linux-kernel - Re: [PATCH 2/7] mmc: Don't use PF

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Message-ID: <20091117102903.7cb45ff3@lxorguk.ukuu.org.uk>
Date:	Tue, 17 Nov 2009 10:29:03 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	kosaki.motohiro@...fujitsu.com, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mmc@...r.kernel.org
Subject: Re: [PATCH 2/7] mmc: Don't use PF_MEMALLOC

On Tue, 17 Nov 2009 16:17:50 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:

> Non MM subsystem must not use PF_MEMALLOC. Memory reclaim need few
> memory, anyone must not prevent it. Otherwise the system cause
> mysterious hang-up and/or OOM Killer invokation.

So now what happens if we are paging and all our memory is tied up for
writeback to a device or CIFS etc which can no longer allocate the memory
to complete the write out so the MM can reclaim ?

Am I missing something or is this patch set not addressing the case where
the writeback thread needs to inherit PF_MEMALLOC somehow (at least for
the I/O in question and those blocking it)

Alan
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