linux-kernel - Re: [PATCH 1/1] suspend: delete sys

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Date:	Fri, 15 May 2015 10:20:16 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	NeilBrown <neilb@...e.de>
cc:	Dave Chinner <david@...morbit.com>, Len Brown <lenb@...nel.org>,
	<rjw@...ysocki.net>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 1/1] suspend: delete sys_sync()

On Fri, 15 May 2015, NeilBrown wrote:

> Some storage devices don't handle suspend as well as they should and lose
> requests resulting in corruption.  They should obviously be fixed, but it is
> you who gets the problem reports and you are not in a position to fix them.
> So you want a general solution that hides those problems.
> sys_sync at suspend time is a sort-of solution because it flushes and waits
> so there  is less in-flight IO immediately after a sys_sync and so less
> opportunity for a bad device to stuff up.
> But you seem to suggest that sys_sync isn't a complete solution and it
> doesn't guarantee that xfs is not doing some background metadata IO.
> 
> Maybe a sensible thing to do would be to hook the "disk" devices into suspend
> and have them flush their queue and possibly send a CACHE_FLUSH command.
> That would provide more of a guarantee for you, and less of a cost for Len,
> would it not?

The sd driver already does this.

Alan Stern

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