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

[Long Li]

> -----Original Message-----
> From: Tom Talpey
> Sent: Monday, August 14, 2017 1:47 PM
> To: Long Li <longli@xxxxxxxxxxxxx>; Steve French <sfrench@xxxxxxxxx>;
> linux-cifs@xxxxxxxxxxxxxxx; samba-technical@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: RE: [[PATCH v1] 19/37] [CIFS] SMBD: Manage credits on SMBD client
> and server
> 
> > -----Original Message-----
> > From: linux-cifs-owner@xxxxxxxxxxxxxxx [mailto:linux-cifs-
> > owner@xxxxxxxxxxxxxxx] On Behalf Of Long Li
> > Sent: Wednesday, August 2, 2017 4:11 PM
> > To: Steve French <sfrench@xxxxxxxxx>; linux-cifs@xxxxxxxxxxxxxxx;
> > samba- technical@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Cc: Long Li <longli@xxxxxxxxxxxxx>
> > 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.