From mboxrd@z Thu Jan  1 00:00:00 1970
From: Changli Gao <xiaosuo@gmail.com>
Subject: Re: [PATCH v2 4/4] splice: fix updating sd->pos wrongly
Date: Sat, 29 May 2010 22:22:54 +0800
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Cc: Miklos Szeredi <miklos@szeredi.hu>, axboe@kernel.dk,
	viro@zeniv.linux.org.uk, mszeredi@suse.cz,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
To: Jamie Lokier <jamie@shareable.org>
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In-Reply-To: <20100529140901.GD3106@shareable.org>
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On Sat, May 29, 2010 at 10:09 PM, Jamie Lokier <jamie@shareable.org> wr=
ote:
>
> Not true if the "file" is /dev/mem or /dev/kmem. =C2=A0The starting o=
ffset
> can be negative, so can end at zero.
>
> It's an obscure case and I don't know if you can sendfile from
> /dev/{,k}mem anyway :-) but illustrates why sd->pos !=3D 0 is dubious=
=2E
>

So the safe way is checking if splice_read() updates pos or not, isn't =
it?

if (sd->pos !=3D prev_pos)
    sd->pos =3D prev_pos + ret;


--=20
Regards=EF=BC=8C
Changli Gao(xiaosuo@gmail.com)