Re: [PATCH v7 0/6] solve deadlock caused by memory allocation withI/O

[Andrew Morton]

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