linux-kernel - Re: [PATCH] relay: When unsigned ret cannot store a negative value

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Message-Id: <1228278591.10702.5.camel@charm-linux>
Date:	Tue, 02 Dec 2008 22:29:51 -0600
From:	Tom Zanussi <zanussi@...cast.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	roel kluin <roel.kluin@...il.com>, linux-kernel@...r.kernel.org,
	Tom Zanussi <zanussi@...ibm.com>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH] relay: When unsigned ret cannot store a negative value


On Tue, 2008-12-02 at 14:10 -0800, Andrew Morton wrote:
> On Sat, 29 Nov 2008 10:38:06 -0500
> roel kluin <roel.kluin@...il.com> wrote:
> 
> > When unsigned ret cannot store a negative value
> > 
> > Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> > ---
> > UNTESTED! is this the way to go?
> > 
> > diff --git a/kernel/relay.c b/kernel/relay.c
> > index 32b0bef..c9d62e5 100644
> > --- a/kernel/relay.c
> > +++ b/kernel/relay.c
> > @@ -1220,7 +1220,8 @@ static int subbuf_splice_actor(struct file *in,
> >  			       unsigned int flags,
> >  			       int *nonpad_ret)
> >  {
> > -	unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret;
> > +	unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
> > +	ssize_t ret;
> >  	struct rchan_buf *rbuf = in->private_data;
> >  	unsigned int subbuf_size = rbuf->chan->subbuf_size;
> >  	uint64_t pos = (uint64_t) *ppos;
> > @@ -1289,7 +1290,8 @@ static int subbuf_splice_actor(struct file *in,
> >  	if (!spd.nr_pages)
> >  		return 0;
> >  
> > -	ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
> > +	ret = splice_to_pipe(pipe, &spd);
> > +	*nonpad_ret = ret;
> >  	if (ret < 0 || ret < total_len)
> >  		return ret;
> >  
> 
> Yeah, this code needs help.  subbuf_splice_actor() returns `int', but
> carefully calculates and returns an unsigned type.
> 
> I suspect that quite a bit of code in there (including
> relay_file_splice_read()) should be gone through and have its choice of
> types reviewed and fixed.  Probably by converting things to ssize_t.
> 
> 

And maybe generic_file_splice_read() too, from whence it came.  Speaking
of which, is there some reason why this patch:

http://lkml.indiana.edu/hypermail/linux/kernel/0810.3/0094.html

never got picked up?


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