The nice thing is that we only record pages in the array if they actually passed our tests.
Yeah that's nice actually.
This is fine (not the meme :P)
:D
So yes let's do this!
That leaves us with the following on top of this patch:
From 4533c6e3590cab0c53e81045624d5949e0ad9015 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@xxxxxxxxxx>
Date: Fri, 29 Aug 2025 15:41:45 +0200
Subject: [PATCH] mm/gup: remove record_subpages()
We can just cleanup the code by calculating the #refs earlier,
so we can just inline what remains of record_subpages().
Calculate the number of references/pages ahead of times, and record them
only once all our tests passed.
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
mm/gup.c | 25 ++++++++-----------------
1 file changed, 8 insertions(+), 17 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index 89ca0813791ab..5a72a135ec70b 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -484,19 +484,6 @@ static inline void mm_set_has_pinned_flag(struct mm_struct *mm)
#ifdef CONFIG_MMU
#ifdef CONFIG_HAVE_GUP_FAST
-static int record_subpages(struct page *page, unsigned long sz,
- unsigned long addr, unsigned long end,
- struct page **pages)
-{
- int nr;
-
- page += (addr & (sz - 1)) >> PAGE_SHIFT;
- for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
- pages[nr] = page++;
-
- return nr;
-}
-
/**
* try_grab_folio_fast() - Attempt to get or pin a folio in fast path.
* @page: pointer to page to be grabbed
@@ -2963,8 +2950,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
if (pmd_special(orig))
return 0;
- page = pmd_page(orig);
- refs = record_subpages(page, PMD_SIZE, addr, end, pages + *nr);
+ refs = (end - addr) >> PAGE_SHIFT;
+ page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
folio = try_grab_folio_fast(page, refs, flags);
if (!folio)
@@ -2985,6 +2972,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
}
*nr += refs;
+ for (; refs; refs--)
+ *(pages++) = page++;
folio_set_referenced(folio);
return 1;
}
@@ -3003,8 +2992,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
if (pud_special(orig))
return 0;
- page = pud_page(orig);
- refs = record_subpages(page, PUD_SIZE, addr, end, pages + *nr);
+ refs = (end - addr) >> PAGE_SHIFT;
+ page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
folio = try_grab_folio_fast(page, refs, flags);
if (!folio)
@@ -3026,6 +3015,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
}
*nr += refs;
+ for (; refs; refs--)
+ *(pages++) = page++;
folio_set_referenced(folio);
return 1;
}
--
2.50.1
--
Cheers
David / dhildenb
