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+55aFyej+u+JmWeGZgVECGFQPY909HkDc83+fuC5M1r1HSeHA@mail.gmail.com>
Date:	Tue, 8 Oct 2013 18:38:47 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Al Viro <viro@....linux.org.uk>,
	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 6:18 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> Point, but I would argue that we should yell very loud if we get 0 from
> vfs_write() for non-zero size.  I'm not sure if POSIX allows write(2)
> to return that, but a lot of userland code won't be expecting that and
> won't be able to cope...

Actually POSIX very much allows zero returns. O_NDELAY is mentioned as
a possible cause, in addition to zero-sized writes themselves, of
course.

Also, writing to (but not past) the end of a block device returns 0
for "end of device", iirc.

                Linus
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