[PATCH v3 2/8] mm/swapops: Rework swap entry manipulation code

From: Alistair Popple
Date: Fri Feb 26 2021 - 02:20:10 EST

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In reply to: Christoph Hellwig: "Re: [PATCH v3 1/8] mm: Remove special swap entry functions"
Next in thread: Christoph Hellwig: "Re: [PATCH v3 2/8] mm/swapops: Rework swap entry manipulation code"
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Both migration and device private pages use special swap entries which
are manipluated by a range of inline functions. The arguments to these
are somewhat inconsitent so rework them to remove flag type arguments
and to make the arguments similar for both a read and write entry
creation.

Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
---
include/linux/swapops.h | 56 ++++++++++++++++++++++-------------------
mm/debug_vm_pgtable.c | 12 ++++-----
mm/hmm.c | 2 +-
mm/huge_memory.c | 26 +++++++++++++------
mm/hugetlb.c | 10 +++++---
mm/memory.c | 10 +++++---
mm/migrate.c | 26 ++++++++++++++-----
mm/mprotect.c | 10 +++++---
mm/rmap.c | 10 +++++---
9 files changed, 100 insertions(+), 62 deletions(-)

diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 80cfa3985045..256b9683b262 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -100,35 +100,35 @@ static inline void *swp_to_radix_entry(swp_entry_t entry)
}

#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
-static inline swp_entry_t make_device_private_entry(struct page *page, bool write)
+static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
{
- return swp_entry(write ? SWP_DEVICE_WRITE : SWP_DEVICE_READ,
- page_to_pfn(page));
+ return swp_entry(SWP_DEVICE_READ, offset);
}

-static inline bool is_device_private_entry(swp_entry_t entry)
+static inline swp_entry_t make_writable_device_private_entry(pgoff_t offset)
{
- int type = swp_type(entry);
- return type == SWP_DEVICE_READ || type == SWP_DEVICE_WRITE;
+ return swp_entry(SWP_DEVICE_WRITE, offset);
}

-static inline void make_device_private_entry_read(swp_entry_t *entry)
+static inline bool is_device_private_entry(swp_entry_t entry)
{
- *entry = swp_entry(SWP_DEVICE_READ, swp_offset(*entry));
+ int type = swp_type(entry);
+ return type == SWP_DEVICE_READ || type == SWP_DEVICE_WRITE;
}

-static inline bool is_write_device_private_entry(swp_entry_t entry)
+static inline bool is_writable_device_private_entry(swp_entry_t entry)
{
return unlikely(swp_type(entry) == SWP_DEVICE_WRITE);
}
#else /* CONFIG_DEVICE_PRIVATE */
-static inline swp_entry_t make_device_private_entry(struct page *page, bool write)
+static inline swp_entry_t make_readable_device_private_entry(pgoff_t offset)
{
return swp_entry(0, 0);
}

-static inline void make_device_private_entry_read(swp_entry_t *entry)
+static inline swp_entry_t make_writable_device_private_entry(pgoff_t offset)
{
+ return swp_entry(0, 0);
}

static inline bool is_device_private_entry(swp_entry_t entry)
@@ -136,35 +136,32 @@ static inline bool is_device_private_entry(swp_entry_t entry)
return false;
}

-static inline bool is_write_device_private_entry(swp_entry_t entry)
+static inline bool is_writable_device_private_entry(swp_entry_t entry)
{
return false;
}
#endif /* CONFIG_DEVICE_PRIVATE */

#ifdef CONFIG_MIGRATION
-static inline swp_entry_t make_migration_entry(struct page *page, int write)
-{
- BUG_ON(!PageLocked(compound_head(page)));
-
- return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
- page_to_pfn(page));
-}
-
static inline int is_migration_entry(swp_entry_t entry)
{
return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
swp_type(entry) == SWP_MIGRATION_WRITE);
}

-static inline int is_write_migration_entry(swp_entry_t entry)
+static inline int is_writable_migration_entry(swp_entry_t entry)
{
return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
}

-static inline void make_migration_entry_read(swp_entry_t *entry)
+static inline swp_entry_t make_readable_migration_entry(pgoff_t offset)
{
- *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
+ return swp_entry(SWP_MIGRATION_READ, offset);
+}
+
+static inline swp_entry_t make_writable_migration_entry(pgoff_t offset)
+{
+ return swp_entry(SWP_MIGRATION_WRITE, offset);
}

extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
@@ -174,21 +171,28 @@ extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
extern void migration_entry_wait_huge(struct vm_area_struct *vma,
struct mm_struct *mm, pte_t *pte);
#else
+static inline swp_entry_t make_readable_migration_entry(pgoff_t offset)
+{
+ return swp_entry(0, 0);
+}
+
+static inline swp_entry_t make_writable_migration_entry(pgoff_t offset)
+{
+ return swp_entry(0, 0);
+}

-#define make_migration_entry(page, write) swp_entry(0, 0)
static inline int is_migration_entry(swp_entry_t swp)
{
return 0;
}

-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) { }
static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address) { }
static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
struct mm_struct *mm, pte_t *pte) { }
-static inline int is_write_migration_entry(swp_entry_t entry)
+static inline int is_writable_migration_entry(swp_entry_t entry)
{
return 0;
}
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index c05d9dcf7891..4932f65a88d4 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -772,17 +772,17 @@ static void __init swap_migration_tests(void)
* locked, otherwise it stumbles upon a BUG_ON().
*/
__SetPageLocked(page);
- swp = make_migration_entry(page, 1);
+ swp = make_writable_migration_entry(page_to_pfn(page));
WARN_ON(!is_migration_entry(swp));
- WARN_ON(!is_write_migration_entry(swp));
+ WARN_ON(!is_writable_migration_entry(swp));

- make_migration_entry_read(&swp);
+ swp = make_readable_migration_entry(swp_offset(swp));
WARN_ON(!is_migration_entry(swp));
- WARN_ON(is_write_migration_entry(swp));
+ WARN_ON(is_writable_migration_entry(swp));

- swp = make_migration_entry(page, 0);
+ swp = make_readable_migration_entry(page_to_pfn(page));
WARN_ON(!is_migration_entry(swp));
- WARN_ON(is_write_migration_entry(swp));
+ WARN_ON(is_writable_migration_entry(swp));
__ClearPageLocked(page);
__free_page(page);
}
diff --git a/mm/hmm.c b/mm/hmm.c
index b10494b18b65..a1f9f268893d 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -255,7 +255,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
*/
if (hmm_is_device_private_entry(range, entry)) {
cpu_flags = HMM_PFN_VALID;
- if (is_write_device_private_entry(entry))
+ if (is_writable_device_private_entry(entry))
cpu_flags |= HMM_PFN_WRITE;
*hmm_pfn = swp_offset(entry) | cpu_flags;
return 0;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 91ca9b103ee5..d00b93dc2d9e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1046,8 +1046,9 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
swp_entry_t entry = pmd_to_swp_entry(pmd);

VM_BUG_ON(!is_pmd_migration_entry(pmd));
- if (is_write_migration_entry(entry)) {
- make_migration_entry_read(&entry);
+ if (is_writable_migration_entry(entry)) {
+ entry = make_readable_migration_entry(
+ swp_offset(entry));
pmd = swp_entry_to_pmd(entry);
if (pmd_swp_soft_dirty(*src_pmd))
pmd = pmd_swp_mksoft_dirty(pmd);
@@ -1820,13 +1821,14 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
swp_entry_t entry = pmd_to_swp_entry(*pmd);

VM_BUG_ON(!is_pmd_migration_entry(*pmd));
- if (is_write_migration_entry(entry)) {
+ if (is_writable_migration_entry(entry)) {
pmd_t newpmd;
/*
* A protection check is difficult so
* just be safe and disable write
*/
- make_migration_entry_read(&entry);
+ entry = make_readable_migration_entry(
+ swp_offset(entry));
newpmd = swp_entry_to_pmd(entry);
if (pmd_swp_soft_dirty(*pmd))
newpmd = pmd_swp_mksoft_dirty(newpmd);
@@ -2104,7 +2106,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,

entry = pmd_to_swp_entry(old_pmd);
page = pfn_to_page(swp_offset(entry));
- write = is_write_migration_entry(entry);
+ write = is_writable_migration_entry(entry);
young = false;
soft_dirty = pmd_swp_soft_dirty(old_pmd);
uffd_wp = pmd_swp_uffd_wp(old_pmd);
@@ -2136,7 +2138,12 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
*/
if (freeze || pmd_migration) {
swp_entry_t swp_entry;
- swp_entry = make_migration_entry(page + i, write);
+ if (write)
+ swp_entry = make_writable_migration_entry(
+ page_to_pfn(page + i));
+ else
+ swp_entry = make_readable_migration_entry(
+ page_to_pfn(page + i));
entry = swp_entry_to_pte(swp_entry);
if (soft_dirty)
entry = pte_swp_mksoft_dirty(entry);
@@ -2988,7 +2995,10 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
if (pmd_dirty(pmdval))
set_page_dirty(page);
- entry = make_migration_entry(page, pmd_write(pmdval));
+ if (pmd_write(pmdval))
+ entry = make_writable_migration_entry(page_to_pfn(page));
+ else
+ entry = make_readable_migration_entry(page_to_pfn(page));
pmdswp = swp_entry_to_pmd(entry);
if (pmd_soft_dirty(pmdval))
pmdswp = pmd_swp_mksoft_dirty(pmdswp);
@@ -3014,7 +3024,7 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
if (pmd_swp_soft_dirty(*pvmw->pmd))
pmde = pmd_mksoft_dirty(pmde);
- if (is_write_migration_entry(entry))
+ if (is_writable_migration_entry(entry))
pmde = maybe_pmd_mkwrite(pmde, vma);

flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4bdb58ab14cb..37cde6d4303c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3842,12 +3842,13 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
is_hugetlb_entry_hwpoisoned(entry))) {
swp_entry_t swp_entry = pte_to_swp_entry(entry);

- if (is_write_migration_entry(swp_entry) && cow) {
+ if (is_writable_migration_entry(swp_entry) && cow) {
/*
* COW mappings require pages in both
* parent and child to be set to read.
*/
- make_migration_entry_read(&swp_entry);
+ swp_entry = make_readable_migration_entry(
+ swp_offset(swp_entry));
entry = swp_entry_to_pte(swp_entry);
set_huge_swap_pte_at(src, addr, src_pte,
entry, sz);
@@ -5019,10 +5020,11 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
if (unlikely(is_hugetlb_entry_migration(pte))) {
swp_entry_t entry = pte_to_swp_entry(pte);

- if (is_write_migration_entry(entry)) {
+ if (is_writable_migration_entry(entry)) {
pte_t newpte;

- make_migration_entry_read(&entry);
+ entry = make_readable_migration_entry(
+ swp_offset(entry));
newpte = swp_entry_to_pte(entry);
set_huge_swap_pte_at(mm, address, ptep,
newpte, huge_page_size(h));
diff --git a/mm/memory.c b/mm/memory.c
index 817d7a11ab7e..4d17a92a938b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -722,13 +722,14 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,

rss[mm_counter(page)]++;

- if (is_write_migration_entry(entry) &&
+ if (is_writable_migration_entry(entry) &&
is_cow_mapping(vm_flags)) {
/*
* COW mappings require pages in both
* parent and child to be set to read.
*/
- make_migration_entry_read(&entry);
+ entry = make_readable_migration_entry(
+ swp_offset(entry));
pte = swp_entry_to_pte(entry);
if (pte_swp_soft_dirty(*src_pte))
pte = pte_swp_mksoft_dirty(pte);
@@ -759,9 +760,10 @@ copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
* when a device driver is involved (you cannot easily
* save and restore device driver state).
*/
- if (is_write_device_private_entry(entry) &&
+ if (is_writable_device_private_entry(entry) &&
is_cow_mapping(vm_flags)) {
- make_device_private_entry_read(&entry);
+ entry = make_readable_device_private_entry(
+ swp_offset(entry));
pte = swp_entry_to_pte(entry);
if (pte_swp_uffd_wp(*src_pte))
pte = pte_swp_mkuffd_wp(pte);
diff --git a/mm/migrate.c b/mm/migrate.c
index 72adcc3d8f5b..3033cc42892a 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -237,13 +237,18 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
* Recheck VMA as permissions can change since migration started
*/
entry = pte_to_swp_entry(*pvmw.pte);
- if (is_write_migration_entry(entry))
+ if (is_writable_migration_entry(entry))
pte = maybe_mkwrite(pte, vma);
else if (pte_swp_uffd_wp(*pvmw.pte))
pte = pte_mkuffd_wp(pte);

if (unlikely(is_device_private_page(new))) {
- entry = make_device_private_entry(new, pte_write(pte));
+ if (pte_write(pte))
+ entry = make_writable_device_private_entry(
+ page_to_pfn(new));
+ else
+ entry = make_readable_device_private_entry(
+ page_to_pfn(new));
pte = swp_entry_to_pte(entry);
if (pte_swp_soft_dirty(*pvmw.pte))
pte = pte_swp_mksoft_dirty(pte);
@@ -2445,7 +2450,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,

mpfn = migrate_pfn(page_to_pfn(page)) |
MIGRATE_PFN_MIGRATE;
- if (is_write_device_private_entry(entry))
+ if (is_writable_device_private_entry(entry))
mpfn |= MIGRATE_PFN_WRITE;
} else {
if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
@@ -2491,8 +2496,12 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
ptep_get_and_clear(mm, addr, ptep);

/* Setup special migration page table entry */
- entry = make_migration_entry(page, mpfn &
- MIGRATE_PFN_WRITE);
+ if (mpfn & MIGRATE_PFN_WRITE)
+ entry = make_writable_migration_entry(
+ page_to_pfn(page));
+ else
+ entry = make_readable_migration_entry(
+ page_to_pfn(page));
swp_pte = swp_entry_to_pte(entry);
if (pte_present(pte)) {
if (pte_soft_dirty(pte))
@@ -2965,7 +2974,12 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
if (is_device_private_page(page)) {
swp_entry_t swp_entry;

- swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
+ if (vma->vm_flags & VM_WRITE)
+ swp_entry = make_writable_device_private_entry(
+ page_to_pfn(page));
+ else
+ swp_entry = make_readable_device_private_entry(
+ page_to_pfn(page));
entry = swp_entry_to_pte(swp_entry);
}
} else {
diff --git a/mm/mprotect.c b/mm/mprotect.c
index ab709023e9aa..a6c757d87789 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -143,23 +143,25 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
swp_entry_t entry = pte_to_swp_entry(oldpte);
pte_t newpte;

- if (is_write_migration_entry(entry)) {
+ if (is_writable_migration_entry(entry)) {
/*
* A protection check is difficult so
* just be safe and disable write
*/
- make_migration_entry_read(&entry);
+ entry = make_readable_migration_entry(
+ swp_offset(entry));
newpte = swp_entry_to_pte(entry);
if (pte_swp_soft_dirty(oldpte))
newpte = pte_swp_mksoft_dirty(newpte);
if (pte_swp_uffd_wp(oldpte))
newpte = pte_swp_mkuffd_wp(newpte);
- } else if (is_write_device_private_entry(entry)) {
+ } else if (is_writable_device_private_entry(entry)) {
/*
* We do not preserve soft-dirtiness. See
* copy_one_pte() for explanation.
*/
- make_device_private_entry_read(&entry);
+ entry = make_readable_device_private_entry(
+ swp_offset(entry));
newpte = swp_entry_to_pte(entry);
if (pte_swp_uffd_wp(oldpte))
newpte = pte_swp_mkuffd_wp(newpte);
diff --git a/mm/rmap.c b/mm/rmap.c
index 08c56aaf72eb..ef9ef2694c58 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1512,7 +1512,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
* pte. do_swap_page() will wait until the migration
* pte is removed and then restart fault handling.
*/
- entry = make_migration_entry(page, 0);
+ entry = make_readable_migration_entry(page_to_pfn(page));
swp_pte = swp_entry_to_pte(entry);

/*
@@ -1608,8 +1608,12 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
* pte. do_swap_page() will wait until the migration
* pte is removed and then restart fault handling.
*/
- entry = make_migration_entry(subpage,
- pte_write(pteval));
+ if (pte_write(pteval))
+ entry = make_writable_migration_entry(
+ page_to_pfn(subpage));
+ else
+ entry = make_readable_migration_entry(
+ page_to_pfn(subpage));
swp_pte = swp_entry_to_pte(entry);
if (pte_soft_dirty(pteval))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
--
2.20.1

Next message: Alistair Popple: "[PATCH v3 3/8] mm/rmap: Split try_to_munlock from try_to_unmap"
Previous message: Alistair Popple: "[PATCH v3 1/8] mm: Remove special swap entry functions"
In reply to: Christoph Hellwig: "Re: [PATCH v3 1/8] mm: Remove special swap entry functions"
Next in thread: Christoph Hellwig: "Re: [PATCH v3 2/8] mm/swapops: Rework swap entry manipulation code"
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