linux-kernel - Re: [PATCH]: Compress hibernation image with LZO (in-kernel)

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Date:	Sat, 31 Jul 2010 11:03:04 +1000
From:	Bojan Smojver <bojan@...ursive.com>
To:	Nigel Cunningham <nigel@...onice.net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH]: Compress hibernation image with LZO (in-kernel)

On Sat, 2010-07-31 at 09:40 +1000, Nigel Cunningham wrote:

> How about vmallocing the cmp as well? That would greatly reduce the 
> potential for page allocation failures while still letting you use an 
> order 6 area.

In save_image(), that worked. In load_image() it would cause a crash
(something about kernel not being able to satisfy paging request). So, I
just made it __get_free_pages() instead. But, yeah good point.

Keep in mind that I have absolutely no idea how kernel memory allocation
works. I'm kinda coping and pasting code and hoping it doesn't crash :-)

> > PS. I guess with this, read_sync can simply disappear as well.
> 
> I haven't looked at the code for a while, but it might still be needed 
> for the header? I know that in TuxOnIce, I need to read the first page 
> synchronously when bootstrapping reading the image (can't read the next 
> page until you know where it is, and its location is on the first page). 
> Since swsusp uses those index pages, I think it would have the same 
> issue - they would need to be read before it could read the following 
> pages. Of course I'm going off memory :)

I think it can go, because the header is already read/written with &bio
set to NULL (sync read). See patch to remove read_sync.

-- 
Bojan

View attachment "hibernate-no-sync_read.patch" of type "text/x-patch" (1519 bytes)