linux-kernel - Re: [PATCH v2] mm: Fix for negative counter: nr_file

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Date:   Wed, 08 Nov 2023 09:09:55 -0800
From:   Stefan Roesch <shr@...kernel.io>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     kernel-team@...com, akpm@...ux-foundation.org, hannes@...xchg.org,
        riel@...riel.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] mm: Fix for negative counter: nr_file_hugepages


Matthew Wilcox <willy@...radead.org> writes:

> On Tue, Nov 07, 2023 at 10:18:05AM -0800, Stefan Roesch wrote:
>> +++ b/mm/huge_memory.c
>> @@ -2740,7 +2740,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
>>  			if (folio_test_swapbacked(folio)) {
>>  				__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS,
>>  							-nr);
>> -			} else {
>> +			} else if (folio_test_pmd_mappable(folio)) {
>>  				__lruvec_stat_mod_folio(folio, NR_FILE_THPS,
>>  							-nr);
>>  				filemap_nr_thps_dec(mapping);
>
> As I said, we also need the folio_test_pmd_mappable() for swapbacked.
> Not because there's currently a problem, but because we don't leave
> landmines for other people to trip over in future!

I'll add it in the next version.