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CIFS: Introduce credit-based flow control

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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>
This commit is contained in:
Pavel Shilovsky
2012-02-06 15:59:18 +04:00
committed by Steve French
parent fc40f9cf82
commit 2d86dbc970
6 changed files with 60 additions and 44 deletions
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14
fs/cifs/connect.c
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@@ -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;