Ocfs2 devel - May 2020 - [PATCH 31/33] sctp: add sctp_sock_set_nodelay

On Wed, May 20, 2020 at 08:39:13PM -0300, Marcelo Ricardo Leitner
wrote:
> On Wed, May 20, 2020 at 04:23:55PM -0700, David Miller wrote:
> > From: Marcelo Ricardo Leitner <marcelo.leitner at gmail.com>
> > Date: Wed, 20 May 2020 20:10:01 -0300
> > 
> > > The duplication with sctp_setsockopt_nodelay() is quite
silly/bad.
> > > Also, why have the 'true' hardcoded? It's what dlm
uses, yes, but the
> > > API could be a bit more complete than that.
> > 
> > The APIs are being designed based upon what in-tree users actually
> > make use of.  We can expand things later if necessary.
> 
> Sometimes expanding things later can be though, thus why the worry.
> But ok, I get it. Thanks.
> 
> The comment still applies, though. (re the duplication)
Where do you see duplication?

sctp_setsockopt_nodelay does the following things:

 - verifies optlen, returns -EINVAL if it doesn't match
 - calls get_user, returns -EFAULT on error
 - converts the value from get_user to a boolean and assigns it
   to sctp_sk(sk)->nodelay
 - returns 0.

sctp_sock_set_nodelay does:

 - call lock_sock
 - assign true to sctp_sk(sk)->nodelay
 - call release_sock
 - does not return an error code

From: Christoph Hellwig
> Sent: 21 May 2020 09:35
> On Wed, May 20, 2020 at 08:39:13PM -0300, Marcelo Ricardo Leitner wrote:
> > On Wed, May 20, 2020 at 04:23:55PM -0700, David Miller wrote:
> > > From: Marcelo Ricardo Leitner <marcelo.leitner at
gmail.com>
> > > Date: Wed, 20 May 2020 20:10:01 -0300
> > >
> > > > The duplication with sctp_setsockopt_nodelay() is quite
silly/bad.
> > > > Also, why have the 'true' hardcoded? It's what
dlm uses, yes, but the
> > > > API could be a bit more complete than that.
> > >
> > > The APIs are being designed based upon what in-tree users
actually
> > > make use of.  We can expand things later if necessary.
> >
> > Sometimes expanding things later can be though, thus why the worry.
> > But ok, I get it. Thanks.
> >
> > The comment still applies, though. (re the duplication)
> 
> Where do you see duplication?
The whole thing just doesn't scale.

As soon as you get to the slightly more complex requests
like SCTP_INITMSG (which should probably be called to
set the required number of data streams) you've either
got replicated code or nested wrappers.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT,
UK
Registration No: 1397386 (Wales)

On Thu, May 21, 2020 at 10:34:42AM +0200, Christoph Hellwig
wrote:
> On Wed, May 20, 2020 at 08:39:13PM -0300, Marcelo Ricardo Leitner wrote:
> > On Wed, May 20, 2020 at 04:23:55PM -0700, David Miller wrote:
> > > From: Marcelo Ricardo Leitner <marcelo.leitner at
gmail.com>
> > > Date: Wed, 20 May 2020 20:10:01 -0300
> > > 
> > > > The duplication with sctp_setsockopt_nodelay() is quite
silly/bad.
> > > > Also, why have the 'true' hardcoded? It's what
dlm uses, yes, but the
> > > > API could be a bit more complete than that.
> > > 
> > > The APIs are being designed based upon what in-tree users
actually
> > > make use of.  We can expand things later if necessary.
> > 
> > Sometimes expanding things later can be though, thus why the worry.
> > But ok, I get it. Thanks.
> > 
> > The comment still applies, though. (re the duplication)
> 
> Where do you see duplication?
> 
> sctp_setsockopt_nodelay does the following things:
> 
>  - verifies optlen, returns -EINVAL if it doesn't match
>  - calls get_user, returns -EFAULT on error
>  - converts the value from get_user to a boolean and assigns it
>    to sctp_sk(sk)->nodelay
>  - returns 0.
> 
> sctp_sock_set_nodelay does:
> 
>  - call lock_sock
>  - assign true to sctp_sk(sk)->nodelay
>  - call release_sock
>  - does not return an error code
With the patch there are now two ways of enabling nodelay. It may be
just a boolean set today, but if one wants to probe on it or if we
want to extend it with anything, say a debug msg, we have to do it in
two (very different) places.