Re: [Ocfs2-devel] [PATCH v5 03/12] Turn fault_in_pages_{readable, writeable} into fault_in_{readable, writeable}

From: Andreas Gruenbacher <agruenba@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: cluster-devel <cluster-devel@redhat.com>, Jan Kara <jack@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] [PATCH v5 03/12] Turn fault_in_pages_{readable, writeable} into fault_in_{readable, writeable}
Date: Tue, 3 Aug 2021 23:38:12 +0200	[thread overview]
Message-ID: <CAHc6FU7iAPOPO7gtDjpSAVyHwgJ7HQPEhDC_2T__DM8GPW5crQ@mail.gmail.com> (raw)
In-Reply-To: <YQmtnuqDwBIBf4N+@zeniv-ca.linux.org.uk>

On Tue, Aug 3, 2021 at 10:57 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Tue, Aug 03, 2021 at 09:18:09PM +0200, Andreas Gruenbacher wrote:
> > Turn fault_in_pages_{readable,writeable} into versions that return the number
> > of bytes faulted in instead of returning a non-zero value when any of the
> > requested pages couldn't be faulted in.  This supports the existing users that
> > require all pages to be faulted in, but also new users that are happy if any
> > pages can be faulted in.
> >
> > Neither of these functions is entirely trivial and it doesn't seem useful to
> > inline them, so move them to mm/gup.c.
> >
> > Rename the functions to fault_in_{readable,writeable} to make sure that code
> > that uses them can be fixed instead of breaking silently.
>
> Sigh...  We'd already discussed that; it's bloody pointless.  Making short
> fault-in return success - absolutely.  Reporting exact number of bytes is
> not going to be of any use to callers.

I'm not actually convinced that you're right about this. Let's see
what we'll end up with; we can always strip things down in the end.

Thanks,
Andreas

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