rxrpc: Don't expose skbs to in-kernel users [ver #2]

Don't expose skbs to in-kernel users, such as the AFS filesystem, but
instead provide a notification hook the indicates that a call needs
attention and another that indicates that there's a new call to be
collected.

This makes the following possibilities more achievable:

 (1) Call refcounting can be made simpler if skbs don't hold refs to calls.

 (2) skbs referring to non-data events will be able to be freed much sooner
     rather than being queued for AFS to pick up as rxrpc_kernel_recv_data
     will be able to consult the call state.

 (3) We can shortcut the receive phase when a call is remotely aborted
     because we don't have to go through all the packets to get to the one
     cancelling the operation.

 (4) It makes it easier to do encryption/decryption directly between AFS's
     buffers and sk_buffs.

 (5) Encryption/decryption can more easily be done in the AFS's thread
     contexts - usually that of the userspace process that issued a syscall
     - rather than in one of rxrpc's background threads on a workqueue.

 (6) AFS will be able to wait synchronously on a call inside AF_RXRPC.

To make this work, the following interface function has been added:

     int rxrpc_kernel_recv_data(
		struct socket *sock, struct rxrpc_call *call,
		void *buffer, size_t bufsize, size_t *_offset,
		bool want_more, u32 *_abort_code);

This is the recvmsg equivalent.  It allows the caller to find out about the
state of a specific call and to transfer received data into a buffer
piecemeal.

afs_extract_data() and rxrpc_kernel_recv_data() now do all the extraction
logic between them.  They don't wait synchronously yet because the socket
lock needs to be dealt with.

Five interface functions have been removed:

	rxrpc_kernel_is_data_last()
    	rxrpc_kernel_get_abort_code()
    	rxrpc_kernel_get_error_number()
    	rxrpc_kernel_free_skb()
    	rxrpc_kernel_data_consumed()

As a temporary hack, sk_buffs going to an in-kernel call are queued on the
rxrpc_call struct (->knlrecv_queue) rather than being handed over to the
in-kernel user.  To process the queue internally, a temporary function,
temp_deliver_data() has been added.  This will be replaced with common code
between the rxrpc_recvmsg() path and the kernel_rxrpc_recv_data() path in a
future patch.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 24 deletions

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index d97552d..5497c84 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -13,7 +13,6 @@
 #include <linux/kernel.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
-#include <linux/skbuff.h>
 #include <linux/rxrpc.h>
 #include <linux/key.h>
 #include <linux/workqueue.h>
@@ -57,7 +56,7 @@ struct afs_mount_params {
  */
 struct afs_wait_mode {
 	/* RxRPC received message notification */
-	void (*rx_wakeup)(struct afs_call *call);
+	rxrpc_notify_rx_t notify_rx;
 
 	/* synchronous call waiter and call dispatched notification */
 	int (*wait)(struct afs_call *call);
@@ -76,10 +75,8 @@ struct afs_call {
 	const struct afs_call_type *type;	/* type of call */
 	const struct afs_wait_mode *wait_mode;	/* completion wait mode */
 	wait_queue_head_t	waitq;		/* processes awaiting completion */
-	void (*async_workfn)(struct afs_call *call); /* asynchronous work function */
 	struct work_struct	async_work;	/* asynchronous work processor */
 	struct work_struct	work;		/* actual work processor */
-	struct sk_buff_head	rx_queue;	/* received packets */
 	struct rxrpc_call	*rxcall;	/* RxRPC call handle */
 	struct key		*key;		/* security for this call */
 	struct afs_server	*server;	/* server affected by incoming CM call */
@@ -93,6 +90,7 @@ struct afs_call {
 	void			*reply4;	/* reply buffer (fourth part) */
 	pgoff_t			first;		/* first page in mapping to deal with */
 	pgoff_t			last;		/* last page in mapping to deal with */
+	size_t			offset;		/* offset into received data store */
 	enum {					/* call state */
 		AFS_CALL_REQUESTING,	/* request is being sent for outgoing call */
 		AFS_CALL_AWAIT_REPLY,	/* awaiting reply to outgoing call */
@@ -100,21 +98,18 @@ struct afs_call {
 		AFS_CALL_AWAIT_REQUEST,	/* awaiting request data on incoming call */
 		AFS_CALL_REPLYING,	/* replying to incoming call */
 		AFS_CALL_AWAIT_ACK,	/* awaiting final ACK of incoming call */
-		AFS_CALL_COMPLETE,	/* successfully completed */
-		AFS_CALL_BUSY,		/* server was busy */
-		AFS_CALL_ABORTED,	/* call was aborted */
-		AFS_CALL_ERROR,		/* call failed due to error */
+		AFS_CALL_COMPLETE,	/* Completed or failed */
 	}			state;
 	int			error;		/* error code */
+	u32			abort_code;	/* Remote abort ID or 0 */
 	unsigned		request_size;	/* size of request data */
 	unsigned		reply_max;	/* maximum size of reply */
-	unsigned		reply_size;	/* current size of reply */
 	unsigned		first_offset;	/* offset into mapping[first] */
 	unsigned		last_to;	/* amount of mapping[last] */
-	unsigned		offset;		/* offset into received data store */
 	unsigned char		unmarshall;	/* unmarshalling phase */
 	bool			incoming;	/* T if incoming call */
 	bool			send_pages;	/* T if data from mapping should be sent */
+	bool			need_attention;	/* T if RxRPC poked us */
 	u16			service_id;	/* RxRPC service ID to call */
 	__be16			port;		/* target UDP port */
 	__be32			operation_ID;	/* operation ID for an incoming call */
@@ -129,8 +124,7 @@ struct afs_call_type {
 	/* deliver request or reply data to an call
 	 * - returning an error will cause the call to be aborted
 	 */
-	int (*deliver)(struct afs_call *call, struct sk_buff *skb,
-		       bool last);
+	int (*deliver)(struct afs_call *call);
 
 	/* map an abort code to an error number */
 	int (*abort_to_error)(u32 abort_code);
@@ -612,27 +606,18 @@ extern struct socket *afs_socket;
 
 extern int afs_open_socket(void);
 extern void afs_close_socket(void);
-extern void afs_data_consumed(struct afs_call *, struct sk_buff *);
 extern int afs_make_call(struct in_addr *, struct afs_call *, gfp_t,
 			 const struct afs_wait_mode *);
 extern struct afs_call *afs_alloc_flat_call(const struct afs_call_type *,
 					    size_t, size_t);
 extern void afs_flat_call_destructor(struct afs_call *);
-extern int afs_transfer_reply(struct afs_call *, struct sk_buff *, bool);
 extern void afs_send_empty_reply(struct afs_call *);
 extern void afs_send_simple_reply(struct afs_call *, const void *, size_t);
-extern int afs_extract_data(struct afs_call *, struct sk_buff *, bool, void *,
-			    size_t);
+extern int afs_extract_data(struct afs_call *, void *, size_t, bool);
 
-static inline int afs_data_complete(struct afs_call *call, struct sk_buff *skb,
-				    bool last)
+static inline int afs_transfer_reply(struct afs_call *call)
 {
-	if (skb->len > 0)
-		return -EBADMSG;
-	afs_data_consumed(call, skb);
-	if (!last)
-		return -EAGAIN;
-	return 0;
+	return afs_extract_data(call, call->buffer, call->reply_max, false);
 }
 
 /*