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From: Johannes Weiner <hannes@cmpxchg.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Stefan Roesch <shr@devkernel.io>,
	kernel-team@fb.com, akpm@linux-foundation.org, riel@surriel.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	stable@vger.kernel.org
Subject: Re: [PATCH v2] mm: Fix for negative counter: nr_file_hugepages
Date: Tue, 7 Nov 2023 15:20:57 -0500	[thread overview]
Message-ID: <20231107202057.GA3798394@cmpxchg.org> (raw)
In-Reply-To: <ZUqZH2jUgrYeCY3z@casper.infradead.org>

On Tue, Nov 07, 2023 at 08:07:59PM +0000, Matthew Wilcox wrote:
> On Tue, Nov 07, 2023 at 03:06:16PM -0500, Johannes Weiner wrote:
> > On Tue, Nov 07, 2023 at 07:35:37PM +0000, Matthew Wilcox wrote:
> > > 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!
> > 
> > Do we need to fix filemap_unaccount_folio() as well?
> 
> Looks to me like it is already correct?
> 
>         __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
>         if (folio_test_swapbacked(folio)) {
>                 __lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
>                 if (folio_test_pmd_mappable(folio))
>                         __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
>         } else if (folio_test_pmd_mappable(folio)) {
>                 __lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
>                 filemap_nr_thps_dec(mapping);
>         }

Argh, I overlooked it because it's nested further in due to that
NR_SHMEM update. Sorry about the noise.


  reply	other threads:[~2023-11-07 20:21 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-07 18:18 Stefan Roesch
2023-11-07 19:35 ` Matthew Wilcox
2023-11-07 20:06   ` Johannes Weiner
2023-11-07 20:07     ` Matthew Wilcox
2023-11-07 20:20       ` Johannes Weiner [this message]
2023-11-08 17:09   ` Stefan Roesch

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