linux-kernel - RE: [[PATCH v1] 19/37] [CIFS] SMBD: Manage credits on SMBD client and server

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Date:   Mon, 14 Aug 2017 23:03:42 +0000
From:   Long Li <longli@...rosoft.com>
To:     Tom Talpey <ttalpey@...rosoft.com>,
        Steve French <sfrench@...ba.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "samba-technical@...ts.samba.org" <samba-technical@...ts.samba.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [[PATCH v1] 19/37] [CIFS] SMBD: Manage credits on SMBD client and
 server



> -----Original Message-----
> From: Tom Talpey
> Sent: Monday, August 14, 2017 1:47 PM
> To: Long Li <longli@...rosoft.com>; Steve French <sfrench@...ba.org>;
> linux-cifs@...r.kernel.org; samba-technical@...ts.samba.org; linux-
> kernel@...r.kernel.org
> Subject: RE: [[PATCH v1] 19/37] [CIFS] SMBD: Manage credits on SMBD client
> and server
> 
> > -----Original Message-----
> > From: linux-cifs-owner@...r.kernel.org [mailto:linux-cifs-
> > owner@...r.kernel.org] On Behalf Of Long Li
> > Sent: Wednesday, August 2, 2017 4:11 PM
> > To: Steve French <sfrench@...ba.org>; linux-cifs@...r.kernel.org;
> > samba- technical@...ts.samba.org; linux-kernel@...r.kernel.org
> > Cc: Long Li <longli@...rosoft.com>
> > Subject: [[PATCH v1] 19/37] [CIFS] SMBD: Manage credits on SMBD client
> > and server
> >
> >  /*
> > + * Extend the credits to remote peer
> > + * This implements [MS-SMBD] 3.1.5.9
> > + * The idea is that we should extend credits to remote peer as
> > +quickly as
> > + * it's allowed, to maintain data flow. We allocate as much as
> > +receive
> > + * buffer as possible, and extend the receive credits to remote peer
> > + * return value: the new credtis being granted.
> > + */
> > +static int manage_credits_prior_sending(struct cifs_rdma_info *info)
> > +{
> > +       int ret = 0;
> > +       struct cifs_rdma_response *response;
> > +       int rc;
> > +
> > +       if (atomic_read(&info->receive_credit_target) >
> 
> When does the receive_credit_target value change? It seems wasteful to
> perform an atomic_read() on this local value each time.

It could be potentially changed while receiving a SMBD packet, as specified in MS-SMBD 3.1.5.8.

I agree with you there is no need to use atomic since this value is not increased or decreased, just being set. Will change it.

> 
> Tom.