linux-kernel - Re: [PATCH v7 0/6] solve deadlock caused by memory allocation with I/O

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Message-Id: <20130116153744.70210fa3.akpm@linux-foundation.org>
Date:	Wed, 16 Jan 2013 15:37:44 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-mm@...ck.org, Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>,
	Minchan Kim <minchan@...nel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Jens Axboe <axboe@...nel.dk>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v7 0/6] solve deadlock caused by memory allocation with
 I/O

On Sat,  5 Jan 2013 10:25:38 +0800
Ming Lei <ming.lei@...onical.com> wrote:

> This patchset try to solve one deadlock problem which might be caused
> by memory allocation with block I/O during runtime PM and block device
> error handling path. Traditionly, the problem is addressed by passing
> GFP_NOIO statically to mm, but that is not a effective solution, see
> detailed description in patch 1's commit log.
> 
> This patch set introduces one process flag and trys to fix the deadlock
> problem on block device/network device during runtime PM or usb bus reset.

The patchset doesn't look like the worst thing I've ever applied ;)

One thing I'm wondering: during suspend and resume, why are GFP_KERNEL
allocation attempts even getting down to the device layer?  Presumably
the page scanner is encountering dirty pagecache or dirty swapcache
pages?

If so, I wonder if we could avoid the whole problem by appropriately
syncing all dirty memory back to storage before starting to turn devices
off?

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