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

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Message-ID: <alpine.LFD.2.01.0906081217340.6847@localhost.localdomain>
Date:	Mon, 8 Jun 2009 12:18:41 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...IV.linux.org.uk>
cc:	Miklos Szeredi <miklos@...redi.hu>, ebiederm@...ssion.com,
	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



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.

		Linus
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