To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>, Miklos Szeredi <miklos@szeredi.hu>,
       linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
       linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, hugh@veritas.com,
       tj@kernel.org, adobriyan@gmail.com, alan@lxorguk.ukuu.org.uk,
       gregkh@suse.de, npiggin@suse.de, akpm@linux-foundation.org,
       hch@infradead.org
References: <m1skkf761y.fsf@fess.ebiederm.org>
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	<20090608162913.GL8633@ZenIV.linux.org.uk>
	<E1MDhxh-0004nz-Qm@pomaz-ex.szeredi.hu>
	<20090608175018.GM8633@ZenIV.linux.org.uk>
	<alpine.LFD.2.01.0906081100000.6847@localhost.localdomain>
	<20090608185041.GN8633@ZenIV.linux.org.uk>
	<alpine.LFD.2.01.0906081217340.6847@localhost.localdomain>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: Mon, 08 Jun 2009 23:42:53 -0700
In-Reply-To: <alpine.LFD.2.01.0906081217340.6847@localhost.localdomain> (Linus Torvalds's message of "Mon\, 8 Jun 2009 12\:18\:41 -0700 \(PDT\)")
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Linus Torvalds <torvalds@linux-foundation.org> writes:

> On Mon, 8 Jun 2009, Al Viro wrote:
>> 
>> Sure, even though I'm not at all certain that copy_from_user() is that easy.
>> We can make locking current->mm in there interruptible, all right, but that's
>> only a part of the answer - even aside of the allocations, we'd need vma
>> ->fault() interruptible as well, which leads to interruptible instances of
>> ->readpage(), with all the fun _that_ would be.
>
> We already have all that - the NFS people wanted it.
>
> More importantly, you don't actually need to interrupt readpage itself - 
> you just need to stop _waiting_ on it. So in your fault handler, just stop 
> waiting, and instead just return FAULT_RETRY or whatever.

That sounds doable.  Has that code been merged yet?

I took a quick look and it didn't see anyone breaking out of page fault with a
signal or code to really handle that.

Eric
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