[RFC PATCH 23/36] cifs: Clean up mid->callback_data and kill off mid->creator

[David Howells <dhowells@redhat.com>]

We shouldn't really be pinning a task_struct on the mid_q_struct.  Better
to provide a wait queue there and have the waiter wait on it.  For
synchronous operations, this allows them to remove themselves from it once
this is absorbed into smb_message and smb_message is generated higher up
the stack.  This also gets rid of one of the uses of mid->callback_data.

We can also get rid of the need for callback_data for the Echo command
callback by passing a server pointer down into ->callback() from the
callers (all of which have it available).  This can also be used in the
Read and Write callbacks.

We then only need the callback_data for the Read and Write commands - and
in both cases, it points to a cifs_io_subrequest struct.  So replace
callback_data with a specifically typed pointer in a union that other users
can be added to as the need arises.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: Tom Talpey <tom@talpey.com>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
 fs/smb/client/cifs_debug.c    |  3 +--
 fs/smb/client/cifsglob.h      | 11 ++++++++---
 fs/smb/client/cifssmb.c       |  7 ++-----
 fs/smb/client/smb1debug.c     |  7 ++++---
 fs/smb/client/smb2ops.c       |  5 +++--
 fs/smb/client/smb2pdu.c       |  9 ++++-----
 fs/smb/client/smb2transport.c |  6 ------
 fs/smb/client/transport.c     |  7 +++----
 8 files changed, 25 insertions(+), 30 deletions(-)

diff --git a/fs/smb/client/cifs_debug.c b/fs/smb/client/cifs_debug.c
index 47dadab67440..0e3e790bbdbc 100644
--- a/fs/smb/client/cifs_debug.c
+++ b/fs/smb/client/cifs_debug.c
@@ -659,11 +659,10 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 					   chan_server->conn_id);
 				spin_lock(&chan_server->mid_queue_lock);
 				list_for_each_entry(smb, &chan_server->pending_mid_q, qhead) {
-					seq_printf(m, "\n\t\tState: %d com: %d pid: %d cbdata: %p mid %llu",
+					seq_printf(m, "\n\t\tState: %d com: %d pid: %d mid %llu",
 						   smb->mid_state,
 						   le16_to_cpu(smb->command),
 						   smb->pid,
-						   smb->callback_data,
 						   smb->mid);
 				}
 				spin_unlock(&chan_server->mid_queue_lock);
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 6b90f17ae0fa..3a2f684cede9 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1636,7 +1636,8 @@ static inline void cifs_stats_bytes_read(struct cifs_tcon *tcon,
  * - it will be called by cifsd, with no locks held
  * - the mid will be removed from any lists
  */
-typedef void (*mid_callback_t)(struct TCP_Server_Info *srv, struct smb_message *smb);
+typedef void (*mid_callback_t)(struct TCP_Server_Info *server,
+			       struct smb_message *smb);
 
 /*
  * Definition of an SMB request message to be transmitted.  These may be
@@ -1668,12 +1669,18 @@ struct smb_message {
 	struct smb_message	*next;		/* Next message in compound */
 	struct cifs_credits	credits;	/* Credit requirements for this message */
 	void			*request;	/* Pointer to request message body */
+	wait_queue_head_t	waitq;		/* Wait queue for message events */
 	refcount_t		ref;
 	unsigned int		debug_id;	/* Debugging ID for tracing */
 	bool			sensitive;	/* Request contains sensitive data */
 	bool			cancelled;	/* T if cancelled */
 	unsigned int		sr_flags;	/* Flags passed to send_recv() */
 
+	/* PDU-type specific data */
+	union {
+		struct cifs_io_subrequest *subreq; /* Read/write subrequest */
+	};
+
 	/* Queue state */
 	struct list_head	qhead;		/* mids waiting on reply from this server */
 	__u64			mid;		/* multiplex id */
@@ -1687,8 +1694,6 @@ struct smb_message {
 	unsigned long		when_received;	/* when demux complete (taken off wire) */
 #endif
 	mid_callback_t		callback;	/* call completion callback */
-	void			*callback_data;	/* general purpose pointer for callback */
-	struct task_struct	*creator;
 	int			mid_state;	/* wish this were enum but can not pass to wait_event */
 	int			mid_rc;		/* rc for MID_RC */
 	unsigned int		optype;		/* operation type */
diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index ca6410e1f39e..e36828359f67 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -737,7 +737,6 @@ CIFSSMBEcho(struct TCP_Server_Info *server)
 	smb->request		= req;
 	smb->total_len		= in_len;
 	smb->callback		= cifs_echo_callback;
-	smb->callback_data	= server;
 
 	rc = cifs_call_async(server, smb, CIFS_NON_BLOCKING | CIFS_ECHO_OP, NULL);
 	if (rc)
@@ -1428,7 +1427,7 @@ CIFS_open(const unsigned int xid, struct cifs_open_parms *oparms, int *oplock,
 static void
 cifs_readv_callback(struct TCP_Server_Info *server, struct smb_message *smb)
 {
-	struct cifs_io_subrequest *rdata = smb->callback_data;
+	struct cifs_io_subrequest *rdata = smb->subreq;
 	struct netfs_inode *ictx = netfs_inode(rdata->rreq->inode);
 	struct cifs_tcon *tcon = tlink_tcon(rdata->req->cfile->tlink);
 	struct inode *inode = &ictx->inode;
@@ -1595,7 +1594,6 @@ cifs_async_readv(struct cifs_io_subrequest *rdata)
 	smb->request		= req;
 	smb->total_len		= in_len;
 	smb->callback		= cifs_readv_callback;
-	smb->callback_data	= rdata;
 	smb->copy_to_bufs	= true;
 
 	iov_iter_bvec_queue(&smb->response_iter, ITER_DEST,
@@ -1860,7 +1858,7 @@ CIFSSMBWrite(const unsigned int xid, struct cifs_io_parms *io_parms,
 static void
 cifs_writev_callback(struct TCP_Server_Info *server, struct smb_message *smb)
 {
-	struct cifs_io_subrequest *wdata = smb->callback_data;
+	struct cifs_io_subrequest *wdata = smb->subreq;
 	struct cifs_tcon *tcon = tlink_tcon(wdata->req->cfile->tlink);
 	WRITE_RSP *rsp = (WRITE_RSP *)smb->response;
 	struct cifs_credits credits = {
@@ -1975,7 +1973,6 @@ cifs_async_writev(struct cifs_io_subrequest *wdata)
 	smb->total_len		= in_len + 1;
 	smb->total_len		+= wdata->subreq.len;
 	smb->callback		= cifs_writev_callback;
-	smb->callback_data	= wdata;
 
 	iov_iter_bvec_queue(&smb->rqst.rq_iter, ITER_DEST,
 			    wdata->subreq.content.bvecq, wdata->subreq.content.slot,
diff --git a/fs/smb/client/smb1debug.c b/fs/smb/client/smb1debug.c
index 048fe6303bc1..6eb87852bce7 100644
--- a/fs/smb/client/smb1debug.c
+++ b/fs/smb/client/smb1debug.c
@@ -40,11 +40,12 @@ void cifs_dump_mids(struct TCP_Server_Info *server)
 			.data_offset	= smb->resp_data_offset,
 		};
 
-		cifs_dbg(VFS, "State: %d Cmd: %d Pid: %d Cbdata: %p Mid %llu\n",
+		cifs_dbg(VFS, "State: %d Cmd: %x Pid: %d R=%x[%x] Mid %llu\n",
 			 smb->mid_state,
-			 le16_to_cpu(smb->command),
+			 le32_to_cpu(smb->command),
 			 smb->pid,
-			 smb->callback_data,
+			 smb->subreq ? smb->subreq->rreq->debug_id : 0,
+			 smb->subreq ? smb->subreq->subreq.debug_index : 0,
 			 smb->mid);
 #ifdef CONFIG_CIFS_STATS2
 		cifs_dbg(VFS, "IsLarge: %d buf: %p time rcv: %ld now: %ld\n",
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 0aaefe901fbd..b655c0f626f5 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -485,11 +485,12 @@ void smb2_dump_mids(struct TCP_Server_Info *server)
 			.data_offset	= smb->resp_data_offset,
 		};
 
-		cifs_dbg(VFS, "State: %d Cmd: %d Pid: %d Cbdata: %p Mid %llu\n",
+		cifs_dbg(VFS, "State: %d Cmd: %d Pid: %d R=%x[%x] Mid %llu\n",
 			 smb->mid_state,
 			 smb->command,
 			 smb->pid,
-			 smb->callback_data,
+			 smb->subreq ? smb->subreq->rreq->debug_id : 0,
+			 smb->subreq ? smb->subreq->subreq.debug_index : 0,
 			 smb->mid);
 #ifdef CONFIG_CIFS_STATS2
 		cifs_dbg(VFS, "IsLarge: %d buf: %p time rcv: %ld now: %ld\n",
diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index 2a234df2fad5..f4ea7256b09d 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -4386,7 +4386,6 @@ SMB2_echo(struct TCP_Server_Info *server)
 	smb->request		= req;
 	smb->total_len		= total_len;
 	smb->callback		= smb2_echo_callback;
-	smb->callback_data	= server;
 
 	req->hdr.CreditRequest = cpu_to_le16(1);
 
@@ -4629,7 +4628,7 @@ smb2_new_read_req(void **buf, unsigned int *total_len,
 static void
 smb2_readv_callback(struct TCP_Server_Info *server, struct smb_message *smb)
 {
-	struct cifs_io_subrequest *rdata = smb->callback_data;
+	struct cifs_io_subrequest *rdata = smb->subreq;
 	struct netfs_inode *ictx = netfs_inode(rdata->rreq->inode);
 	struct cifs_tcon *tcon = tlink_tcon(rdata->req->cfile->tlink);
 	struct smb2_hdr *shdr = smb->response;
@@ -4828,7 +4827,7 @@ smb2_async_readv(struct cifs_io_subrequest *rdata)
 	smb->request		= buf;
 	smb->total_len		= total_len;
 	smb->callback		= smb2_readv_callback;
-	smb->callback_data	= rdata;
+	smb->subreq		= rdata;
 	smb->copy_to_bufs	= true;
 
 	iov_iter_bvec_queue(&smb->response_iter, ITER_DEST,
@@ -4981,7 +4980,7 @@ SMB2_read(const unsigned int xid, struct cifs_io_parms *io_parms,
 static void
 smb2_writev_callback(struct TCP_Server_Info *server, struct smb_message *smb)
 {
-	struct cifs_io_subrequest *wdata = smb->callback_data;
+	struct cifs_io_subrequest *wdata = smb->subreq;
 	struct cifs_tcon *tcon = tlink_tcon(wdata->req->cfile->tlink);
 	struct smb2_write_rsp *rsp = (struct smb2_write_rsp *)smb->response;
 	struct cifs_credits credits = {
@@ -5160,7 +5159,7 @@ smb2_async_writev(struct cifs_io_subrequest *wdata)
 	smb->request		= req;
 	smb->total_len		= total_len;
 	smb->callback		= smb2_writev_callback;
-	smb->callback_data	= wdata;
+	smb->subreq		= wdata;
 
 	iov_iter_bvec_queue(&smb->rqst.rq_iter, ITER_SOURCE,
 			    wdata->subreq.content.bvecq, wdata->subreq.content.slot,
diff --git a/fs/smb/client/smb2transport.c b/fs/smb/client/smb2transport.c
index 73db90ab8a52..14ee09b33f2c 100644
--- a/fs/smb/client/smb2transport.c
+++ b/fs/smb/client/smb2transport.c
@@ -611,12 +611,6 @@ static void smb2_init_mid(struct smb_message *smb,
 
 	smb->credits_consumed = credits > 0 ? credits : 1;
 
-	/*
-	 * The default is for the mid to be synchronous, so the
-	 * default callback just wakes up the current task.
-	 */
-	smb->creator = get_task_struct(current);
-
 	atomic_inc(&mid_count);
 	trace_smb3_cmd_enter(le32_to_cpu(shdr->Id.SyncId.TreeId),
 			     le64_to_cpu(shdr->SessionId),
diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index 0a7b2e7922cf..68536de2c1a0 100644
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -53,8 +53,8 @@ struct smb_message *smb_message_alloc(enum smb_command_trace cmd, gfp_t gfp)
 		 * callback just wakes up the current task.
 		 */
 		smb->callback		= cifs_wake_up_task;
-		smb->callback_data	= current;
 		smb->mid_state		= MID_REQUEST_ALLOCATED;
+		init_waitqueue_head(&smb->waitq);
 		trace_smb3_message(smb->debug_id, 1, (enum smb_message_trace)cmd);
 	}
 	return smb;
@@ -122,7 +122,7 @@ cifs_wake_up_task(struct TCP_Server_Info *server, struct smb_message *smb)
 	if (smb->mid_state == MID_RESPONSE_RECEIVED)
 		smb->mid_state = MID_RESPONSE_READY;
 	smb_see_message(smb, smb_message_trace_see_wake_up_task);
-	wake_up_process(smb->callback_data);
+	wake_up_all(&smb->waitq);
 }
 
 static void smb_clear_mid(struct TCP_Server_Info *server, struct smb_message *smb)
@@ -199,7 +199,6 @@ static void smb_clear_mid(struct TCP_Server_Info *server, struct smb_message *sm
 		}
 	}
 #endif
-	put_task_struct(smb->creator);
 }
 
 static bool discard_message(struct TCP_Server_Info *server, struct smb_message *smb)
@@ -901,7 +900,7 @@ int wait_for_response(struct TCP_Server_Info *server, struct smb_message *smb)
 	if (smb->sr_flags & CIFS_INTERRUPTIBLE_WAIT)
 		sleep_state = TASK_INTERRUPTIBLE;
 
-	error = wait_event_state(server->response_q,
+	error = wait_event_state(smb->waitq,
 				 smb->mid_state != MID_REQUEST_SUBMITTED &&
 				 smb->mid_state != MID_RESPONSE_RECEIVED,
 				 (sleep_state | TASK_FREEZABLE_UNSAFE));