linux-kernel - Re: [PATCH] libata, freezer: avoid block device removal while system is frozen

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Message-ID: <CACVXFVMPQUjAmvNpO+WVLDzVBwkwPtqqyBga_uXxfptVpEPPbw@mail.gmail.com>
Date:	Mon, 16 Dec 2013 21:24:40 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Nigel Cunningham <nigel@...elcunningham.com.au>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Jens Axboe <axboe@...nel.dk>, tomaz.solc@...lix.org,
	aaron.lu@...el.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH] libata, freezer: avoid block device removal while system
 is frozen

On Mon, Dec 16, 2013 at 8:45 PM, Tejun Heo <tj@...nel.org> wrote:
> Hello,
>
> On Mon, Dec 16, 2013 at 08:12:07PM +0800, Ming Lei wrote:
>> Looks we should guarantee that I/O queue is emptied before system sleep,
>> otherwise it may be a bug, since battery may be drained up to cause
>> data loss or block devices may be disconnected during sleep.
>
> It's a bit beside the point as that's what journaling is for.  Power
> loss during suspend isn't all that different from power loss while
> suspended.  Also, the filesystems are already synced before entering
> suspend, so it shouldn't be an issue.  However, that doesn't guarantee
> there aren't no pending bdi work items.  We *hope* to control the

You mean there are still some write I/O scheduled after processes are
frozen? by unfreezable kernel threads?

> sources with freezer but there's no guarantee about the coverage and
> no way to verify that either.

Thanks,
-- 
Ming Lei
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