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From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: David Hildenbrand <david@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Rapoport <rppt@kernel.org>,
	Jason Gunthorpe <jgg@nvidia.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Peter Xu <peterx@redhat.com>,
	linux-arm-kernel@lists.infradead.org,
	loongarch@lists.linux.dev,
	linux-mips@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org,
	linux-sh@vger.kernel.org,
	linux-mm@kvack.org,
	linux-perf-users@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	x86@kernel.org
Subject: [PATCH RFC 1/3] mm/gup: consistently name GUP-fast functions
Date: Wed, 27 Mar 2024 14:05:36 +0100
Message-ID: <20240327130538.680256-2-david@redhat.com>
In-Reply-To: <20240327130538.680256-1-david@redhat.com>
References: <20240327130538.680256-1-david@redhat.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Let's consistently call the "fast-only" part of GUP "GUP-fast" and rename
all relevant internal functions to start with "gup_fast", to make it
clearer that this is not ordinary GUP. The current mixture of
"lockless", "gup" and "gup_fast" is confusing.

Further, avoid the term "huge" when talking about a "leaf" -- for
example, we nowadays check pmd_leaf() because pmd_huge() is gone. For the
"hugepd"/"hugepte" stuff, it's part of the name ("is_hugepd"), so that
says.

What remains is the "external" interface:
* get_user_pages_fast_only()
* get_user_pages_fast()
* pin_user_pages_fast()

And the "internal" interface that handles GUP-fast + fallback:
* internal_get_user_pages_fast()

The high-level internal function for GUP-fast is now:
* gup_fast()

The basic GUP-fast walker functions:
* gup_pgd_range() -> gup_fast_pgd_range()
* gup_p4d_range() -> gup_fast_p4d_range()
* gup_pud_range() -> gup_fast_pud_range()
* gup_pmd_range() -> gup_fast_pmd_range()
* gup_pte_range() -> gup_fast_pte_range()
* gup_huge_pgd()  -> gup_fast_pgd_leaf()
* gup_huge_pud()  -> gup_fast_pud_leaf()
* gup_huge_pmd()  -> gup_fast_pmd_leaf()

The weird hugepd stuff:
* gup_huge_pd() -> gup_fast_hugepd()
* gup_hugepte() -> gup_fast_hugepte()

The weird devmap stuff:
* __gup_device_huge_pud() -> gup_fast_devmap_pud_leaf()
* __gup_device_huge_pmd   -> gup_fast_devmap_pmd_leaf()
* __gup_device_huge()     -> gup_fast_devmap_leaf()

Helper functions:
* unpin_user_pages_lockless() -> gup_fast_unpin_user_pages()
* gup_fast_folio_allowed() is already properly named
* gup_fast_permitted() is already properly named

With "gup_fast()", we now even have a function that is referred to in
comment in mm/mmu_gather.c.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/gup.c | 164 ++++++++++++++++++++++++++++---------------------------
 1 file changed, 84 insertions(+), 80 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 03b74b148e30..c293aff30c5d 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -440,7 +440,7 @@ void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages,
 }
 EXPORT_SYMBOL(unpin_user_page_range_dirty_lock);
 
-static void unpin_user_pages_lockless(struct page **pages, unsigned long npages)
+static void gup_fast_unpin_user_pages(struct page **pages, unsigned long npages)
 {
 	unsigned long i;
 	struct folio *folio;
@@ -2431,7 +2431,7 @@ long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
 EXPORT_SYMBOL(get_user_pages_unlocked);
 
 /*
- * Fast GUP
+ * GUP-fast
  *
  * get_user_pages_fast attempts to pin user pages by walking the page
  * tables directly and avoids taking locks. Thus the walker needs to be
@@ -2445,7 +2445,7 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
  *
  * Another way to achieve this is to batch up page table containing pages
  * belonging to more than one mm_user, then rcu_sched a callback to free those
- * pages. Disabling interrupts will allow the fast_gup walker to both block
+ * pages. Disabling interrupts will allow the gup_fast() walker to both block
  * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
  * (which is a relatively rare event). The code below adopts this strategy.
  *
@@ -2589,9 +2589,9 @@ static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start,
  * 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_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
-			 unsigned long end, unsigned int flags,
-			 struct page **pages, int *nr)
+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)
 {
 	struct dev_pagemap *pgmap = NULL;
 	int nr_start = *nr, ret = 0;
@@ -2688,20 +2688,19 @@ static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
  *
  * For a futex to be placed on a THP tail page, get_futex_key requires a
  * get_user_pages_fast_only implementation that can pin pages. Thus it's still
- * useful to have gup_huge_pmd even if we can't operate on ptes.
+ * useful to have gup_fast_pmd_leaf even if we can't operate on ptes.
  */
-static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
-			 unsigned long end, unsigned int flags,
-			 struct page **pages, int *nr)
+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)
 {
 	return 0;
 }
 #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 
 #if defined(CONFIG_ARCH_HAS_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
-static int __gup_device_huge(unsigned long pfn, unsigned long addr,
-			     unsigned long end, unsigned int flags,
-			     struct page **pages, int *nr)
+static int gup_fast_devmap_leaf(unsigned long pfn, unsigned long addr,
+	unsigned long end, unsigned int flags, struct page **pages, int *nr)
 {
 	int nr_start = *nr;
 	struct dev_pagemap *pgmap = NULL;
@@ -2734,15 +2733,15 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
 	return addr == end;
 }
 
-static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
-				 unsigned long end, unsigned int flags,
-				 struct page **pages, int *nr)
+static int gup_fast_devmap_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
+		unsigned long end, unsigned int flags, struct page **pages,
+		int *nr)
 {
 	unsigned long fault_pfn;
 	int nr_start = *nr;
 
 	fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
-	if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
+	if (!gup_fast_devmap_leaf(fault_pfn, addr, end, flags, pages, nr))
 		return 0;
 
 	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
@@ -2752,15 +2751,15 @@ static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
 	return 1;
 }
 
-static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
-				 unsigned long end, unsigned int flags,
-				 struct page **pages, int *nr)
+static int gup_fast_devmap_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
+		unsigned long end, unsigned int flags, struct page **pages,
+		int *nr)
 {
 	unsigned long fault_pfn;
 	int nr_start = *nr;
 
 	fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
-	if (!__gup_device_huge(fault_pfn, addr, end, flags, pages, nr))
+	if (!gup_fast_devmap_leaf(fault_pfn, addr, end, flags, pages, nr))
 		return 0;
 
 	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
@@ -2770,17 +2769,17 @@ static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
 	return 1;
 }
 #else
-static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
-				 unsigned long end, unsigned int flags,
-				 struct page **pages, int *nr)
+static int gup_fast_devmap_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
+		unsigned long end, unsigned int flags, struct page **pages,
+		int *nr)
 {
 	BUILD_BUG();
 	return 0;
 }
 
-static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr,
-				 unsigned long end, unsigned int flags,
-				 struct page **pages, int *nr)
+static int gup_fast_devmap_pud_leaf(pud_t pud, pud_t *pudp, unsigned long addr,
+		unsigned long end, unsigned int flags, struct page **pages,
+		int *nr)
 {
 	BUILD_BUG();
 	return 0;
@@ -2806,9 +2805,9 @@ static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
 	return (__boundary - 1 < end - 1) ? __boundary : end;
 }
 
-static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
-		       unsigned long end, unsigned int flags,
-		       struct page **pages, int *nr)
+static int gup_fast_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
+		unsigned long end, unsigned int flags, struct page **pages,
+		int *nr)
 {
 	unsigned long pte_end;
 	struct page *page;
@@ -2855,7 +2854,7 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 	return 1;
 }
 
-static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
+static int gup_fast_hugepd(hugepd_t hugepd, unsigned long addr,
 		unsigned int pdshift, unsigned long end, unsigned int flags,
 		struct page **pages, int *nr)
 {
@@ -2866,14 +2865,14 @@ static int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
 	ptep = hugepte_offset(hugepd, addr, pdshift);
 	do {
 		next = hugepte_addr_end(addr, end, sz);
-		if (!gup_hugepte(ptep, sz, addr, end, flags, pages, nr))
+		if (!gup_fast_hugepte(ptep, sz, addr, end, flags, pages, nr))
 			return 0;
 	} while (ptep++, addr = next, addr != end);
 
 	return 1;
 }
 #else
-static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
+static inline int gup_fast_hugepd(hugepd_t hugepd, unsigned long addr,
 		unsigned int pdshift, unsigned long end, unsigned int flags,
 		struct page **pages, int *nr)
 {
@@ -2881,9 +2880,9 @@ static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr,
 }
 #endif /* CONFIG_ARCH_HAS_HUGEPD */
 
-static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
-			unsigned long end, unsigned int flags,
-			struct page **pages, int *nr)
+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)
 {
 	struct page *page;
 	struct folio *folio;
@@ -2895,8 +2894,8 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
 	if (pmd_devmap(orig)) {
 		if (unlikely(flags & FOLL_LONGTERM))
 			return 0;
-		return __gup_device_huge_pmd(orig, pmdp, addr, end, flags,
-					     pages, nr);
+		return gup_fast_devmap_pmd_leaf(orig, pmdp, addr, end, flags,
+					        pages, nr);
 	}
 
 	page = nth_page(pmd_page(orig), (addr & ~PMD_MASK) >> PAGE_SHIFT);
@@ -2925,9 +2924,9 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
 	return 1;
 }
 
-static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
-			unsigned long end, unsigned int flags,
-			struct page **pages, int *nr)
+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)
 {
 	struct page *page;
 	struct folio *folio;
@@ -2939,8 +2938,8 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
 	if (pud_devmap(orig)) {
 		if (unlikely(flags & FOLL_LONGTERM))
 			return 0;
-		return __gup_device_huge_pud(orig, pudp, addr, end, flags,
-					     pages, nr);
+		return gup_fast_devmap_pud_leaf(orig, pudp, addr, end, flags,
+					        pages, nr);
 	}
 
 	page = nth_page(pud_page(orig), (addr & ~PUD_MASK) >> PAGE_SHIFT);
@@ -2970,9 +2969,9 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
 	return 1;
 }
 
-static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
-			unsigned long end, unsigned int flags,
-			struct page **pages, int *nr)
+static int gup_fast_pgd_leaf(pgd_t orig, pgd_t *pgdp, unsigned long addr,
+		unsigned long end, unsigned int flags, struct page **pages,
+		int *nr)
 {
 	int refs;
 	struct page *page;
@@ -3010,8 +3009,9 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
 	return 1;
 }
 
-static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned long end,
-		unsigned int flags, struct page **pages, int *nr)
+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)
 {
 	unsigned long next;
 	pmd_t *pmdp;
@@ -3025,11 +3025,11 @@ static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned lo
 			return 0;
 
 		if (unlikely(pmd_leaf(pmd))) {
-			/* See gup_pte_range() */
+			/* See gup_fast_pte_range() */
 			if (pmd_protnone(pmd))
 				return 0;
 
-			if (!gup_huge_pmd(pmd, pmdp, addr, next, flags,
+			if (!gup_fast_pmd_leaf(pmd, pmdp, addr, next, flags,
 				pages, nr))
 				return 0;
 
@@ -3038,18 +3038,20 @@ static int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, unsigned lo
 			 * architecture have different format for hugetlbfs
 			 * pmd format and THP pmd format
 			 */
-			if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr,
-					 PMD_SHIFT, next, flags, pages, nr))
+			if (!gup_fast_hugepd(__hugepd(pmd_val(pmd)), addr,
+					     PMD_SHIFT, next, flags, pages, nr))
 				return 0;
-		} else if (!gup_pte_range(pmd, pmdp, addr, next, flags, pages, nr))
+		} else if (!gup_fast_pte_range(pmd, pmdp, addr, next, flags,
+					       pages, nr))
 			return 0;
 	} while (pmdp++, addr = next, addr != end);
 
 	return 1;
 }
 
-static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned long end,
-			 unsigned int flags, struct page **pages, int *nr)
+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)
 {
 	unsigned long next;
 	pud_t *pudp;
@@ -3062,22 +3064,24 @@ static int gup_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, unsigned lo
 		if (unlikely(!pud_present(pud)))
 			return 0;
 		if (unlikely(pud_leaf(pud))) {
-			if (!gup_huge_pud(pud, pudp, addr, next, flags,
-					  pages, nr))
+			if (!gup_fast_pud_leaf(pud, pudp, addr, next, flags,
+					       pages, nr))
 				return 0;
 		} else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) {
-			if (!gup_huge_pd(__hugepd(pud_val(pud)), addr,
-					 PUD_SHIFT, next, flags, pages, nr))
+			if (!gup_fast_hugepd(__hugepd(pud_val(pud)), addr,
+					     PUD_SHIFT, next, flags, pages, nr))
 				return 0;
-		} else if (!gup_pmd_range(pudp, pud, addr, next, flags, pages, nr))
+		} else if (!gup_fast_pmd_range(pudp, pud, addr, next, flags,
+					       pages, nr))
 			return 0;
 	} while (pudp++, addr = next, addr != end);
 
 	return 1;
 }
 
-static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned long end,
-			 unsigned int flags, struct page **pages, int *nr)
+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)
 {
 	unsigned long next;
 	p4d_t *p4dp;
@@ -3091,17 +3095,18 @@ static int gup_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, unsigned lo
 			return 0;
 		BUILD_BUG_ON(p4d_leaf(p4d));
 		if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) {
-			if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr,
-					 P4D_SHIFT, next, flags, pages, nr))
+			if (!gup_fast_hugepd(__hugepd(p4d_val(p4d)), addr,
+					     P4D_SHIFT, next, flags, pages, nr))
 				return 0;
-		} else if (!gup_pud_range(p4dp, p4d, addr, next, flags, pages, nr))
+		} else if (!gup_fast_pud_range(p4dp, p4d, addr, next, flags,
+					       pages, nr))
 			return 0;
 	} while (p4dp++, addr = next, addr != end);
 
 	return 1;
 }
 
-static void gup_pgd_range(unsigned long addr, unsigned long end,
+static void gup_fast_pgd_range(unsigned long addr, unsigned long end,
 		unsigned int flags, struct page **pages, int *nr)
 {
 	unsigned long next;
@@ -3115,19 +3120,20 @@ static void gup_pgd_range(unsigned long addr, unsigned long end,
 		if (pgd_none(pgd))
 			return;
 		if (unlikely(pgd_leaf(pgd))) {
-			if (!gup_huge_pgd(pgd, pgdp, addr, next, flags,
-					  pages, nr))
+			if (!gup_fast_pgd_leaf(pgd, pgdp, addr, next, flags,
+					       pages, nr))
 				return;
 		} else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) {
-			if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr,
-					 PGDIR_SHIFT, next, flags, pages, nr))
+			if (!gup_fast_hugepd(__hugepd(pgd_val(pgd)), addr,
+					      PGDIR_SHIFT, next, flags, pages, nr))
 				return;
-		} else if (!gup_p4d_range(pgdp, pgd, addr, next, flags, pages, nr))
+		} else if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags,
+					       pages, nr))
 			return;
 	} while (pgdp++, addr = next, addr != end);
 }
 #else
-static inline void gup_pgd_range(unsigned long addr, unsigned long end,
+static inline void gup_fast_pgd_range(unsigned long addr, unsigned long end,
 		unsigned int flags, struct page **pages, int *nr)
 {
 }
@@ -3144,10 +3150,8 @@ static bool gup_fast_permitted(unsigned long start, unsigned long end)
 }
 #endif
 
-static unsigned long lockless_pages_from_mm(unsigned long start,
-					    unsigned long end,
-					    unsigned int gup_flags,
-					    struct page **pages)
+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;
@@ -3175,16 +3179,16 @@ static unsigned long lockless_pages_from_mm(unsigned long start,
 	 * that come from THPs splitting.
 	 */
 	local_irq_save(flags);
-	gup_pgd_range(start, end, gup_flags, pages, &nr_pinned);
+	gup_fast_pgd_range(start, end, gup_flags, pages, &nr_pinned);
 	local_irq_restore(flags);
 
 	/*
 	 * When pinning pages for DMA there could be a concurrent write protect
-	 * from fork() via copy_page_range(), in this case always fail fast GUP.
+	 * from fork() via copy_page_range(), in this case always fail GUP-fast.
 	 */
 	if (gup_flags & FOLL_PIN) {
 		if (read_seqcount_retry(&current->mm->write_protect_seq, seq)) {
-			unpin_user_pages_lockless(pages, nr_pinned);
+			gup_fast_unpin_user_pages(pages, nr_pinned);
 			return 0;
 		} else {
 			sanity_check_pinned_pages(pages, nr_pinned);
@@ -3224,7 +3228,7 @@ static int internal_get_user_pages_fast(unsigned long start,
 	if (unlikely(!access_ok((void __user *)start, len)))
 		return -EFAULT;
 
-	nr_pinned = lockless_pages_from_mm(start, end, gup_flags, pages);
+	nr_pinned = gup_fast(start, end, gup_flags, pages);
 	if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY)
 		return nr_pinned;
 
-- 
2.43.2