linux-kernel - Re: [PATCH] readahead: Use folio_nr_pages() instead of shift operation

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Message-Id: <20250712152544.07f236ec277290c70a2a862f@linux-foundation.org>
Date: Sat, 12 Jul 2025 15:25:44 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Chi Zhiling <chizhiling@....com>
Cc: David Hildenbrand <david@...hat.com>, willy@...radead.org,
 linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Chi Zhiling <chizhiling@...inos.cn>, Ryan
 Roberts <ryan.roberts@....com>
Subject: Re: [PATCH] readahead: Use folio_nr_pages() instead of shift
 operation

On Sat, 12 Jul 2025 10:23:32 +0800 Chi Zhiling <chizhiling@....com> wrote:

> On 2025/7/12 00:15, David Hildenbrand wrote:
> > On 10.07.25 08:04, Chi Zhiling wrote:
> >> From: Chi Zhiling <chizhiling@...inos.cn>
> >>
> >> folio_nr_pages() is faster helper function to get the number of pages
> >> when NR_PAGES_IN_LARGE_FOLIO is enabled.
> >>
> >> Signed-off-by: Chi Zhiling <chizhiling@...inos.cn>
> >> ---
> >>   mm/readahead.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/mm/readahead.c b/mm/readahead.c
> >> index 95a24f12d1e7..406756d34309 100644
> >> --- a/mm/readahead.c
> >> +++ b/mm/readahead.c
> >> @@ -649,7 +649,7 @@ void page_cache_async_ra(struct readahead_control 
> >> *ractl,
> >>        * Ramp up sizes, and push forward the readahead window.
> >>        */
> >>       expected = round_down(ra->start + ra->size - ra->async_size,
> >> -            1UL << folio_order(folio));
> >> +            folio_nr_pages(folio));
> >>       if (index == expected) {
> >>           ra->start += ra->size;
> >>           /*
> > 
> > This should probably get squashed in Ryans commit?
> 
> I have no objection, it's up to Ryan.

"Ryans commit" is now c4602f9fa77f ("mm/readahead: store folio order in
struct file_ra_state") in mm-stable.  I'd prefer not to rebase for this!