linux-kernel - Re: [PATCH v2 4/4] splice: fix updating sd->pos wrongly

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Message-ID: <AANLkTinBmZej_rQFQ_bMPJf9GGJFFW3zdnpqZTXZCIfc@mail.gmail.com>
Date:	Fri, 28 May 2010 19:36:36 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	axboe@...nel.dk, viro@...iv.linux.org.uk, mszeredi@...e.cz,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] splice: fix updating sd->pos wrongly

On Fri, May 28, 2010 at 7:11 PM, Miklos Szeredi <miklos@...redi.hu> wrote:
> On Fri, 28 May 2010, Changli Gao wrote:
>>  Before checking the sd->pos, sd->pos
>> already is updated with the value returned by splice_read(), so if in
>> file is seekabble, sd->pos is non-zero when I checking it.
>
> I see the logic now.  But it's really confusing, at least some
> comments would be needed.
>
> But I think it would be better not to try reusing sd->pos for reading,
> but supplying an "loff_t *read_ppos" to splice_direct_to_actor and
> leaving sd->pos alone (for the write side to use and update as
> necessary).
>

               if (ret < read_len) {

I think is much like a hack too. :)

-                       sd->pos = prev_pos + ret;
+                       if (sd->pos)
+                               sd->pos = prev_pos + ret;
                       goto out_release;
               }

Anyway, it can fix the issue I mentioned above. Any future cleanup
should not be mixed in, IMO.

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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