netdev - Re: [PATCH] net: sock: simplify tw proto registration

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Date:   Thu, 11 Mar 2021 10:40:09 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: sock: simplify tw proto registration

On Wed, Mar 10, 2021 at 10:42 AM Alexander Duyck
<alexander.duyck@...il.com> wrote:
>
> On Tue, Mar 9, 2021 at 5:48 PM Tonghao Zhang <xiangxia.m.yue@...il.com> wrote:
> >
> > On Wed, Mar 10, 2021 at 1:39 AM Alexander Duyck
> > <alexander.duyck@...il.com> wrote:
> > >
> > > On Mon, Mar 8, 2021 at 7:15 PM <xiangxia.m.yue@...il.com> wrote:
> > > >
> > > > From: Tonghao Zhang <xiangxia.m.yue@...il.com>
> > > >
> > > > Introduce a new function twsk_prot_init, inspired by
> > > > req_prot_init, to simplify the "proto_register" function.
> > > >
> > > > Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
> > > > ---
> > > >  net/core/sock.c | 44 ++++++++++++++++++++++++++++----------------
> > > >  1 file changed, 28 insertions(+), 16 deletions(-)
> > > >
> > > > diff --git a/net/core/sock.c b/net/core/sock.c
> > > > index 0ed98f20448a..610de4295101 100644
> > > > --- a/net/core/sock.c
> > > > +++ b/net/core/sock.c
> > > > @@ -3475,6 +3475,32 @@ static int req_prot_init(const struct proto *prot)
> > > >         return 0;
> > > >  }
> > > >
> > > > +static int twsk_prot_init(const struct proto *prot)
> > > > +{
> > > > +       struct timewait_sock_ops *twsk_prot = prot->twsk_prot;
> > > > +
> > > > +       if (!twsk_prot)
> > > > +               return 0;
> > > > +
> > > > +       twsk_prot->twsk_slab_name = kasprintf(GFP_KERNEL, "tw_sock_%s",
> > > > +                                             prot->name);
> > > > +       if (!twsk_prot->twsk_slab_name)
> > > > +               return -ENOMEM;
> > > > +
> > > > +       twsk_prot->twsk_slab =
> > > > +               kmem_cache_create(twsk_prot->twsk_slab_name,
> > > > +                                 twsk_prot->twsk_obj_size, 0,
> > > > +                                 SLAB_ACCOUNT | prot->slab_flags,
> > > > +                                 NULL);
> > > > +       if (!twsk_prot->twsk_slab) {
> > > > +               pr_crit("%s: Can't create timewait sock SLAB cache!\n",
> > > > +                       prot->name);
> > > > +               return -ENOMEM;
> > > > +       }
> > > > +
> > > > +       return 0;
> > > > +}
> > > > +
> > >
> > > So one issue here is that you have two returns but they both have the
> > > same error clean-up outside of the function. It might make more sense
> > > to look at freeing the kasprintf if the slab allocation fails and then
> > > using the out_free_request_sock_slab jump label below if the slab
> > > allocation failed.
> > Hi, thanks for your review.
> > if twsk_prot_init failed, (kasprintf, or slab alloc), we will invoke
> > the tw_prot_cleanup() to clean up
> > the sources allocated.
> > 1. kfree(twsk_prot->twsk_slab_name); // if name is NULL, kfree() will
> > return directly
> > 2. kmem_cache_destroy(twsk_prot->twsk_slab); // if slab is NULL,
> > kmem_cache_destroy() will return directly too.
> > so we don't care what err in twsk_prot_init().
> >
> > and req_prot_cleanup() will clean up all sources allocated for req_prot_init().
>
> I see. Okay so the expectation is that tw_prot_cleanup will take care
> of a partially initialized timewait_sock_ops.
>
> With that being the case the one change I would ask you to make would
> be to look at moving the function up so it is just below
> tw_prot_cleanup so it is obvious that the two are meant to be paired
> rather than placing it after req_prot_init.
Thanks, will be changed in v2
and change the new function name from twsk_prot_init to tw_prot_init
(tw_prot_cleanup).

> Otherwise the patch set itself looks good to me.
>
> Reviewed-by: Alexander Duyck <alexanderduyck@...com>



-- 
Best regards, Tonghao