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Message-ID: <Zl243qf2WiPHIMWN@casper.infradead.org>
Date: Mon, 3 Jun 2024 13:36:46 +0100
From: Matthew Wilcox <willy@...radead.org>
To: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
Cc: david@...morbit.com, chandan.babu@...cle.com, akpm@...ux-foundation.org,
brauner@...nel.org, djwong@...nel.org, linux-kernel@...r.kernel.org,
hare@...e.de, john.g.garry@...cle.com, gost.dev@...sung.com,
yang@...amperecomputing.com, p.raghav@...sung.com,
cl@...amperecomputing.com, linux-xfs@...r.kernel.org, hch@....de,
mcgrof@...nel.org, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v6 05/11] mm: split a folio in minimum folio order chunks
On Wed, May 29, 2024 at 03:45:03PM +0200, Pankaj Raghav (Samsung) wrote:
> @@ -3572,14 +3600,19 @@ static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
>
> for (index = off_start; index < off_end; index += nr_pages) {
> struct folio *folio = filemap_get_folio(mapping, index);
> + unsigned int min_order, target_order = new_order;
>
> nr_pages = 1;
> if (IS_ERR(folio))
> continue;
>
> - if (!folio_test_large(folio))
> + if (!folio->mapping || !folio_test_large(folio))
> goto next;
This check is useless. folio->mapping is set to NULL on truncate,
but you haven't done anything to prevent truncate yet. That happens
later when you lock the folio.
> + min_order = mapping_min_folio_order(mapping);
You should hoist this out of the loop.
> + if (new_order < min_order)
> + target_order = min_order;
> +
> total++;
> nr_pages = folio_nr_pages(folio);
>
> @@ -3589,7 +3622,18 @@ static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
> if (!folio_trylock(folio))
> goto next;
>
> - if (!split_folio_to_order(folio, new_order))
> + if (!folio_test_anon(folio)) {
Please explain how a folio _in a file_ can be anon?
> + unsigned int min_order;
> +
> + if (!folio->mapping)
> + goto next;
> +
> + min_order = mapping_min_folio_order(folio->mapping);
> + if (new_order < target_order)
> + target_order = min_order;
Why is this being repeated?
> + }
> +
> + if (!split_folio_to_order(folio, target_order))
> split++;
>
> folio_unlock(folio);
> --
> 2.34.1
>
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