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: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index e2673aa..e5202dd 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -262,16 +262,16 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
/* 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 @@
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 @@
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;
}