[PATCH v2 02/32] mm/migrate: remove cruft from migration_entry_wait()s

Hugh Dickins
2023-06-09T01:08:28Z

migration_entry_wait_on_locked() does not need to take a mapped pte
pointer, its callers can do the unmap first. Annotate it with
__releases(ptl) to reduce sparse warnings.

Fold __migration_entry_wait_huge() into migration_entry_wait_huge().
Fold __migration_entry_wait() into migration_entry_wait(), preferring
the tighter pte_offset_map_lock() to pte_offset_map() and pte_lockptr().

Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
---
include/linux/migrate.h | 4 ++--
include/linux/swapops.h | 17 +++--------------
mm/filemap.c | 13 ++++---------
mm/migrate.c | 37 +++++++++++++------------------------
4 files changed, 22 insertions(+), 49 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 6241a1596a75..affea3063473 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -75,8 +75,8 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode);

int migrate_huge_page_move_mapping(struct address_space *mapping,
struct folio *dst, struct folio *src);
-void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
- spinlock_t *ptl);
+void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
+ __releases(ptl);
void folio_migrate_flags(struct folio *newfolio, struct folio *folio);
void folio_migrate_copy(struct folio *newfolio, struct folio *folio);
int folio_migrate_mapping(struct address_space *mapping,
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 3a451b7afcb3..4c932cb45e0b 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -332,15 +332,9 @@ static inline bool is_migration_entry_dirty(swp_entry_t entry)
return false;
}

-extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
- spinlock_t *ptl);
extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
unsigned long address);
-#ifdef CONFIG_HUGETLB_PAGE
-extern void __migration_entry_wait_huge(struct vm_area_struct *vma,
- pte_t *ptep, spinlock_t *ptl);
extern void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte);
-#endif /* CONFIG_HUGETLB_PAGE */
#else /* CONFIG_MIGRATION */
static inline swp_entry_t make_readable_migration_entry(pgoff_t offset)
{
@@ -362,15 +356,10 @@ static inline int is_migration_entry(swp_entry_t swp)
return 0;
}

-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) { }
-#ifdef CONFIG_HUGETLB_PAGE
-static inline void __migration_entry_wait_huge(struct vm_area_struct *vma,
- pte_t *ptep, spinlock_t *ptl) { }
-static inline void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte) { }
-#endif /* CONFIG_HUGETLB_PAGE */
+ unsigned long address) { }
+static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
+ pte_t *pte) { }
static inline int is_writable_migration_entry(swp_entry_t entry)
{
return 0;
diff --git a/mm/filemap.c b/mm/filemap.c
index b4c9bd368b7e..28b42ee848a4 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1359,8 +1359,6 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
/**
* migration_entry_wait_on_locked - Wait for a migration entry to be removed
* @entry: migration swap entry.
- * @ptep: mapped pte pointer. Will return with the ptep unmapped. Only required
- * for pte entries, pass NULL for pmd entries.
* @ptl: already locked ptl. This function will drop the lock.
*
* Wait for a migration entry referencing the given page to be removed. This is
@@ -1369,13 +1367,13 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
* should be called while holding the ptl for the migration entry referencing
* the page.
*
- * Returns after unmapping and unlocking the pte/ptl with pte_unmap_unlock().
+ * Returns after unlocking the ptl.
*
* This follows the same logic as folio_wait_bit_common() so see the comments
* there.
*/
-void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
- spinlock_t *ptl)
+void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
+ __releases(ptl)
{
struct wait_page_queue wait_page;
wait_queue_entry_t *wait = &wait_page.wait;
@@ -1409,10 +1407,7 @@ void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep,
* a valid reference to the page, and it must take the ptl to remove the
* migration entry. So the page is valid until the ptl is dropped.
*/
- if (ptep)
- pte_unmap_unlock(ptep, ptl);
- else
- spin_unlock(ptl);
+ spin_unlock(ptl);

for (;;) {
unsigned int flags;
diff --git a/mm/migrate.c b/mm/migrate.c
index 01cac26a3127..3ecb7a40075f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -296,14 +296,18 @@ void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked)
* get to the page and wait until migration is finished.
* When we return from this function the fault will be retried.
*/
-void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
- spinlock_t *ptl)
+void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
+ unsigned long address)
{
+ spinlock_t *ptl;
+ pte_t *ptep;
pte_t pte;
swp_entry_t entry;

- spin_lock(ptl);
+ ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
pte = *ptep;
+ pte_unmap(ptep);
+
if (!is_swap_pte(pte))
goto out;

@@ -311,18 +315,10 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
if (!is_migration_entry(entry))
goto out;

- migration_entry_wait_on_locked(entry, ptep, ptl);
+ migration_entry_wait_on_locked(entry, ptl);
return;
out:
- pte_unmap_unlock(ptep, ptl);
-}
-
-void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
- unsigned long address)
-{
- spinlock_t *ptl = pte_lockptr(mm, pmd);
- pte_t *ptep = pte_offset_map(pmd, address);
- __migration_entry_wait(mm, ptep, ptl);
+ spin_unlock(ptl);
}

#ifdef CONFIG_HUGETLB_PAGE
@@ -332,9 +328,9 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
*
* This function will release the vma lock before returning.
*/
-void __migration_entry_wait_huge(struct vm_area_struct *vma,
- pte_t *ptep, spinlock_t *ptl)
+void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *ptep)
{
+ spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, ptep);
pte_t pte;

hugetlb_vma_assert_locked(vma);
@@ -352,16 +348,9 @@ void __migration_entry_wait_huge(struct vm_area_struct *vma,
* lock release in migration_entry_wait_on_locked().
*/
hugetlb_vma_unlock_read(vma);
- migration_entry_wait_on_locked(pte_to_swp_entry(pte), NULL, ptl);
+ migration_entry_wait_on_locked(pte_to_swp_entry(pte), ptl);
}
}
-
-void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte)
-{
- spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, pte);
-
- __migration_entry_wait_huge(vma, pte, ptl);
-}
#endif

#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
@@ -372,7 +361,7 @@ 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;
- migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), NULL, ptl);
+ migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), ptl);
return;
unlock:
spin_unlock(ptl);
--
2.35.3