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, 62 insertions, 86 deletions

diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 9312b92e54be..96f4d764d1a6 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -235,16 +235,15 @@ static void xdr_decode_AFSFetchVolumeStatus(const __be32 **_bp,
 /*
  * deliver reply data to an FS.FetchStatus
  */
-static int afs_deliver_fs_fetch_status(struct afs_call *call,
-				       struct sk_buff *skb, bool last)
+static int afs_deliver_fs_fetch_status(struct afs_call *call)
 {
 	struct afs_vnode *vnode = call->reply;
 	const __be32 *bp;
 	int ret;
 
-	_enter(",,%u", last);
+	_enter("");
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -307,8 +306,7 @@ int afs_fs_fetch_file_status(struct afs_server *server,
 /*
  * deliver reply data to an FS.FetchData
  */
-static int afs_deliver_fs_fetch_data(struct afs_call *call,
-				     struct sk_buff *skb, bool last)
+static int afs_deliver_fs_fetch_data(struct afs_call *call)
 {
 	struct afs_vnode *vnode = call->reply;
 	const __be32 *bp;
@@ -316,7 +314,7 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call,
 	void *buffer;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
 	switch (call->unmarshall) {
 	case 0:
@@ -332,7 +330,7 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call,
 		 * client) */
 	case 1:
 		_debug("extract data length (MSW)");
-		ret = afs_extract_data(call, skb, last, &call->tmp, 4);
+		ret = afs_extract_data(call, &call->tmp, 4, true);
 		if (ret < 0)
 			return ret;
 
@@ -347,7 +345,7 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call,
 		/* extract the returned data length */
 	case 2:
 		_debug("extract data length");
-		ret = afs_extract_data(call, skb, last, &call->tmp, 4);
+		ret = afs_extract_data(call, &call->tmp, 4, true);
 		if (ret < 0)
 			return ret;
 
@@ -363,10 +361,10 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call,
 		_debug("extract data");
 		if (call->count > 0) {
 			page = call->reply3;
-			buffer = kmap_atomic(page);
-			ret = afs_extract_data(call, skb, last, buffer,
-					       call->count);
-			kunmap_atomic(buffer);
+			buffer = kmap(page);
+			ret = afs_extract_data(call, buffer,
+					       call->count, true);
+			kunmap(buffer);
 			if (ret < 0)
 				return ret;
 		}
@@ -376,8 +374,8 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call,
 
 		/* extract the metadata */
 	case 4:
-		ret = afs_extract_data(call, skb, last, call->buffer,
-				       (21 + 3 + 6) * 4);
+		ret = afs_extract_data(call, call->buffer,
+				       (21 + 3 + 6) * 4, false);
 		if (ret < 0)
 			return ret;
 
@@ -391,18 +389,15 @@ static int afs_deliver_fs_fetch_data(struct afs_call *call,
 		call->unmarshall++;
 
 	case 5:
-		ret = afs_data_complete(call, skb, last);
-		if (ret < 0)
-			return ret;
 		break;
 	}
 
 	if (call->count < PAGE_SIZE) {
 		_debug("clear");
 		page = call->reply3;
-		buffer = kmap_atomic(page);
+		buffer = kmap(page);
 		memset(buffer + call->count, 0, PAGE_SIZE - call->count);
-		kunmap_atomic(buffer);
+		kunmap(buffer);
 	}
 
 	_leave(" = 0 [done]");
@@ -515,13 +510,12 @@ int afs_fs_fetch_data(struct afs_server *server,
 /*
  * deliver reply data to an FS.GiveUpCallBacks
  */
-static int afs_deliver_fs_give_up_callbacks(struct afs_call *call,
-					    struct sk_buff *skb, bool last)
+static int afs_deliver_fs_give_up_callbacks(struct afs_call *call)
 {
-	_enter(",{%u},%d", skb->len, last);
+	_enter("");
 
 	/* shouldn't be any reply data */
-	return afs_data_complete(call, skb, last);
+	return afs_extract_data(call, NULL, 0, false);
 }
 
 /*
@@ -599,16 +593,15 @@ int afs_fs_give_up_callbacks(struct afs_server *server,
 /*
  * deliver reply data to an FS.CreateFile or an FS.MakeDir
  */
-static int afs_deliver_fs_create_vnode(struct afs_call *call,
-				       struct sk_buff *skb, bool last)
+static int afs_deliver_fs_create_vnode(struct afs_call *call)
 {
 	struct afs_vnode *vnode = call->reply;
 	const __be32 *bp;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -696,16 +689,15 @@ int afs_fs_create(struct afs_server *server,
 /*
  * deliver reply data to an FS.RemoveFile or FS.RemoveDir
  */
-static int afs_deliver_fs_remove(struct afs_call *call,
-				 struct sk_buff *skb, bool last)
+static int afs_deliver_fs_remove(struct afs_call *call)
 {
 	struct afs_vnode *vnode = call->reply;
 	const __be32 *bp;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -777,16 +769,15 @@ int afs_fs_remove(struct afs_server *server,
 /*
  * deliver reply data to an FS.Link
  */
-static int afs_deliver_fs_link(struct afs_call *call,
-			       struct sk_buff *skb, bool last)
+static int afs_deliver_fs_link(struct afs_call *call)
 {
 	struct afs_vnode *dvnode = call->reply, *vnode = call->reply2;
 	const __be32 *bp;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -863,16 +854,15 @@ int afs_fs_link(struct afs_server *server,
 /*
  * deliver reply data to an FS.Symlink
  */
-static int afs_deliver_fs_symlink(struct afs_call *call,
-				  struct sk_buff *skb, bool last)
+static int afs_deliver_fs_symlink(struct afs_call *call)
 {
 	struct afs_vnode *vnode = call->reply;
 	const __be32 *bp;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -968,16 +958,15 @@ int afs_fs_symlink(struct afs_server *server,
 /*
  * deliver reply data to an FS.Rename
  */
-static int afs_deliver_fs_rename(struct afs_call *call,
-				  struct sk_buff *skb, bool last)
+static int afs_deliver_fs_rename(struct afs_call *call)
 {
 	struct afs_vnode *orig_dvnode = call->reply, *new_dvnode = call->reply2;
 	const __be32 *bp;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -1072,16 +1061,15 @@ int afs_fs_rename(struct afs_server *server,
 /*
  * deliver reply data to an FS.StoreData
  */
-static int afs_deliver_fs_store_data(struct afs_call *call,
-				     struct sk_buff *skb, bool last)
+static int afs_deliver_fs_store_data(struct afs_call *call)
 {
 	struct afs_vnode *vnode = call->reply;
 	const __be32 *bp;
 	int ret;
 
-	_enter(",,%u", last);
+	_enter("");
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -1251,17 +1239,16 @@ int afs_fs_store_data(struct afs_server *server, struct afs_writeback *wb,
 /*
  * deliver reply data to an FS.StoreStatus
  */
-static int afs_deliver_fs_store_status(struct afs_call *call,
-				       struct sk_buff *skb, bool last)
+static int afs_deliver_fs_store_status(struct afs_call *call)
 {
 	afs_dataversion_t *store_version;
 	struct afs_vnode *vnode = call->reply;
 	const __be32 *bp;
 	int ret;
 
-	_enter(",,%u", last);
+	_enter("");
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;
 
@@ -1443,14 +1430,13 @@ int afs_fs_setattr(struct afs_server *server, struct key *key,
 /*
  * deliver reply data to an FS.GetVolumeStatus
  */
-static int afs_deliver_fs_get_volume_status(struct afs_call *call,
-					    struct sk_buff *skb, bool last)
+static int afs_deliver_fs_get_volume_status(struct afs_call *call)
 {
 	const __be32 *bp;
 	char *p;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
 	switch (call->unmarshall) {
 	case 0:
@@ -1460,8 +1446,8 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 		/* extract the returned status record */
 	case 1:
 		_debug("extract status");
-		ret = afs_extract_data(call, skb, last, call->buffer,
-				       12 * 4);
+		ret = afs_extract_data(call, call->buffer,
+				       12 * 4, true);
 		if (ret < 0)
 			return ret;
 
@@ -1472,7 +1458,7 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 
 		/* extract the volume name length */
 	case 2:
-		ret = afs_extract_data(call, skb, last, &call->tmp, 4);
+		ret = afs_extract_data(call, &call->tmp, 4, true);
 		if (ret < 0)
 			return ret;
 
@@ -1487,8 +1473,8 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 	case 3:
 		_debug("extract volname");
 		if (call->count > 0) {
-			ret = afs_extract_data(call, skb, last, call->reply3,
-					       call->count);
+			ret = afs_extract_data(call, call->reply3,
+					       call->count, true);
 			if (ret < 0)
 				return ret;
 		}
@@ -1508,8 +1494,8 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 		call->count = 4 - (call->count & 3);
 
 	case 4:
-		ret = afs_extract_data(call, skb, last, call->buffer,
-				       call->count);
+		ret = afs_extract_data(call, call->buffer,
+				       call->count, true);
 		if (ret < 0)
 			return ret;
 
@@ -1519,7 +1505,7 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 
 		/* extract the offline message length */
 	case 5:
-		ret = afs_extract_data(call, skb, last, &call->tmp, 4);
+		ret = afs_extract_data(call, &call->tmp, 4, true);
 		if (ret < 0)
 			return ret;
 
@@ -1534,8 +1520,8 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 	case 6:
 		_debug("extract offline");
 		if (call->count > 0) {
-			ret = afs_extract_data(call, skb, last, call->reply3,
-					       call->count);
+			ret = afs_extract_data(call, call->reply3,
+					       call->count, true);
 			if (ret < 0)
 				return ret;
 		}
@@ -1555,8 +1541,8 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 		call->count = 4 - (call->count & 3);
 
 	case 7:
-		ret = afs_extract_data(call, skb, last, call->buffer,
-				       call->count);
+		ret = afs_extract_data(call, call->buffer,
+				       call->count, true);
 		if (ret < 0)
 			return ret;
 
@@ -1566,7 +1552,7 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 
 		/* extract the message of the day length */
 	case 8:
-		ret = afs_extract_data(call, skb, last, &call->tmp, 4);
+		ret = afs_extract_data(call, &call->tmp, 4, true);
 		if (ret < 0)
 			return ret;
 
@@ -1581,8 +1567,8 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 	case 9:
 		_debug("extract motd");
 		if (call->count > 0) {
-			ret = afs_extract_data(call, skb, last, call->reply3,
-					       call->count);
+			ret = afs_extract_data(call, call->reply3,
+					       call->count, true);
 			if (ret < 0)
 				return ret;
 		}
@@ -1595,26 +1581,17 @@ static int afs_deliver_fs_get_volume_status(struct afs_call *call,
 		call->unmarshall++;
 
 		/* extract the message of the day padding */
-		if ((call->count & 3) == 0) {
-			call->unmarshall++;
-			goto no_motd_padding;
-		}
-		call->count = 4 - (call->count & 3);
+		call->count = (4 - (call->count & 3)) & 3;
 
 	case 10:
-		ret = afs_extract_data(call, skb, last, call->buffer,
-				       call->count);
+		ret = afs_extract_data(call, call->buffer,
+				       call->count, false);
 		if (ret < 0)
 			return ret;
 
 		call->offset = 0;
 		call->unmarshall++;
-	no_motd_padding:
-
 	case 11:
-		ret = afs_data_complete(call, skb, last);
-		if (ret < 0)
-			return ret;
 		break;
 	}
 
@@ -1685,15 +1662,14 @@ int afs_fs_get_volume_status(struct afs_server *server,
 /*
  * deliver reply data to an FS.SetLock, FS.ExtendLock or FS.ReleaseLock
  */
-static int afs_deliver_fs_xxxx_lock(struct afs_call *call,
-				    struct sk_buff *skb, bool last)
+static int afs_deliver_fs_xxxx_lock(struct afs_call *call)
 {
 	const __be32 *bp;
 	int ret;
 
-	_enter("{%u},{%u},%d", call->unmarshall, skb->len, last);
+	_enter("{%u}", call->unmarshall);
 
-	ret = afs_transfer_reply(call, skb, last);
+	ret = afs_transfer_reply(call);
 	if (ret < 0)
 		return ret;