linux-kernel - Re: [PATCH 0/23] File descriptor hot-unplug support v2

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Date:	Mon, 08 Jun 2009 23:42:53 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Miklos Szeredi <miklos@...redi.hu>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	hugh@...itas.com, tj@...nel.org, adobriyan@...il.com,
	alan@...rguk.ukuu.org.uk, gregkh@...e.de, npiggin@...e.de,
	akpm@...ux-foundation.org, hch@...radead.org
Subject: Re: [PATCH 0/23] File descriptor hot-unplug support v2

Linus Torvalds <torvalds@...ux-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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