_destroy_cb()

["Kirill A. Shutemov" <kas@openvz.org>]

Add facility to do some action on destroying of rpc_pipefs superblock.

Signed-off-by: Kirill A. Shutemov <kas@openvz.org>
---
 include/linux/sunrpc/rpc_pipe_fs.h |    3 ++
 net/sunrpc/rpc_pipe.c              |   51 ++++++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/include/linux/sunrpc/rpc_pipe_fs.h b/include/linux/sunrpc/rpc_pipe_fs.h
index b09bfa5..f5216f1 100644
--- a/include/linux/sunrpc/rpc_pipe_fs.h
+++ b/include/linux/sunrpc/rpc_pipe_fs.h
@@ -46,6 +46,9 @@ RPC_I(struct inode *inode)
 
 extern struct vfsmount *init_rpc_pipefs;
 
+extern int rpc_pipefs_add_destroy_cb(struct super_block *sb,
+		void (*destroy_cb)(void *data), void *data);
+
 extern int rpc_queue_upcall(struct inode *, struct rpc_pipe_msg *);
 
 struct rpc_clnt;
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index 484c9a3..39511e3 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -939,6 +939,31 @@ static const struct super_operations s_ops = {
 
 #define RPCAUTH_GSSMAGIC 0x67596969
 
+struct destroy_cb {
+	struct list_head list;
+	void (*callback)(void *data);
+	void *data;
+};
+
+int rpc_pipefs_add_destroy_cb(struct super_block *sb,
+		void (*destroy_cb)(void *data), void *data)
+{
+	struct destroy_cb *dcb;
+	struct list_head *destroy_cb_list = sb->s_fs_info;
+
+	dcb = kmalloc(sizeof(*dcb), GFP_KERNEL);
+	if (!dcb)
+		return -ENOMEM;
+
+	dcb->callback = destroy_cb;
+	dcb->data = data;
+	INIT_LIST_HEAD(&dcb->list);
+	list_add(&dcb->list, destroy_cb_list);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rpc_pipefs_add_destroy_cb);
+
 /*
  * We have a single directory with 1 node in it.
  */
@@ -1004,8 +1029,16 @@ rpc_fill_super(struct super_block *sb, void *data, int silent)
 		iput(inode);
 		return -ENOMEM;
 	}
-	if (rpc_populate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF, NULL))
+	/* List of destroy callbacks */
+	sb->s_fs_info = kmalloc(sizeof(struct list_head), GFP_KERNEL);
+	if (!sb->s_fs_info)
+		return -ENOMEM;
+	INIT_LIST_HEAD((struct list_head*) &sb->s_fs_info);
+	if (rpc_populate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF, NULL)) {
+		kfree(sb->s_fs_info);
 		return -ENOMEM;
+	}
+
 	return 0;
 }
 
@@ -1016,11 +1049,25 @@ rpc_mount(struct file_system_type *fs_type,
 	return mount_single(fs_type, flags, data, rpc_fill_super);
 }
 
+static void rpc_kill_sb(struct super_block *sb)
+{
+	struct list_head *destroy_cb_list = sb->s_fs_info;
+	struct destroy_cb *dcb, *tmp;
+
+	list_for_each_entry_safe(dcb, tmp, destroy_cb_list, list) {
+		dcb->callback(dcb->data);
+		list_del(&dcb->list);
+		kfree(dcb);
+	}
+	kfree(destroy_cb_list);
+	kill_litter_super(sb);
+}
+
 static struct file_system_type rpc_pipe_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "rpc_pipefs",
 	.mount		= rpc_mount,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= rpc_kill_sb,
 };
 
 static void
-- 
1.7.3.4