[Devel] [PATCH v3 3/7] SUNRPC: send notification events on pipefs sb creation and destruction

[Stanislav Kinsbursky]

They will be used to notify subscribers about pipefs superblock creation and
destruction.
Subcribers will have to create their dentries on passed superblock on mount
event and destroy otherwise.

Signed-off-by: Stanislav Kinsbursky <skinsbur...@parallels.com>

---
 include/linux/sunrpc/rpc_pipe_fs.h |    8 ++++++++
 net/sunrpc/rpc_pipe.c              |   32 ++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/include/linux/sunrpc/rpc_pipe_fs.h 
b/include/linux/sunrpc/rpc_pipe_fs.h
index 08aae01..733ef50 100644
--- a/include/linux/sunrpc/rpc_pipe_fs.h
+++ b/include/linux/sunrpc/rpc_pipe_fs.h
@@ -43,6 +43,14 @@ RPC_I(struct inode *inode)
        return container_of(inode, struct rpc_inode, vfs_inode);
 }
 
+extern int rpc_pipefs_notifier_register(struct notifier_block *);
+extern void rpc_pipefs_notifier_unregister(struct notifier_block *);
+
+enum {
+       RPC_PIPEFS_MOUNT,
+       RPC_PIPEFS_UMOUNT,
+};
+
 extern ssize_t rpc_pipe_generic_upcall(struct file *, struct rpc_pipe_msg *,
                                       char __user *, size_t);
 extern int rpc_queue_upcall(struct inode *, struct rpc_pipe_msg *);
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index ff41fef..07fb7dd 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -28,8 +28,10 @@
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/sunrpc/cache.h>
 #include <linux/nsproxy.h>
+#include <linux/notifier.h>
 
 #include "netns.h"
+#include "sunrpc.h"
 
 static struct vfsmount *rpc_mnt __read_mostly;
 static int rpc_mount_count;
@@ -41,6 +43,20 @@ static struct kmem_cache *rpc_inode_cachep __read_mostly;
 
 #define RPC_UPCALL_TIMEOUT (30*HZ)
 
+static BLOCKING_NOTIFIER_HEAD(rpc_pipefs_notifier_list);
+
+int rpc_pipefs_notifier_register(struct notifier_block *nb)
+{
+       return blocking_notifier_chain_cond_register(&rpc_pipefs_notifier_list, 
nb);
+}
+EXPORT_SYMBOL_GPL(rpc_pipefs_notifier_register);
+
+void rpc_pipefs_notifier_unregister(struct notifier_block *nb)
+{
+       blocking_notifier_chain_unregister(&rpc_pipefs_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(rpc_pipefs_notifier_unregister);
+
 static void rpc_purge_list(struct rpc_inode *rpci, struct list_head *head,
                void (*destroy_msg)(struct rpc_pipe_msg *), int err)
 {
@@ -998,6 +1014,7 @@ rpc_fill_super(struct super_block *sb, void *data, int 
silent)
        struct inode *inode;
        struct dentry *root;
        struct net *net = data;
+       int err;
 
        sb->s_blocksize = PAGE_CACHE_SIZE;
        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
@@ -1015,8 +1032,20 @@ rpc_fill_super(struct super_block *sb, void *data, int 
silent)
        }
        if (rpc_populate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF, NULL))
                return -ENOMEM;
+       err = blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
+                                          RPC_PIPEFS_MOUNT,
+                                          sb);
+       if (err)
+               goto err_depopulate;
        sb->s_fs_info = get_net(net);
        return 0;
+
+err_depopulate:
+       blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
+                                          RPC_PIPEFS_UMOUNT,
+                                          sb);
+       __rpc_depopulate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF);
+       return err;
 }
 
 static struct dentry *
@@ -1031,6 +1060,9 @@ void rpc_kill_sb(struct super_block *sb)
        struct net *net = sb->s_fs_info;
 
        put_net(net);
+       blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
+                                          RPC_PIPEFS_UMOUNT,
+                                          sb);
        kill_litter_super(sb);
 }
 

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