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Message-ID: <20250901150359.867252-20-david@redhat.com>
Date: Mon,  1 Sep 2025 17:03:40 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: David Hildenbrand <david@...hat.com>,
	Alexander Potapenko <glider@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Brendan Jackman <jackmanb@...gle.com>,
	Christoph Lameter <cl@...two.org>,
	Dennis Zhou <dennis@...nel.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	dri-devel@...ts.freedesktop.org,
	intel-gfx@...ts.freedesktop.org,
	iommu@...ts.linux.dev,
	io-uring@...r.kernel.org,
	Jason Gunthorpe <jgg@...dia.com>,
	Jens Axboe <axboe@...nel.dk>,
	Johannes Weiner <hannes@...xchg.org>,
	John Hubbard <jhubbard@...dia.com>,
	kasan-dev@...glegroups.com,
	kvm@...r.kernel.org,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-arm-kernel@...s.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-crypto@...r.kernel.org,
	linux-ide@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
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	Muchun Song <muchun.song@...ux.dev>,
	netdev@...r.kernel.org,
	Oscar Salvador <osalvador@...e.de>,
	Peter Xu <peterx@...hat.com>,
	Robin Murphy <robin.murphy@....com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Tejun Heo <tj@...nel.org>,
	virtualization@...ts.linux.dev,
	Vlastimil Babka <vbabka@...e.cz>,
	wireguard@...ts.zx2c4.com,
	x86@...nel.org,
	Zi Yan <ziy@...dia.com>
Subject: [PATCH v2 19/37] 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@...hat.com>
---
 mm/gup.c | 25 ++++++++-----------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index c10cd969c1a3b..f0f4d1a68e094 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
@@ -2967,8 +2954,8 @@ 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)
@@ -2989,6 +2976,8 @@ 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;
 }
@@ -3007,8 +2996,8 @@ 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)
@@ -3030,6 +3019,8 @@ 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


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