Re: [RFC] iommu: Use put_pages_list

[Robin Murphy <robin.murphy@arm.com>]

On 2021-10-14 12:52, John Garry wrote:
> On 14/10/2021 12:20, Matthew Wilcox wrote:
>> I'm going to keep pinging this patch weekly.
>>
>> On Thu, Oct 07, 2021 at 07:17:02PM +0100, Matthew Wilcox wrote:
>>> ping?
> 
> Robin, Were you checking this? You mentioned "I got
> side-tracked trying to make io-pgtable use that freelist properly" in 
> another thread, which seems related.

Ooh, thanks for the heads-up John - I'm still only just starting to 
catch up on my mailing list folders since I got back off holiday.

Indeed I already started untangling the freelist handling in the flush 
queue code (to make the move into iommu-dma smaller). Once I'd figured 
out how it worked I did wonder whether there was any more "standard" 
field to borrow, since page->freelist did seem very much in the 
minority. If page->lru is it then great! From a quick skim of the patch 
I think I'd only have a few trivial review comments to make - certainly 
no objection to the fundamental change itself (indeed I hit a point in 
io-pgtable-arm where adding to the pointer chain got rather awkward, so 
having proper lists to splice would be lovely).

Matthew - is this something getting in the way of mm development, or 
just a nice cleanup? I'd be happy either to pursue merging it on its 
own, or to pick it up and work it into a series with my stuff.

Cheers,
Robin.

> 
> Thanks,
> John
> 
>>>
>>> On Thu, Sep 30, 2021 at 05:20:42PM +0100, Matthew Wilcox (Oracle) wrote:
>>>> page->freelist is for the use of slab.  We already have the ability
>>>> to free a list of pages in the core mm, but it requires the use of a
>>>> list_head and for the pages to be chained together through page->lru.
>>>> Switch the iommu code over to using free_pages_list().
>>>>
>>>> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
>>>> ---
>>>>   drivers/iommu/amd/io_pgtable.c | 99 
>>>> +++++++++++++++-------------------
>>>>   drivers/iommu/dma-iommu.c      | 11 +---
>>>>   drivers/iommu/intel/iommu.c    | 89 +++++++++++-------------------
>>>>   include/linux/iommu.h          |  3 +-
>>>>   4 files changed, 77 insertions(+), 125 deletions(-)
>>>>
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