Re: [PATCH][0/3] swsusp: use non-contiguous memory

Re: [PATCH][0/3] swsusp: use non-contiguous memory

[Pavel Machek]

Hi!

> The following set of patches is designed to fix a problem in the current
> implementation of swsusp in mainline kernels.  Namely, swsusp uses
> an array of page backup entries (aka pagedir) to store pointers to memory
> pages that must be saved during suspend and restored during resume.
> 
> Unfortunately, the pagedir has to be located in a contiguous chunk of memory
> and it sometimes turns out that an 8-order or even 9-order allocation is needed
> for this purpose.  It sometimes is impossible to get such an allocation and
> swsusp may fail during either suspend or resume due to the lack of memory,
> although theoretically there is enough free memory for it to succeed.
> 
> Moreover, swsusp is more likely to fail for this reason during resume, which
> means that it may fail during resume after a successful suspend
> (this actually has happened for some people, including me :-)) and this,
> potentially, may lead to the loss of data.
> 
> The problem is fixed by replacing the pagedir with a linklist so that
> high-order memory allocations are avoided (the patches make swsusp use only
> 0-order allocations).  Unfortunately this means that it's necessary to change
> assembly routines used to restore the image after it's been loaded from
> swap so that they walk the list instead of walking the array.
> 
> The patches are organized in the following way:
> 
> [1] suspend part
> 	This patch makes swsusp allocate only individual pages during suspend.
> 	It does not require any changes to assembly routines and is
> 	architecture-independent.
> 	It has been present in the -mm kernels for some time.
> 	It contains some additional clean-ups and fixes from Pavel Machek
> 	and Adrian Bunk.
> 
> [2] main resume part (core, i386, x86-64)
> 	This patch makes swsusp allocate only individual pages during resume.
> 	It contains the necessary changes to the assembly routines etc. for i386
> 	and x86-64.
> 	It depends on the suspend part.
> 
> [3] resume part - ppc support
> 	This patch contains the necessary changes to the assembly routines
> 	etc. for ppc.
> 	It depends on the main resume part.
> 	It's a Hu Gang's patch.
> 
> The patches are against 2.6.11.
> 
> Well, I hope I did it right. ;-)  Please consider for applying.

Wow, very nice summary. ACK on all 3 patches...
								Pavel
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