linux-kernel - Re: [PATCH 25/44] kdbus: Cleanup kdbus_cmd_conn

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Date:	Fri, 9 Oct 2015 21:45:27 +0300
From:	Sergei Zviagintsev <sergei@...v.net>
To:	David Herrmann <dh.herrmann@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 25/44] kdbus: Cleanup kdbus_cmd_conn_info()

Hi,

On Thu, Oct 08, 2015 at 04:38:11PM +0200, David Herrmann wrote:
> Hi
> 
> On Thu, Oct 8, 2015 at 1:31 PM, Sergei Zviagintsev <sergei@...v.net> wrote:
> >  - Move `entry' and `owner' to the scope where they are used. Drop
> >    redundand initialization of `entry'. Use conditional operator to set
> >    the value of `owner'.
> >
> >  - Set `ret' to zero right after call to kdbus_pool_slice_copy_kvec(),
> >    not in the end of function.
> >
> >  - Remove redundant goto.
> >
> > Signed-off-by: Sergei Zviagintsev <sergei@...v.net>
> > ---
> >  ipc/kdbus/connection.c | 16 +++++++---------
> >  1 file changed, 7 insertions(+), 9 deletions(-)
> >
> > diff --git a/ipc/kdbus/connection.c b/ipc/kdbus/connection.c
> > index b3c5f20a57d8..6a73ac3f444d 100644
> > --- a/ipc/kdbus/connection.c
> > +++ b/ipc/kdbus/connection.c
> > @@ -1702,8 +1702,6 @@ int kdbus_cmd_conn_info(struct kdbus_conn *conn, void __user *argp)
> >  {
> >         struct kdbus_meta_conn *conn_meta = NULL;
> >         struct kdbus_pool_slice *slice = NULL;
> > -       struct kdbus_name_entry *entry = NULL;
> > -       struct kdbus_name_owner *owner = NULL;
> >         struct kdbus_conn *owner_conn = NULL;
> >         struct kdbus_item *meta_items = NULL;
> >         struct kdbus_info info = {};
> > @@ -1739,9 +1737,12 @@ int kdbus_cmd_conn_info(struct kdbus_conn *conn, void __user *argp)
> >         name = argv[1].item ? argv[1].item->str : NULL;
> >
> >         if (name) {
> > +               struct kdbus_name_entry *entry;
> > +               struct kdbus_name_owner *owner;
> > +
> >                 entry = kdbus_name_lookup_unlocked(bus->name_registry, name);
> > -               if (entry)
> > -                       owner = kdbus_name_get_owner(entry);
> > +               owner = entry ? kdbus_name_get_owner(entry) : NULL;
> > +
> 
> This looks good to me.
> 
> >                 if (!owner ||
> >                     !kdbus_conn_policy_see_name(conn, current_cred(), name) ||
> >                     (cmd->id != 0 && owner->conn->id != cmd->id)) {
> > @@ -1804,17 +1805,14 @@ int kdbus_cmd_conn_info(struct kdbus_conn *conn, void __user *argp)
> >         ret = kdbus_pool_slice_copy_kvec(slice, 0, kvec, cnt, size);
> >         if (ret < 0)
> >                 goto exit;
> > +       ret = 0;
> >
> >         kdbus_pool_slice_publish(slice, &cmd->offset, &cmd->info_size);
> >
> >         if (kdbus_member_set_user(&cmd->offset, argp, typeof(*cmd), offset) ||
> >             kdbus_member_set_user(&cmd->info_size, argp,
> > -                                 typeof(*cmd), info_size)) {
> > +                                 typeof(*cmd), info_size))
> >                 ret = -EFAULT;
> > -               goto exit;
> > -       }
> > -
> > -       ret = 0;
> 
> Again, why? Now you have a random "ret = 0;" somewhere in between,
> instead of directly at the tail of the success-path.

This change was intended to stress to one who is reading the code that
kdbus_pool_slice_copy_kvec() returns >= 0 on success (as it returns the
number of bytes copied in contrast to most of functions which return 0 on
success). The only reason we have 'ret = 0' in the end of the function
is to reset `ret' after kdbus_pool_slice_copy_kvec(), so I decided to
group it together. Without kdbus_pool_slice_copy_kvec() we could return
`ret' as is, because it is always zero on success path.

BTW, kdbus_node_link() for example does the same: uses `ret' to handle
the return val of ida_simple_get() and then reset it to zero
immediately.

But that's too much words on such a simple change. I don't mind omitting
it from v2.

> 
> Thanks
> David
> 
> >
> >  exit:
> >         up_read(&bus->name_registry->rwlock);
> > --
> > 1.8.3.1
> >
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