Message-ID: <20210616105937.23201-2-apopple@nvidia.com>
Date:   Wed, 16 Jun 2021 20:59:28 +1000
From:   Alistair Popple <apopple@...dia.com>
To:     <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <rcampbell@...dia.com>,
        <willy@...radead.org>, <linux-doc@...r.kernel.org>,
        <nouveau@...ts.freedesktop.org>, <hughd@...gle.com>,
        <linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <hch@...radead.org>, <peterx@...hat.com>, <shakeelb@...gle.com>,
        <bskeggs@...hat.com>, <jgg@...dia.com>, <jhubbard@...dia.com>,
        Alistair Popple <apopple@...dia.com>,
        "Christoph Hellwig" <hch@....de>
Subject: [PATCH v11 01/10] mm: Remove special swap entry functions

Remove multiple similar inline functions for dealing with different
types of special swap entries.

Both migration and device private swap entries use the swap offset to
store a pfn. Instead of multiple inline functions to obtain a struct
page for each swap entry type use a common function
pfn_swap_entry_to_page(). Also open-code the various entry_to_pfn()
functions as this results is shorter code that is easier to understand.

Signed-off-by: Alistair Popple <apopple@...dia.com>
Reviewed-by: Ralph Campbell <rcampbell@...dia.com>
Reviewed-by: Christoph Hellwig <hch@....de>

---

v11:
* Rebased on mmotm

v9:
* Rebased on v5.13-rc2

v8:
* No changes

v7:
* Reworded commit message to include pfn_swap_entry_to_page()
* Added Christoph's Reviewed-by

v6:
* Removed redundant compound_page() call from inside PageLocked()
* Fixed a minor build issue for s390 reported by kernel test bot

v4:
* Added pfn_swap_entry_to_page()
* Reinstated check that migration entries point to locked pages
* Removed #define swapcache_prepare which isn't needed for CONFIG_SWAP=0
  builds
---
 arch/s390/mm/pgtable.c  |  2 +-
 fs/proc/task_mmu.c      | 23 +++++---------
 include/linux/swap.h    |  4 +--
 include/linux/swapops.h | 69 ++++++++++++++---------------------------
 mm/hmm.c                |  5 ++-
 mm/huge_memory.c        |  6 ++--
 mm/memcontrol.c         |  2 +-
 mm/memory.c             | 10 +++---
 mm/migrate.c            |  6 ++--
 mm/page_vma_mapped.c    |  6 ++--
 10 files changed, 51 insertions(+), 82 deletions(-)

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 18205f851c24..eec3a9d7176e 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -691,7 +691,7 @@ static void ptep_zap_swap_entry(struct mm_struct *mm, swp_entry_t entry)
 	if (!non_swap_entry(entry))
 		dec_mm_counter(mm, MM_SWAPENTS);
 	else if (is_migration_entry(entry)) {
-		struct page *page = migration_entry_to_page(entry);
+		struct page *page = pfn_swap_entry_to_page(entry);
 
 		dec_mm_counter(mm, mm_counter(page));
 	}
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 95c8f1e8fea6..eb97468dfe4c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -514,10 +514,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
 			} else {
 				mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT;
 			}
-		} else if (is_migration_entry(swpent))
-			page = migration_entry_to_page(swpent);
-		else if (is_device_private_entry(swpent))
-			page = device_private_entry_to_page(swpent);
+		} else if (is_pfn_swap_entry(swpent))
+			page = pfn_swap_entry_to_page(swpent);
 	} else if (unlikely(IS_ENABLED(CONFIG_SHMEM) && mss->check_shmem_swap
 							&& pte_none(*pte))) {
 		page = xa_load(&vma->vm_file->f_mapping->i_pages,
@@ -549,7 +547,7 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
 		swp_entry_t entry = pmd_to_swp_entry(*pmd);
 
 		if (is_migration_entry(entry))
-			page = migration_entry_to_page(entry);
+			page = pfn_swap_entry_to_page(entry);
 	}
 	if (IS_ERR_OR_NULL(page))
 		return;
@@ -694,10 +692,8 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
 	} else if (is_swap_pte(*pte)) {
 		swp_entry_t swpent = pte_to_swp_entry(*pte);
 
-		if (is_migration_entry(swpent))
-			page = migration_entry_to_page(swpent);
-		else if (is_device_private_entry(swpent))
-			page = device_private_entry_to_page(swpent);
+		if (is_pfn_swap_entry(swpent))
+			page = pfn_swap_entry_to_page(swpent);
 	}
 	if (page) {
 		int mapcount = page_mapcount(page);
@@ -1389,11 +1385,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
 			frame = swp_type(entry) |
 				(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
 		flags |= PM_SWAP;
-		if (is_migration_entry(entry))
-			page = migration_entry_to_page(entry);
-
-		if (is_device_private_entry(entry))
-			page = device_private_entry_to_page(entry);
+		if (is_pfn_swap_entry(entry))
+			page = pfn_swap_entry_to_page(entry);
 	}
 
 	if (page && !PageAnon(page))
@@ -1454,7 +1447,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
 			if (pmd_swp_uffd_wp(pmd))
 				flags |= PM_UFFD_WP;
 			VM_BUG_ON(!is_pmd_migration_entry(pmd));
-			page = migration_entry_to_page(entry);
+			page = pfn_swap_entry_to_page(entry);
 		}
 #endif
 
diff --git a/include/linux/swap.h b/include/linux/swap.h
index ac9bd84c905e..df7cbb6b3d3e 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -564,8 +564,8 @@ static inline void show_swap_cache_info(void)
 {
 }
 
-#define free_swap_and_cache(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
-#define swapcache_prepare(e) ({(is_migration_entry(e) || is_device_private_entry(e));})
+/* used to sanity check ptes in zap_pte_range when CONFIG_SWAP=0 */
+#define free_swap_and_cache(e) is_pfn_swap_entry(e)
 
 static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
 {
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 708fbeb21dd3..c24c79812bc1 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -128,16 +128,6 @@ static inline bool is_write_device_private_entry(swp_entry_t entry)
 {
 	return unlikely(swp_type(entry) == SWP_DEVICE_WRITE);
 }
-
-static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry)
-{
-	return swp_offset(entry);
-}
-
-static inline struct page *device_private_entry_to_page(swp_entry_t entry)
-{
-	return pfn_to_page(swp_offset(entry));
-}
 #else /* CONFIG_DEVICE_PRIVATE */
 static inline swp_entry_t make_device_private_entry(struct page *page, bool write)
 {
@@ -157,16 +147,6 @@ static inline bool is_write_device_private_entry(swp_entry_t entry)
 {
 	return false;
 }
-
-static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry)
-{
-	return 0;
-}
-
-static inline struct page *device_private_entry_to_page(swp_entry_t entry)
-{
-	return NULL;
-}
 #endif /* CONFIG_DEVICE_PRIVATE */
 
 #ifdef CONFIG_MIGRATION
@@ -189,22 +169,6 @@ static inline int is_write_migration_entry(swp_entry_t entry)
 	return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
 }
 
-static inline unsigned long migration_entry_to_pfn(swp_entry_t entry)
-{
-	return swp_offset(entry);
-}
-
-static inline struct page *migration_entry_to_page(swp_entry_t entry)
-{
-	struct page *p = pfn_to_page(swp_offset(entry));
-	/*
-	 * Any use of migration entries may only occur while the
-	 * corresponding page is locked
-	 */
-	BUG_ON(!PageLocked(compound_head(p)));
-	return p;
-}
-
 static inline void make_migration_entry_read(swp_entry_t *entry)
 {
 	*entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
@@ -224,16 +188,6 @@ static inline int is_migration_entry(swp_entry_t swp)
 	return 0;
 }
 
-static inline unsigned long migration_entry_to_pfn(swp_entry_t entry)
-{
-	return 0;
-}
-
-static inline struct page *migration_entry_to_page(swp_entry_t entry)
-{
-	return NULL;
-}
-
 static inline void make_migration_entry_read(swp_entry_t *entryp) { }
 static inline void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
 					spinlock_t *ptl) { }
@@ -248,6 +202,29 @@ static inline int is_write_migration_entry(swp_entry_t entry)
 
 #endif
 
+static inline struct page *pfn_swap_entry_to_page(swp_entry_t entry)
+{
+	struct page *p = pfn_to_page(swp_offset(entry));
+
+	/*
+	 * Any use of migration entries may only occur while the
+	 * corresponding page is locked
+	 */
+	BUG_ON(is_migration_entry(entry) && !PageLocked(p));
+
+	return p;
+}
+
+/*
+ * A pfn swap entry is a special type of swap entry that always has a pfn stored
+ * in the swap offset. They are used to represent unaddressable device memory
+ * and to restrict access to a page undergoing migration.
+ */
+static inline bool is_pfn_swap_entry(swp_entry_t entry)
+{
+	return is_migration_entry(entry) || is_device_private_entry(entry);
+}
+
 struct page_vma_mapped_walk;
 
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
diff --git a/mm/hmm.c b/mm/hmm.c
index 943cb2ba4442..3b2dda71d0ed 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -214,7 +214,7 @@ static inline bool hmm_is_device_private_entry(struct hmm_range *range,
 		swp_entry_t entry)
 {
 	return is_device_private_entry(entry) &&
-		device_private_entry_to_page(entry)->pgmap->owner ==
+		pfn_swap_entry_to_page(entry)->pgmap->owner ==
 		range->dev_private_owner;
 }
 
@@ -257,8 +257,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 			cpu_flags = HMM_PFN_VALID;
 			if (is_write_device_private_entry(entry))
 				cpu_flags |= HMM_PFN_WRITE;
-			*hmm_pfn = device_private_entry_to_pfn(entry) |
-					cpu_flags;
+			*hmm_pfn = swp_offset(entry) | cpu_flags;
 			return 0;
 		}
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d513b0cd1161..327b8d9d8d2f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1643,7 +1643,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 
 			VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
 			entry = pmd_to_swp_entry(orig_pmd);
-			page = migration_entry_to_page(entry);
+			page = pfn_swap_entry_to_page(entry);
 			flush_needed = 0;
 		} else
 			WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
@@ -2012,7 +2012,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 			swp_entry_t entry;
 
 			entry = pmd_to_swp_entry(old_pmd);
-			page = migration_entry_to_page(entry);
+			page = pfn_swap_entry_to_page(entry);
 		} else {
 			page = pmd_page(old_pmd);
 			if (!PageDirty(page) && pmd_dirty(old_pmd))
@@ -2066,7 +2066,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 		swp_entry_t entry;
 
 		entry = pmd_to_swp_entry(old_pmd);
-		page = migration_entry_to_page(entry);
+		page = pfn_swap_entry_to_page(entry);
 		write = is_write_migration_entry(entry);
 		young = false;
 		soft_dirty = pmd_swp_soft_dirty(old_pmd);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dce5154fbb8f..ae1f5d0cb581 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5537,7 +5537,7 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
 	 * as special swap entry in the CPU page table.
 	 */
 	if (is_device_private_entry(ent)) {
-		page = device_private_entry_to_page(ent);
+		page = pfn_swap_entry_to_page(ent);
 		/*
 		 * MEMORY_DEVICE_PRIVATE means ZONE_DEVICE page and which have
 		 * a refcount of 1 when free (unlike normal page)
diff --git a/mm/memory.c b/mm/memory.c
index a5af7d854776..a6c5132354a2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -729,7 +729,7 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		}
 		rss[MM_SWAPENTS]++;
 	} else if (is_migration_entry(entry)) {
-		page = migration_entry_to_page(entry);
+		page = pfn_swap_entry_to_page(entry);
 
 		rss[mm_counter(page)]++;
 
@@ -748,7 +748,7 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 			set_pte_at(src_mm, addr, src_pte, pte);
 		}
 	} else if (is_device_private_entry(entry)) {
-		page = device_private_entry_to_page(entry);
+		page = pfn_swap_entry_to_page(entry);
 
 		/*
 		 * Update rss count even for unaddressable pages, as
@@ -1280,7 +1280,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 
 		entry = pte_to_swp_entry(ptent);
 		if (is_device_private_entry(entry)) {
-			struct page *page = device_private_entry_to_page(entry);
+			struct page *page = pfn_swap_entry_to_page(entry);
 
 			if (unlikely(details && details->check_mapping)) {
 				/*
@@ -1309,7 +1309,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 		else if (is_migration_entry(entry)) {
 			struct page *page;
 
-			page = migration_entry_to_page(entry);
+			page = pfn_swap_entry_to_page(entry);
 			rss[mm_counter(page)]--;
 		}
 		if (unlikely(!free_swap_and_cache(entry)))
@@ -3372,7 +3372,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			migration_entry_wait(vma->vm_mm, vmf->pmd,
 					     vmf->address);
 		} else if (is_device_private_entry(entry)) {
-			vmf->page = device_private_entry_to_page(entry);
+			vmf->page = pfn_swap_entry_to_page(entry);
 			ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
 		} else if (is_hwpoison_entry(entry)) {
 			ret = VM_FAULT_HWPOISON;
diff --git a/mm/migrate.c b/mm/migrate.c
index 8810c1421f5d..b4abb87249e1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -296,7 +296,7 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
 	if (!is_migration_entry(entry))
 		goto out;
 
-	page = migration_entry_to_page(entry);
+	page = pfn_swap_entry_to_page(entry);
 	page = compound_head(page);
 
 	/*
@@ -337,7 +337,7 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
 	ptl = pmd_lock(mm, pmd);
 	if (!is_pmd_migration_entry(*pmd))
 		goto unlock;
-	page = migration_entry_to_page(pmd_to_swp_entry(*pmd));
+	page = pfn_swap_entry_to_page(pmd_to_swp_entry(*pmd));
 	if (!get_page_unless_zero(page))
 		goto unlock;
 	spin_unlock(ptl);
@@ -2289,7 +2289,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 			if (!is_device_private_entry(entry))
 				goto next;
 
-			page = device_private_entry_to_page(entry);
+			page = pfn_swap_entry_to_page(entry);
 			if (!(migrate->flags &
 				MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
 			    page->pgmap->owner != migrate->pgmap_owner)
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 3dd350a941aa..082e8073af56 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -96,7 +96,7 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw)
 		if (!is_migration_entry(entry))
 			return false;
 
-		pfn = migration_entry_to_pfn(entry);
+		pfn = swp_offset(entry);
 	} else if (is_swap_pte(*pvmw->pte)) {
 		swp_entry_t entry;
 
@@ -105,7 +105,7 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw)
 		if (!is_device_private_entry(entry))
 			return false;
 
-		pfn = device_private_entry_to_pfn(entry);
+		pfn = swp_offset(entry);
 	} else {
 		if (!pte_present(*pvmw->pte))
 			return false;
@@ -233,7 +233,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 					return not_found(pvmw);
 				entry = pmd_to_swp_entry(pmde);
 				if (!is_migration_entry(entry) ||
-				    migration_entry_to_page(entry) != page)
+				    pfn_swap_entry_to_page(entry) != page)
 					return not_found(pvmw);
 				return true;
 			}
-- 
2.20.1

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