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Commit 2d86dbc9 authored by Pavel Shilovsky's avatar Pavel Shilovsky Committed by Steve French
Browse files

CIFS: Introduce credit-based flow control 



and send no more than credits value requests at once. For SMB/CIFS
it's trivial: increment this value by receiving any message and
decrement by sending one.

Reviewed-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarPavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: default avatarSteve French <sfrench@us.ibm.com>
parent fc40f9cf

fs/cifs/cifsglob.h

+7 −4
Original line number Diff line number Diff line
@@ -250,8 +250,9 @@ struct TCP_Server_Info { 
	bool noblocksnd;		/* use blocking sendmsg */

	bool noautotune;		/* do not autotune send buf sizes */

	bool tcp_nodelay;

	int credits;  /* send no more requests at once */

	unsigned int in_flight;  /* number of requests on the wire to server */

	spinlock_t req_lock; /* protect the value above */

	spinlock_t req_lock;  /* protect the two values above */

	struct mutex srv_mutex;

	struct task_struct *tsk;

	char server_GUID[16];
@@ -314,12 +315,14 @@ in_flight(struct TCP_Server_Info *server) 
	return num;

}



static inline void

dec_in_flight(struct TCP_Server_Info *server)

static inline bool

has_credits(struct TCP_Server_Info *server)

{

	int num;

	spin_lock(&server->req_lock);

	server->in_flight--;

	num = server->credits;

	spin_unlock(&server->req_lock);

	return num > 0;

}



/*

fs/cifs/cifsproto.h

+3 −0
Original line number Diff line number Diff line
@@ -88,6 +88,9 @@ extern int SendReceiveBlockingLock(const unsigned int xid, 
			struct smb_hdr *in_buf ,

			struct smb_hdr *out_buf,

			int *bytes_returned);

extern void cifs_add_credits(struct TCP_Server_Info *server,

			     const unsigned int add);

extern void cifs_set_credits(struct TCP_Server_Info *server, const int val);

extern int checkSMB(struct smb_hdr *smb, __u16 mid, unsigned int length);

extern bool is_valid_oplock_break(struct smb_hdr *smb,

				  struct TCP_Server_Info *);

fs/cifs/cifssmb.c

+5 −8
Original line number Diff line number Diff line
@@ -461,7 +461,7 @@ CIFSSMBNegotiate(unsigned int xid, struct cifs_ses *ses) 
		server->maxReq = min_t(unsigned int,

				       le16_to_cpu(rsp->MaxMpxCount),

				       cifs_max_pending);

		server->oplocks = server->maxReq > 1 ? enable_oplocks : false;

		cifs_set_credits(server, server->maxReq);

		server->maxBuf = le16_to_cpu(rsp->MaxBufSize);

		server->max_vcs = le16_to_cpu(rsp->MaxNumberVcs);

		/* even though we do not use raw we might as well set this
@@ -569,7 +569,7 @@ CIFSSMBNegotiate(unsigned int xid, struct cifs_ses *ses) 
	   little endian */

	server->maxReq = min_t(unsigned int, le16_to_cpu(pSMBr->MaxMpxCount),

			       cifs_max_pending);

	server->oplocks = server->maxReq > 1 ? enable_oplocks : false;

	cifs_set_credits(server, server->maxReq);

	/* probably no need to store and check maxvcs */

	server->maxBuf = le32_to_cpu(pSMBr->MaxBufferSize);

	server->max_rw = le32_to_cpu(pSMBr->MaxRawSize);
@@ -721,8 +721,7 @@ cifs_echo_callback(struct mid_q_entry *mid) 
	struct TCP_Server_Info *server = mid->callback_data;



	DeleteMidQEntry(mid);

	dec_in_flight(server);

	wake_up(&server->request_q);

	cifs_add_credits(server, 1);

}



int
@@ -1674,8 +1673,7 @@ cifs_readv_callback(struct mid_q_entry *mid) 


	queue_work(system_nrt_wq, &rdata->work);

	DeleteMidQEntry(mid);

	dec_in_flight(server);

	wake_up(&server->request_q);

	cifs_add_credits(server, 1);

}



/* cifs_async_readv - send an async write, and set up mid to handle result */
@@ -2115,8 +2113,7 @@ cifs_writev_callback(struct mid_q_entry *mid) 


	queue_work(system_nrt_wq, &wdata->work);

	DeleteMidQEntry(mid);

	dec_in_flight(tcon->ses->server);

	wake_up(&tcon->ses->server->request_q);

	cifs_add_credits(tcon->ses->server, 1);

}



/* cifs_async_writev - send an async write, and set up mid to handle result */

fs/cifs/connect.c

+6 −8
Original line number Diff line number Diff line
@@ -642,14 +642,10 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server) 
	spin_unlock(&GlobalMid_Lock);

	wake_up_all(&server->response_q);



	/* Check if we have blocked requests that need to free. */

	/* check if we have blocked requests that need to free */

	spin_lock(&server->req_lock);

	if (server->in_flight >= server->maxReq)

		server->in_flight = server->maxReq - 1;

	/*

	 * We do not want to set the max_pending too low or we could end up

	 * with the counter going negative.

	 */

	if (server->credits <= 0)

		server->credits = 1;

	spin_unlock(&server->req_lock);

	/*

	 * Although there should not be any requests blocked on this queue it
@@ -1906,7 +1902,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info) 
	tcp_ses->noautotune = volume_info->noautotune;

	tcp_ses->tcp_nodelay = volume_info->sockopt_tcp_nodelay;

	tcp_ses->in_flight = 0;

	tcp_ses->maxReq = 1; /* enough to send negotiate request */

	tcp_ses->credits = 1;

	init_waitqueue_head(&tcp_ses->response_q);

	init_waitqueue_head(&tcp_ses->request_q);

	INIT_LIST_HEAD(&tcp_ses->pending_mid_q);
@@ -3757,9 +3753,11 @@ int cifs_negotiate_protocol(unsigned int xid, struct cifs_ses *ses) 
	if (server->maxBuf != 0)

		return 0;



	cifs_set_credits(server, 1);

	rc = CIFSSMBNegotiate(xid, ses);

	if (rc == -EAGAIN) {

		/* retry only once on 1st time connection */

		cifs_set_credits(server, 1);

		rc = CIFSSMBNegotiate(xid, ses);

		if (rc == -EAGAIN)

			rc = -EHOSTDOWN;

fs/cifs/misc.c

+19 −0
Original line number Diff line number Diff line
@@ -690,3 +690,22 @@ backup_cred(struct cifs_sb_info *cifs_sb) 


	return false;

}



void

cifs_add_credits(struct TCP_Server_Info *server, const unsigned int add)

{

	spin_lock(&server->req_lock);

	server->credits += add;

	server->in_flight--;

	spin_unlock(&server->req_lock);

	wake_up(&server->request_q);

}



void

cifs_set_credits(struct TCP_Server_Info *server, const int val)

{

	spin_lock(&server->req_lock);

	server->credits = val;

	server->oplocks = val > 1 ? enable_oplocks : false;

	spin_unlock(&server->req_lock);

}