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Subject[PATCHv4 15/24] mm, thp: remove infrastructure for handling splitting PMDs
Date
With new refcounting we don't need to mark PMDs splitting. Let's drop code
to handle this.

Arch-specific code will removed separately.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
fs/proc/task_mmu.c | 8 +++---
include/asm-generic/pgtable.h | 5 ----
include/linux/huge_mm.h | 16 ------------
mm/gup.c | 7 ------
mm/huge_memory.c | 57 +++++++++----------------------------------
mm/memcontrol.c | 14 ++---------
mm/memory.c | 18 ++------------
mm/mincore.c | 2 +-
mm/pgtable-generic.c | 14 -----------
mm/rmap.c | 4 +--
10 files changed, 21 insertions(+), 124 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 50acf17538db..fcd1b887eccc 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -534,7 +534,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
pte_t *pte;
spinlock_t *ptl;

- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
smaps_pmd_entry(pmd, addr, walk);
spin_unlock(ptl);
return 0;
@@ -799,7 +799,7 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
spinlock_t *ptl;
struct page *page;

- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
clear_soft_dirty_pmd(vma, addr, pmd);
goto out;
@@ -1112,7 +1112,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
pte_t *pte, *orig_pte;
int err = 0;

- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
int pmd_flags2;

if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(*pmd))
@@ -1416,7 +1416,7 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
pte_t *orig_pte;
pte_t *pte;

- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
pte_t huge_pte = *(pte_t *)pmd;
struct page *page;

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 1f9f5da6828f..8a89bb60d6f5 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -183,11 +183,6 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif

-#ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH
-extern void pmdp_splitting_flush(struct vm_area_struct *vma,
- unsigned long address, pmd_t *pmdp);
-#endif
-
#ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
pgtable_t pgtable);
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 3c5fe722cc14..7a0c477a2b38 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -49,15 +49,9 @@ enum transparent_hugepage_flag {
#endif
};

-enum page_check_address_pmd_flag {
- PAGE_CHECK_ADDRESS_PMD_FLAG,
- PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG,
- PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG,
-};
extern pmd_t *page_check_address_pmd(struct page *page,
struct mm_struct *mm,
unsigned long address,
- enum page_check_address_pmd_flag flag,
spinlock_t **ptl);
extern int pmd_freeable(pmd_t pmd);

@@ -110,14 +104,6 @@ extern void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
if (unlikely(pmd_trans_huge(*____pmd))) \
__split_huge_pmd(__vma, __pmd, __address); \
} while (0)
-#define wait_split_huge_page(__anon_vma, __pmd) \
- do { \
- pmd_t *____pmd = (__pmd); \
- anon_vma_lock_write(__anon_vma); \
- anon_vma_unlock_write(__anon_vma); \
- BUG_ON(pmd_trans_splitting(*____pmd) || \
- pmd_trans_huge(*____pmd)); \
- } while (0)
#if HPAGE_PMD_ORDER >= MAX_ORDER
#error "hugepages can't be allocated by the buddy allocator"
#endif
@@ -184,8 +170,6 @@ static inline int split_huge_page(struct page *page)
{
return 0;
}
-#define wait_split_huge_page(__anon_vma, __pmd) \
- do { } while (0)
#define split_huge_pmd(__vma, __pmd, __address) \
do { } while (0)
static inline int hugepage_madvise(struct vm_area_struct *vma,
diff --git a/mm/gup.c b/mm/gup.c
index b68d9ffa3c9e..2f776850108c 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -208,13 +208,6 @@ struct page *follow_page_mask(struct vm_area_struct *vma,
spin_unlock(ptl);
return follow_page_pte(vma, address, pmd, flags);
}
-
- if (unlikely(pmd_trans_splitting(*pmd))) {
- spin_unlock(ptl);
- wait_split_huge_page(vma->anon_vma, pmd);
- return follow_page_pte(vma, address, pmd, flags);
- }
-
if (flags & FOLL_SPLIT) {
int ret;
page = pmd_page(*pmd);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 6f6429426edb..3741f81e423e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -880,15 +880,6 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
goto out_unlock;
}

- if (unlikely(pmd_trans_splitting(pmd))) {
- /* split huge page running from under us */
- spin_unlock(src_ptl);
- spin_unlock(dst_ptl);
- pte_free(dst_mm, pgtable);
-
- wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
- goto out;
- }
src_page = pmd_page(pmd);
VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
get_page(src_page);
@@ -1392,7 +1383,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
spinlock_t *ptl;
int ret = 0;

- if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (__pmd_trans_huge_lock(pmd, vma, &ptl)) {
struct page *page;
pgtable_t pgtable;
pmd_t orig_pmd;
@@ -1432,7 +1423,6 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
pmd_t *old_pmd, pmd_t *new_pmd)
{
spinlock_t *old_ptl, *new_ptl;
- int ret = 0;
pmd_t pmd;

struct mm_struct *mm = vma->vm_mm;
@@ -1441,7 +1431,7 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
(new_addr & ~HPAGE_PMD_MASK) ||
old_end - old_addr < HPAGE_PMD_SIZE ||
(new_vma->vm_flags & VM_NOHUGEPAGE))
- goto out;
+ return 0;

/*
* The destination pmd shouldn't be established, free_pgtables()
@@ -1449,15 +1439,14 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
*/
if (WARN_ON(!pmd_none(*new_pmd))) {
VM_BUG_ON(pmd_trans_huge(*new_pmd));
- goto out;
+ return 0;
}

/*
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_sem prevents deadlock.
*/
- ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl);
- if (ret == 1) {
+ if (__pmd_trans_huge_lock(old_pmd, vma, &old_ptl)) {
new_ptl = pmd_lockptr(mm, new_pmd);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
@@ -1473,9 +1462,9 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
+ return 1;
}
-out:
- return ret;
+ return 0;
}

/*
@@ -1491,7 +1480,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
spinlock_t *ptl;
int ret = 0;

- if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (__pmd_trans_huge_lock(pmd, vma, &ptl)) {
pmd_t entry;

/*
@@ -1529,17 +1518,8 @@ int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
spinlock_t **ptl)
{
*ptl = pmd_lock(vma->vm_mm, pmd);
- if (likely(pmd_trans_huge(*pmd))) {
- if (unlikely(pmd_trans_splitting(*pmd))) {
- spin_unlock(*ptl);
- wait_split_huge_page(vma->anon_vma, pmd);
- return -1;
- } else {
- /* Thp mapped by 'pmd' is stable, so we can
- * handle it as it is. */
- return 1;
- }
- }
+ if (likely(pmd_trans_huge(*pmd)))
+ return 1;
spin_unlock(*ptl);
return 0;
}
@@ -1555,7 +1535,6 @@ int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
pmd_t *page_check_address_pmd(struct page *page,
struct mm_struct *mm,
unsigned long address,
- enum page_check_address_pmd_flag flag,
spinlock_t **ptl)
{
pgd_t *pgd;
@@ -1578,21 +1557,8 @@ pmd_t *page_check_address_pmd(struct page *page,
goto unlock;
if (pmd_page(*pmd) != page)
goto unlock;
- /*
- * split_vma() may create temporary aliased mappings. There is
- * no risk as long as all huge pmd are found and have their
- * splitting bit set before __split_huge_page_refcount
- * runs. Finding the same huge pmd more than once during the
- * same rmap walk is not a problem.
- */
- if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
- pmd_trans_splitting(*pmd))
- goto unlock;
- if (pmd_trans_huge(*pmd)) {
- VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
- !pmd_trans_splitting(*pmd));
+ if (pmd_trans_huge(*pmd))
return pmd;
- }
unlock:
spin_unlock(*ptl);
return NULL;
@@ -1926,8 +1892,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
mmun_end = haddr + HPAGE_PMD_SIZE;
mmu_notifier_invalidate_range_start(vma->vm_mm,
mmun_start, mmun_end);
- pmd = page_check_address_pmd(page, vma->vm_mm, addr,
- PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
+ pmd = page_check_address_pmd(page, vma->vm_mm, addr, &ptl);
if (pmd) {
__split_huge_pmd_locked(vma, pmd, addr);
spin_unlock(ptl);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0c86945bcc9a..0724cd50b48a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4903,7 +4903,7 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
pte_t *pte;
spinlock_t *ptl;

- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
mc.precharge += HPAGE_PMD_NR;
spin_unlock(ptl);
@@ -5071,17 +5071,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
union mc_target target;
struct page *page;

- /*
- * We don't take compound_lock() here but no race with splitting thp
- * happens because:
- * - if pmd_trans_huge_lock() returns 1, the relevant thp is not
- * under splitting, which means there's no concurrent thp split,
- * - if another thread runs into split_huge_page() just after we
- * entered this if-block, the thread must wait for page table lock
- * to be unlocked in __split_huge_page_splitting(), where the main
- * part of thp split is not executed yet.
- */
- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
if (mc.precharge < HPAGE_PMD_NR) {
spin_unlock(ptl);
return 0;
diff --git a/mm/memory.c b/mm/memory.c
index 0db0481311d5..e7a08de704b4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -565,7 +565,6 @@ int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
{
spinlock_t *ptl;
pgtable_t new = pte_alloc_one(mm, address);
- int wait_split_huge_page;
if (!new)
return -ENOMEM;

@@ -585,18 +584,14 @@ int __pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */

ptl = pmd_lock(mm, pmd);
- wait_split_huge_page = 0;
if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
atomic_long_inc(&mm->nr_ptes);
pmd_populate(mm, pmd, new);
new = NULL;
- } else if (unlikely(pmd_trans_splitting(*pmd)))
- wait_split_huge_page = 1;
+ }
spin_unlock(ptl);
if (new)
pte_free(mm, new);
- if (wait_split_huge_page)
- wait_split_huge_page(vma->anon_vma, pmd);
return 0;
}

@@ -612,8 +607,7 @@ int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
pmd_populate_kernel(&init_mm, pmd, new);
new = NULL;
- } else
- VM_BUG_ON(pmd_trans_splitting(*pmd));
+ }
spin_unlock(&init_mm.page_table_lock);
if (new)
pte_free_kernel(&init_mm, new);
@@ -3284,14 +3278,6 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (pmd_trans_huge(orig_pmd)) {
unsigned int dirty = flags & FAULT_FLAG_WRITE;

- /*
- * If the pmd is splitting, return and retry the
- * the fault. Alternative: wait until the split
- * is done, and goto retry.
- */
- if (pmd_trans_splitting(orig_pmd))
- return 0;
-
if (pmd_protnone(orig_pmd))
return do_huge_pmd_numa_page(mm, vma, address,
orig_pmd, pmd);
diff --git a/mm/mincore.c b/mm/mincore.c
index be25efde64a4..feb867f5fdf4 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -117,7 +117,7 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
unsigned char *vec = walk->private;
int nr = (end - addr) >> PAGE_SHIFT;

- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
memset(vec, 1, nr);
spin_unlock(ptl);
goto out;
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index c25f94b33811..2fe699cedd4d 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -133,20 +133,6 @@ pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
#endif

-#ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
- pmd_t *pmdp)
-{
- pmd_t pmd = pmd_mksplitting(*pmdp);
- VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- set_pmd_at(vma->vm_mm, address, pmdp, pmd);
- /* tlb flush only to serialize against gup-fast */
- flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
-}
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-#endif
-
#ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
diff --git a/mm/rmap.c b/mm/rmap.c
index db8b99e48966..eb2f4a0d3961 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -730,8 +730,7 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
* rmap might return false positives; we must filter
* these out using page_check_address_pmd().
*/
- pmd = page_check_address_pmd(page, mm, address,
- PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
+ pmd = page_check_address_pmd(page, mm, address, &ptl);
if (!pmd)
return SWAP_AGAIN;

@@ -741,7 +740,6 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
return SWAP_FAIL; /* To break the loop */
}

- /* go ahead even if the pmd is pmd_trans_splitting() */
if (pmdp_clear_flush_young_notify(vma, address, pmd))
referenced++;

--
2.1.4


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