linux-kernel - Re: [PATCH 9/9] fs: dlm: lockd: Convert int result to unsigned char type

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Message-ID: <1406174039.2755.71.camel@joe-AO725>
Date:	Wed, 23 Jul 2014 20:53:59 -0700
From:	Joe Perches <joe@...ches.com>
To:	Jeff Layton <jlayton@...chiereds.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	David Teigland <teigland@...hat.com>,
	Christine Caulfield <ccaulfie@...hat.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	cluster-devel@...hat.com, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 9/9] fs: dlm: lockd: Convert int result to unsigned char
 type

On Wed, 2014-07-23 at 14:11 -0400, Jeff Layton wrote:
> On Sun, 20 Jul 2014 11:23:43 -0700 Joe Perches <joe@...ches.com> wrote:
> > op->info.rv is an s32, but it's only used as a u8.
> I don't understand this patch. info.rv is s32 (and I assume that "rv"
> stands for "return value").

In this case it's not a return value but an input.

> What I don't get is why you think it's just
> used as a u8.

Because it's tested only in nlmsvc_grant_deferred
and nlmsvc_update_deferred_block against 0.

As far as I can tell, it's not possible to set it
to a negative value.

> It seems to be used more like a bool than anything else,
> and I'm not sure that "type" is really a good description for it. Maybe
> it should be a "bool" and named "conflict",

Maybe.  But it seemed likely and possible to expand
it from a single bool to a value.

> given the comments in dlm_posix_get ?

Maybe, though I don't see how the comments relate to
this change.  The rv value returned from that call
is either -ENOMEM or 0 and is unchanged by this patch.

> > diff --git a/include/linux/fs.h b/include/linux/fs.h
[]
> > @@ -842,7 +842,7 @@ struct lock_manager_operations {
> >  	int (*lm_compare_owner)(struct file_lock *fl1, struct file_lock *fl2);
> >  	unsigned long (*lm_owner_key)(struct file_lock *fl);
> >  	void (*lm_notify)(struct file_lock *fl);	/* unblock callback */
> > -	int (*lm_grant)(struct file_lock *fl, int result);
> > +	int (*lm_grant)(struct file_lock *fl, unsigned char type);
> >  	void (*lm_break)(struct file_lock *fl);
> >  	int (*lm_change)(struct file_lock **fl, int type);
> >  };

I used variable name "type" because that's what
lm_change uses.  No worries if you think a name
like conflict is better.

The only in-kernel setter of lm_grant is:

fs/lockd/svclock.c:     .lm_grant = nlmsvc_grant_deferred,

and for that, I think using a variable name of
"result" is misleading at best.

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