CIFS: Introduce credit-based flow control
Pavel Shilovsky [Mon, 6 Feb 2012 11:59:18 +0000 (15:59 +0400)]
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: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifsglob.h
fs/cifs/cifsproto.h
fs/cifs/cifssmb.c
fs/cifs/connect.c
fs/cifs/misc.c
fs/cifs/transport.c

index fb78bc9..d55de96 100644 (file)
@@ -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;
 }
 
 /*
index 6f4e243..47a769e 100644 (file)
@@ -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 *);
index d7cbcfa..70aac35 100644 (file)
@@ -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 */
index ed91abc..1d48901 100644 (file)
@@ -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;
index 703ef5c..c273c12 100644 (file)
@@ -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);
+}
index e2673aa..e5202dd 100644 (file)
@@ -262,16 +262,16 @@ wait_for_free_request(struct TCP_Server_Info *server, const int long_op)
        if (long_op == CIFS_ASYNC_OP) {
                /* oplock breaks must not be held up */
                server->in_flight++;
+               server->credits--;
                spin_unlock(&server->req_lock);
                return 0;
        }
 
        while (1) {
-               if (server->in_flight >= server->maxReq) {
+               if (server->credits <= 0) {
                        spin_unlock(&server->req_lock);
                        cifs_num_waiters_inc(server);
-                       wait_event(server->request_q,
-                                  in_flight(server) < server->maxReq);
+                       wait_event(server->request_q, has_credits(server));
                        cifs_num_waiters_dec(server);
                        spin_lock(&server->req_lock);
                } else {
@@ -280,12 +280,16 @@ wait_for_free_request(struct TCP_Server_Info *server, const int long_op)
                                return -ENOENT;
                        }
 
-                       /* can not count locking commands against total
-                          as they are allowed to block on server */
+                       /*
+                        * Can not count locking commands against total
+                        * as they are allowed to block on server.
+                        */
 
                        /* update # of requests on the wire to server */
-                       if (long_op != CIFS_BLOCKING_OP)
+                       if (long_op != CIFS_BLOCKING_OP) {
+                               server->credits--;
                                server->in_flight++;
+                       }
                        spin_unlock(&server->req_lock);
                        break;
                }
@@ -360,7 +364,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
        mid = AllocMidQEntry(hdr, server);
        if (mid == NULL) {
                mutex_unlock(&server->srv_mutex);
-               dec_in_flight(server);
+               cifs_add_credits(server, 1);
                wake_up(&server->request_q);
                return -ENOMEM;
        }
@@ -393,7 +397,7 @@ cifs_call_async(struct TCP_Server_Info *server, struct kvec *iov,
        return rc;
 out_err:
        delete_mid(mid);
-       dec_in_flight(server);
+       cifs_add_credits(server, 1);
        wake_up(&server->request_q);
        return rc;
 }
@@ -565,8 +569,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
                mutex_unlock(&ses->server->srv_mutex);
                cifs_small_buf_release(in_buf);
                /* Update # of requests on wire to server */
-               dec_in_flight(ses->server);
-               wake_up(&ses->server->request_q);
+               cifs_add_credits(ses->server, 1);
                return rc;
        }
        rc = cifs_sign_smb2(iov, n_vec, ses->server, &midQ->sequence_number);
@@ -602,8 +605,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
                        midQ->callback = DeleteMidQEntry;
                        spin_unlock(&GlobalMid_Lock);
                        cifs_small_buf_release(in_buf);
-                       dec_in_flight(ses->server);
-                       wake_up(&ses->server->request_q);
+                       cifs_add_credits(ses->server, 1);
                        return rc;
                }
                spin_unlock(&GlobalMid_Lock);
@@ -613,8 +615,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
 
        rc = cifs_sync_mid_result(midQ, ses->server);
        if (rc != 0) {
-               dec_in_flight(ses->server);
-               wake_up(&ses->server->request_q);
+               cifs_add_credits(ses->server, 1);
                return rc;
        }
 
@@ -638,8 +639,7 @@ SendReceive2(const unsigned int xid, struct cifs_ses *ses,
                midQ->resp_buf = NULL;
 out:
        delete_mid(midQ);
-       dec_in_flight(ses->server);
-       wake_up(&ses->server->request_q);
+       cifs_add_credits(ses->server, 1);
 
        return rc;
 }
@@ -689,8 +689,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
        if (rc) {
                mutex_unlock(&ses->server->srv_mutex);
                /* Update # of requests on wire to server */
-               dec_in_flight(ses->server);
-               wake_up(&ses->server->request_q);
+               cifs_add_credits(ses->server, 1);
                return rc;
        }
 
@@ -722,8 +721,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
                        /* no longer considered to be "in-flight" */
                        midQ->callback = DeleteMidQEntry;
                        spin_unlock(&GlobalMid_Lock);
-                       dec_in_flight(ses->server);
-                       wake_up(&ses->server->request_q);
+                       cifs_add_credits(ses->server, 1);
                        return rc;
                }
                spin_unlock(&GlobalMid_Lock);
@@ -731,8 +729,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
 
        rc = cifs_sync_mid_result(midQ, ses->server);
        if (rc != 0) {
-               dec_in_flight(ses->server);
-               wake_up(&ses->server->request_q);
+               cifs_add_credits(ses->server, 1);
                return rc;
        }
 
@@ -748,8 +745,7 @@ SendReceive(const unsigned int xid, struct cifs_ses *ses,
        rc = cifs_check_receive(midQ, ses->server, 0);
 out:
        delete_mid(midQ);
-       dec_in_flight(ses->server);
-       wake_up(&ses->server->request_q);
+       cifs_add_credits(ses->server, 1);
 
        return rc;
 }