linux-kernel - Re: [PATCH 5/7] mm: add new 'orders' parameter for find_get_entries() and find_lock

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Date: Tue, 11 Jun 2024 11:38:31 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, david@...hat.com,
 wangkefeng.wang@...wei.com, chrisl@...nel.org, ying.huang@...el.com,
 21cnbao@...il.com, ryan.roberts@....com, shy828301@...il.com,
 ziy@...dia.com, ioworker0@...il.com, da.gomez@...sung.com,
 p.raghav@...sung.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] mm: add new 'orders' parameter for find_get_entries()
 and find_lock_entries()



On 2024/6/11 00:59, Matthew Wilcox wrote:
> On Thu, Jun 06, 2024 at 07:58:55PM +0800, Baolin Wang wrote:
>> In the following patches, shmem will support the swap out of large folios,
>> which means the shmem mappings may contain large order swap entries, so an
>> 'orders' array is added for find_get_entries() and find_lock_entries() to
>> obtain the order size of shmem swap entries, which will help in the release
>> of shmem large folio swap entries.
> 
> I am not a fan.

With Daniel's suggestion, I think I can drop the 'order' parameter if 
you don't like it.

I was hoping that 'order' would be encoded in the swap
> entry, not passed as a separate parameter.
> 
> As I understand it, we currently have a free bit, or
> swp_to_radix_entry() would not work.  We can use that as detailed
> here to encode the order in a single bit.
> 
> https://kernelnewbies.org/MatthewWilcox/NaturallyAlignedOrder

OK. This seems to deserve a separate patch set. I will look at your 
suggestion in detail. Thanks.