linux-kernel - Re: [RFC][PATCH 10/13] make dump_emit() use vfs_write() instead of banging at ->f

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Message-ID: <CA+55aFxvNhuXoux88tcYemMWe5Nxdc-srfj3YgBZ7LJ-JaBEdQ@mail.gmail.com>
Date:	Tue, 8 Oct 2013 17:52:42 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@....linux.org.uk>
Cc:	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 10/13] make dump_emit() use vfs_write() instead of
 banging at ->f_op->write directly

On Tue, Oct 8, 2013 at 5:15 PM, Al Viro <viro@....linux.org.uk> wrote:
>
> ... and deal with short writes properly

.. except you don't.

> +       while (nr) {
> +               if (dump_interrupted())
> +                       return 0;
> +               n = vfs_write(file, addr, nr, &pos);
> +               if (n < 0)
> +                       return 0;
> +               file->f_pos = pos;
> +               cprm->written += n;
> +               nr -= n;
> +       }

Please handle 'n == 0' too. Maybe it never happens (ie you get EPIPE
or ENOSPC), but write returning zero is actually possible and a valid
return value and traditional for "end of media". Looping forever is
not a good idea.

               Linus
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