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mm: gup: cleanup gup_fast call chain

PATCH Applied Aristeu Rozanski 2 participants 5 messages Aug 28 – Sep 19

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Aristeu Rozanski

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#0 lore raw

v3 cover mm: gup: cleanup gup_fast call chain

These two patches implement the refactor in gup_fast call chain David Hildenbrand mentioned in

	https://lore.kernel.org/all/[email protected]/T/#u

v2: removed unneeded initializations on the second patch as pointed by David
v3: fixed gup_fast_pmd_range() nr_pages initialization as pointed by David

Suggested-by David Hildenbrand <[email protected]>
Link https://lore.kernel.org/all/[email protected]/T/#u open here
Cc Andrew Morton <[email protected]>
Cc David Hildenbrand <[email protected]>
Cc Jason Gunthorpe <[email protected]>
Cc John Hubbard <[email protected]>
Cc Peter Xu <[email protected]>
Signed-off-by Aristeu Rozanski <[email protected]>
Signature · 1 line
Aristeu
author
#1 lore raw

PATCH v3 1/2 mm: gup: move pmd_protnone() into gup_fast_pmd_leaf()

Make pmd handling match pud handling by calling pmd_protnone() inside gup_fast_pmd_leaf().

Suggested-by David Hildenbrand <[email protected]>
Link https://lore.kernel.org/all/[email protected]/T/#u open here
Cc Andrew Morton <[email protected]>
Cc David Hildenbrand <[email protected]>
Cc Jason Gunthorpe <[email protected]>
Cc John Hubbard <[email protected]>
Cc Peter Xu <[email protected]>
Signed-off-by Aristeu Rozanski <[email protected]>
---
 mm/gup.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
mm/gup.c +4 -4
@@ -2929,6 +2929,10 @@ static int gup_fast_pmd_leaf(pmd_t orig,
 	struct folio *folio;
 	int refs;
 
+	/* See gup_fast_pte_range() */
+	if (pmd_protnone(orig))
+		return 0;
+
 	if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
 		return 0;
 

@@ -3024,10 +3028,6 @@ static int gup_fast_pmd_range(pud_t *pud
 			return 0;
 
 		if (unlikely(pmd_leaf(pmd))) {
-			/* See gup_fast_pte_range() */
-			if (pmd_protnone(pmd))
-				return 0;
-
 			if (!gup_fast_pmd_leaf(pmd, pmdp, addr, next, flags,
 				pages, nr))
 				return 0;
author
#2 lore raw

PATCH v3 2/2 mm: gup: cleanup the gup_fast_*() call chain

In reply to Aristeu Rozanski

Refactor gup_fast functions so each step of the way returns the number of pages pinned. Because the previous step of the chain knows what the number it should be, less indicates an error. This way there's no need to pass *nr along.

Suggested-by David Hildenbrand <[email protected]>
Link https://lore.kernel.org/all/[email protected]/T/#u open here
Cc Andrew Morton <[email protected]>
Cc David Hildenbrand <[email protected]>
Cc Jason Gunthorpe <[email protected]>
Cc John Hubbard <[email protected]>
Cc Peter Xu <[email protected]>
Signed-off-by Aristeu Rozanski <[email protected]>
---
 mm/gup.c |  179 +++++++++++++++++++++++++++++++++------------------------------
 1 file changed, 94 insertions(+), 85 deletions(-)
mm/gup.c +94 -85
@@ -2826,11 +2826,11 @@ static bool gup_fast_folio_allowed(struc
  * also check pmd here to make sure pmd doesn't change (corresponds to
  * pmdp_collapse_flush() in the THP collapse code path).
  */
-static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
+static unsigned long gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp,
+		unsigned long addr, unsigned long end,
+		unsigned int flags, struct page **pages)
 {
-	int ret = 0;
+	unsigned long nr_pages = 0;
 	pte_t *ptep, *ptem;
 
 	ptem = ptep = pte_offset_map(&pmd, addr);

@@ -2892,15 +2892,13 @@ static int gup_fast_pte_range(pmd_t pmd,
 			goto pte_unmap;
 		}
 		folio_set_referenced(folio);
-		pages[*nr] = page;
-		(*nr)++;
+		pages[nr_pages] = page;
+		nr_pages++;
 	} while (ptep++, addr += PAGE_SIZE, addr != end);
 
-	ret = 1;
-
 pte_unmap:
 	pte_unmap(ptem);
-	return ret;
+	return nr_pages;
 }
 #else
 

@@ -2913,21 +2911,21 @@ pte_unmap:
  * get_user_pages_fast_only implementation that can pin pages. Thus it's still
  * useful to have gup_fast_pmd_leaf even if we can't operate on ptes.
  */
-static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
+static unsigned long gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp,
+		unsigned long addr, unsigned long end,
+		unsigned int flags, struct page **pages)
 {
 	return 0;
 }
 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 
-static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
+static unsigned long gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp,
+		unsigned long addr, unsigned long end,
+		unsigned int flags, struct page **pages)
 {
 	struct page *page;
 	struct folio *folio;
-	int refs;
+	unsigned long nr_pages, i;
 
 	/* See gup_fast_pte_range() */
 	if (pmd_protnone(orig))

@@ -2939,42 +2937,40 @@ static int gup_fast_pmd_leaf(pmd_t orig,
 	if (pmd_special(orig))
 		return 0;
 
-	refs = (end - addr) >> PAGE_SHIFT;
+	nr_pages = (end - addr) >> PAGE_SHIFT;
 	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 
-	folio = try_grab_folio_fast(page, refs, flags);
+	folio = try_grab_folio_fast(page, nr_pages, flags);
 	if (!folio)
 		return 0;
 
 	if (unlikely(pmd_val(orig) != pmd_val(pmdp_get_lockless(pmdp)))) {
-		gup_put_folio(folio, refs, flags);
+		gup_put_folio(folio, nr_pages, flags);
 		return 0;
 	}
 
 	if (!gup_fast_folio_allowed(folio, flags)) {
-		gup_put_folio(folio, refs, flags);
+		gup_put_folio(folio, nr_pages, flags);
 		return 0;
 	}
 	if (!pmd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
-		gup_put_folio(folio, refs, flags);
+		gup_put_folio(folio, nr_pages, flags);
 		return 0;
 	}
 
-	pages += *nr;
-	*nr += refs;
-	for (; refs; refs--)
+	for (i = 0; i < nr_pages; i++)
 		*(pages++) = page++;
 	folio_set_referenced(folio);
-	return 1;
+	return nr_pages;
 }
 
-static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
+static unsigned long gup_fast_pud_leaf(pud_t orig, pud_t *pudp,
+		unsigned long addr, unsigned long end,
+		unsigned int flags, struct page **pages)
 {
 	struct page *page;
 	struct folio *folio;
-	int refs;
+	unsigned long nr_pages, i;
 
 	if (!pud_access_permitted(orig, flags & FOLL_WRITE))
 		return 0;

@@ -2982,41 +2978,39 @@ static int gup_fast_pud_leaf(pud_t orig,
 	if (pud_special(orig))
 		return 0;
 
-	refs = (end - addr) >> PAGE_SHIFT;
+	nr_pages = (end - addr) >> PAGE_SHIFT;
 	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 
-	folio = try_grab_folio_fast(page, refs, flags);
+	folio = try_grab_folio_fast(page, nr_pages, flags);
 	if (!folio)
 		return 0;
 
 	if (unlikely(pud_val(orig) != pud_val(pudp_get(pudp)))) {
-		gup_put_folio(folio, refs, flags);
+		gup_put_folio(folio, nr_pages, flags);
 		return 0;
 	}
 
 	if (!gup_fast_folio_allowed(folio, flags)) {
-		gup_put_folio(folio, refs, flags);
+		gup_put_folio(folio, nr_pages, flags);
 		return 0;
 	}
 
 	if (!pud_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
-		gup_put_folio(folio, refs, flags);
+		gup_put_folio(folio, nr_pages, flags);
 		return 0;
 	}
 
-	pages += *nr;
-	*nr += refs;
-	for (; refs; refs--)
+	for (i = 0; i < nr_pages; i++)
 		*(pages++) = page++;
 	folio_set_referenced(folio);
-	return 1;
+	return nr_pages;
 }
 
-static int gup_fast_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
+static unsigned long gup_fast_pmd_range(pud_t *pudp, pud_t pud,
+		unsigned long addr, unsigned long end,
+		unsigned int flags, struct page **pages)
 {
-	unsigned long next;
+	unsigned long next, nr_pages = 0, chunk_nr_pages;
 	pmd_t *pmdp;
 
 	pmdp = pmd_offset_lockless(pudp, pud, addr);

@@ -3025,26 +3019,30 @@ static int gup_fast_pmd_range(pud_t *pud
 
 		next = pmd_addr_end(addr, end);
 		if (!pmd_present(pmd))
-			return 0;
+			break;
 
 		if (unlikely(pmd_leaf(pmd))) {
-			if (!gup_fast_pmd_leaf(pmd, pmdp, addr, next, flags,
-				pages, nr))
-				return 0;
-
-		} else if (!gup_fast_pte_range(pmd, pmdp, addr, next, flags,
-					       pages, nr))
-			return 0;
+			chunk_nr_pages = gup_fast_pmd_leaf(pmd, pmdp, addr,
+							   next, flags,
+							   &pages[nr_pages]);
+
+		} else
+			chunk_nr_pages = gup_fast_pte_range(pmd, pmdp, addr,
+							    next, flags,
+							    &pages[nr_pages]);
+		nr_pages += chunk_nr_pages;
+		if (chunk_nr_pages != (next - addr) >> PAGE_SHIFT)
+			break;
 	} while (pmdp++, addr = next, addr != end);
 
-	return 1;
+	return nr_pages;
 }
 
-static int gup_fast_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
+static unsigned long gup_fast_pud_range(p4d_t *p4dp, p4d_t p4d,
+		unsigned long addr, unsigned long end,
+		unsigned int flags, struct page **pages)
 {
-	unsigned long next;
+	unsigned long next, nr_pages = 0, chunk_nr_pages;
 	pud_t *pudp;
 
 	pudp = pud_offset_lockless(p4dp, p4d, addr);

@@ -3053,24 +3051,27 @@ static int gup_fast_pud_range(p4d_t *p4d
 
 		next = pud_addr_end(addr, end);
 		if (unlikely(!pud_present(pud)))
-			return 0;
-		if (unlikely(pud_leaf(pud))) {
-			if (!gup_fast_pud_leaf(pud, pudp, addr, next, flags,
-					       pages, nr))
-				return 0;
-		} else if (!gup_fast_pmd_range(pudp, pud, addr, next, flags,
-					       pages, nr))
-			return 0;
+			break;
+		if (unlikely(pud_leaf(pud)))
+			chunk_nr_pages = gup_fast_pud_leaf(pud, pudp, addr,
+							   next, flags,
+							   &pages[nr_pages]);
+		else
+			chunk_nr_pages = gup_fast_pmd_range(pudp, pud, addr,
+							    next, flags,
+							    &pages[nr_pages]);
+		nr_pages += chunk_nr_pages;
+		if (chunk_nr_pages != (next - addr) >> PAGE_SHIFT)
+			break;
 	} while (pudp++, addr = next, addr != end);
 
-	return 1;
+	return nr_pages;
 }
 
-static int gup_fast_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
-		unsigned long end, unsigned int flags, struct page **pages,
-		int *nr)
+static unsigned long gup_fast_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,
+		unsigned long end, unsigned int flags, struct page **pages)
 {
-	unsigned long next;
+	unsigned long next, nr_pages = 0, chunk_nr_pages;
 	p4d_t *p4dp;
 
 	p4dp = p4d_offset_lockless(pgdp, pgd, addr);

@@ -3079,20 +3080,23 @@ static int gup_fast_p4d_range(pgd_t *pgd
 
 		next = p4d_addr_end(addr, end);
 		if (!p4d_present(p4d))
-			return 0;
+			break;
 		BUILD_BUG_ON(p4d_leaf(p4d));
-		if (!gup_fast_pud_range(p4dp, p4d, addr, next, flags,
-					pages, nr))
-			return 0;
+		chunk_nr_pages = gup_fast_pud_range(p4dp, p4d, addr, next,
+						    flags, &pages[nr_pages]);
+		nr_pages += chunk_nr_pages;
+		if (chunk_nr_pages != (next - addr) >> PAGE_SHIFT)
+			break;
 	} while (p4dp++, addr = next, addr != end);
 
-	return 1;
+	return nr_pages;
 }
 
-static void gup_fast_pgd_range(unsigned long addr, unsigned long end,
-		unsigned int flags, struct page **pages, int *nr)
+static unsigned long gup_fast_pgd_range(unsigned long addr,
+		unsigned long end, unsigned int flags,
+		struct page **pages)
 {
-	unsigned long next;
+	unsigned long next, nr_pages = 0, chunk_nr_pages;
 	pgd_t *pgdp;
 
 	pgdp = pgd_offset(current->mm, addr);

@@ -3101,17 +3105,23 @@ static void gup_fast_pgd_range(unsigned
 
 		next = pgd_addr_end(addr, end);
 		if (pgd_none(pgd))
-			return;
+			break;
 		BUILD_BUG_ON(pgd_leaf(pgd));
-		if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags,
-					pages, nr))
-			return;
+		chunk_nr_pages = gup_fast_p4d_range(pgdp, pgd, addr, next,
+						    flags, &pages[nr_pages]);
+		nr_pages += chunk_nr_pages;
+		if (chunk_nr_pages != (next - addr) >> PAGE_SHIFT)
+			break;
 	} while (pgdp++, addr = next, addr != end);
+
+	return nr_pages;
 }
 #else
-static inline void gup_fast_pgd_range(unsigned long addr, unsigned long end,
-		unsigned int flags, struct page **pages, int *nr)
+static inline unsigned long gup_fast_pgd_range(unsigned long addr,
+		unsigned long end, unsigned int flags,
+		struct page **pages)
 {
+	return 0;
 }
 #endif /* CONFIG_HAVE_GUP_FAST */
 

@@ -3129,8 +3139,7 @@ static bool gup_fast_permitted(unsigned
 static unsigned long gup_fast(unsigned long start, unsigned long end,
 		unsigned int gup_flags, struct page **pages)
 {
-	unsigned long flags;
-	int nr_pinned = 0;
+	unsigned long flags, nr_pinned;
 	unsigned seq;
 
 	if (!IS_ENABLED(CONFIG_HAVE_GUP_FAST) ||

@@ -3154,7 +3163,7 @@ static unsigned long gup_fast(unsigned l
 	 * that come from callers of tlb_remove_table_sync_one().
 	 */
 	local_irq_save(flags);
-	gup_fast_pgd_range(start, end, gup_flags, pages, &nr_pinned);
+	nr_pinned = gup_fast_pgd_range(start, end, gup_flags, pages);
 	local_irq_restore(flags);
 
 	/*
maintainer Acked-by on the v3 series
#3 lore raw
In reply to Aristeu Rozanski
Quoted 8 lines · Aristeu Rozanski

These two patches implement the refactor in gup_fast call chain David Hildenbrand mentioned in

	https://lore.kernel.org/all/[email protected]/T/#u

v2: removed unneeded initializations on the second patch as pointed by David
v3: fixed gup_fast_pmd_range() nr_pages initialization as pointed by David

Quoted 9 lines
Suggested-by David Hildenbrand <[email protected]>
Link https://lore.kernel.org/all/[email protected]/T/#u open here
Cc Andrew Morton <[email protected]>
Cc David Hildenbrand <[email protected]>
Cc Jason Gunthorpe <[email protected]>
Cc John Hubbard <[email protected]>
Cc Peter Xu <[email protected]>
Signed-off-by Aristeu Rozanski <[email protected]>
Acked-by David Hildenbrand (Arm) <[email protected]>

Andrew, can you queue this? If I manage to set up the new component flow on my side fairly quickly, I might still pick this my self.

(have to dig through tons of mail first before getting started on that)

Signature · 3 lines
Cheers,

David
maintainer Applied
#4 lore raw
In reply to Aristeu Rozanski
Quoted 9 lines · Aristeu Rozanski

These two patches implement the refactor in gup_fast call chain David Hildenbrand mentioned in

	https://lore.kernel.org/all/[email protected]/T/#u

v2: removed unneeded initializations on the second patch as pointed by David
v3: fixed gup_fast_pmd_range() nr_pages initialization as pointed by David

[...]

Applied, thanks!

tree: mm/core.git
branch: gup-7.4.misc

Applied patches will appear soon in mm-next, followed by linux-next.

Please report any outstanding bugs that were missed during review, so we can either drop the patch series or decide how to fix it up.

It is encouraged to provide Acked-bys, Reviewed-bys, and Tested-bys even though the patches have already been applied. If possible, patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. Further, this is not a guarantee that the patches will go upstream. If in doubt, please check the listed branch.

[1/2] mm: gup: move pmd_protnone() into gup_fast_pmd_leaf()

      https://git.kernel.org/mm/core/c/9ad472cf
[2/2] mm: gup: cleanup the gup_fast_*() call chain
      https://git.kernel.org/mm/core/c/49f7113d
Signature · 3 lines
Cheers,

David