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Subject[PATCHv12 25/37] 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.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
---
fs/proc/task_mmu.c | 8 +++---
include/asm-generic/pgtable.h | 9 ------
include/linux/huge_mm.h | 21 ++++----------
mm/gup.c | 12 +-------
mm/huge_memory.c | 67 +++++++++++--------------------------------
mm/memcontrol.c | 13 ++-------
mm/memory.c | 18 ++----------
mm/mincore.c | 2 +-
mm/mremap.c | 15 +++++-----
mm/page_idle.c | 3 +-
mm/pgtable-generic.c | 14 ---------
mm/rmap.c | 4 +--
12 files changed, 41 insertions(+), 145 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ace02a4a07db..d7ffe5db55ce 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -564,7 +564,7 @@ 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;
@@ -852,7 +852,7 @@ 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;
@@ -1126,7 +1126,7 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
int err = 0;

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- if (pmd_trans_huge_lock(pmdp, vma, &ptl) == 1) {
+ if (pmd_trans_huge_lock(pmdp, vma, &ptl)) {
u64 flags = 0, frame = 0;
pmd_t pmd = *pmdp;

@@ -1458,7 +1458,7 @@ 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 29c57b2cb344..010a7e3f6ad1 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -184,11 +184,6 @@ 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 pmdp_collapse_flush
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
@@ -586,10 +581,6 @@ static inline int pmd_trans_huge(pmd_t pmd)
{
return 0;
}
-static inline int pmd_trans_splitting(pmd_t pmd)
-{
- return 0;
-}
#ifndef __HAVE_ARCH_PMD_WRITE
static inline int pmd_write(pmd_t pmd)
{
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 87ea3723ff04..b82c0c2a96f6 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -28,7 +28,7 @@ extern int zap_huge_pmd(struct mmu_gather *tlb,
extern int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
unsigned char *vec);
-extern int move_huge_pmd(struct vm_area_struct *vma,
+extern bool move_huge_pmd(struct vm_area_struct *vma,
struct vm_area_struct *new_vma,
unsigned long old_addr,
unsigned long new_addr, unsigned long old_end,
@@ -51,15 +51,9 @@ 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);

@@ -104,7 +98,6 @@ extern unsigned long transparent_hugepage_flags;
#define split_huge_page(page) BUILD_BUG()
#define split_huge_pmd(__vma, __pmd, __address) BUILD_BUG()

-#define wait_split_huge_page(__anon_vma, __pmd) BUILD_BUG()
#if HPAGE_PMD_ORDER >= MAX_ORDER
#error "hugepages can't be allocated by the buddy allocator"
#endif
@@ -114,17 +107,17 @@ extern void vma_adjust_trans_huge(struct vm_area_struct *vma,
unsigned long start,
unsigned long end,
long adjust_next);
-extern int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
+extern bool __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
spinlock_t **ptl);
/* mmap_sem must be held on entry */
-static inline int pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
+static inline bool pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
spinlock_t **ptl)
{
VM_BUG_ON_VMA(!rwsem_is_locked(&vma->vm_mm->mmap_sem), vma);
if (pmd_trans_huge(*pmd))
return __pmd_trans_huge_lock(pmd, vma, ptl);
else
- return 0;
+ return false;
}
static inline int hpage_nr_pages(struct page *page)
{
@@ -169,8 +162,6 @@ 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,
@@ -185,10 +176,10 @@ static inline void vma_adjust_trans_huge(struct vm_area_struct *vma,
long adjust_next)
{
}
-static inline int pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
+static inline bool pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
spinlock_t **ptl)
{
- return 0;
+ return false;
}

static inline int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
diff --git a/mm/gup.c b/mm/gup.c
index 7017abea9fd6..70d65e4015a4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -241,13 +241,6 @@ 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);
@@ -1068,9 +1061,6 @@ struct page *get_dump_page(unsigned long addr)
* *) HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table is used to free
* pages containing page tables.
*
- * *) THP splits will broadcast an IPI, this can be achieved by overriding
- * pmdp_splitting_flush.
- *
* *) ptes can be read atomically by the architecture.
*
* *) access_ok is sufficient to validate userspace address ranges.
@@ -1267,7 +1257,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
pmd_t pmd = READ_ONCE(*pmdp);

next = pmd_addr_end(addr, end);
- if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+ if (pmd_none(pmd))
return 0;

if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) {
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 065449872d1b..149e2548fa5e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1017,15 +1017,6 @@ 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);
@@ -1531,7 +1522,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t orig_pmd;
spinlock_t *ptl;

- if (__pmd_trans_huge_lock(pmd, vma, &ptl) != 1)
+ if (!__pmd_trans_huge_lock(pmd, vma, &ptl))
return 0;
/*
* For architectures like ppc64 we look at deposited pgtable
@@ -1565,13 +1556,12 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
return 1;
}

-int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
+bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
unsigned long old_addr,
unsigned long new_addr, unsigned long old_end,
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;
@@ -1580,7 +1570,7 @@ 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 false;

/*
* The destination pmd shouldn't be established, free_pgtables()
@@ -1588,15 +1578,14 @@ 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 false;
}

/*
* 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);
@@ -1612,9 +1601,9 @@ 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 true;
}
-out:
- return ret;
+ return false;
}

/*
@@ -1630,7 +1619,7 @@ 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;
bool preserve_write = prot_numa && pmd_write(*pmd);
ret = 1;
@@ -1661,29 +1650,19 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
}

/*
- * Returns 1 if a given pmd maps a stable (not under splitting) thp.
- * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
+ * Returns true if a given pmd maps a thp, false otherwise.
*
- * Note that if it returns 1, this routine returns without unlocking page
- * table locks. So callers must unlock them.
+ * Note that if it returns true, this routine returns without unlocking page
+ * table lock. So callers must unlock it.
*/
-int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
+bool __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 true;
spin_unlock(*ptl);
- return 0;
+ return false;
}

/*
@@ -1697,7 +1676,6 @@ 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;
@@ -1720,21 +1698,8 @@ 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;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 33c486e8dc7c..e2b04eeb9a59 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4727,7 +4727,7 @@ 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);
@@ -4898,16 +4898,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
union mc_target target;
struct page *page;

- /*
- * 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 facbb15c986c..3ae5ed168d00 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -566,7 +566,6 @@ 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;

@@ -586,18 +585,14 @@ 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;
}

@@ -613,8 +608,7 @@ 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);
@@ -3365,14 +3359,6 @@ 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 14bb9fb37f0c..2a565ed8bb49 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/mremap.c b/mm/mremap.c
index b3cd29bd1a60..9acf51a4f682 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -192,25 +192,24 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
if (!new_pmd)
break;
if (pmd_trans_huge(*old_pmd)) {
- int err = 0;
if (extent == HPAGE_PMD_SIZE) {
+ bool moved;
VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma,
vma);
/* See comment in move_ptes() */
if (need_rmap_locks)
anon_vma_lock_write(vma->anon_vma);
- err = move_huge_pmd(vma, new_vma, old_addr,
+ moved = move_huge_pmd(vma, new_vma, old_addr,
new_addr, old_end,
old_pmd, new_pmd);
if (need_rmap_locks)
anon_vma_unlock_write(vma->anon_vma);
+ if (moved) {
+ need_flush = true;
+ continue;
+ }
}
- if (err > 0) {
- need_flush = true;
- continue;
- } else if (!err) {
- split_huge_pmd(vma, old_pmd, old_addr);
- }
+ split_huge_pmd(vma, old_pmd, old_addr);
VM_BUG_ON(pmd_trans_huge(*old_pmd));
}
if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
diff --git a/mm/page_idle.c b/mm/page_idle.c
index d5dd79041484..1c245d9027e3 100644
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -61,8 +61,7 @@ static int page_idle_clear_pte_refs_one(struct page *page,
bool referenced = false;

if (unlikely(PageTransHuge(page))) {
- pmd = page_check_address_pmd(page, mm, addr,
- PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
+ pmd = page_check_address_pmd(page, mm, addr, &ptl);
if (pmd) {
referenced = pmdp_clear_young_notify(vma, addr, pmd);
spin_unlock(ptl);
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 6b674e00153c..89b150f8c920 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -134,20 +134,6 @@ pmd_t pmdp_huge_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 294be04c7e38..d4d7a1fe0b1d 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -843,8 +843,7 @@ 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;

@@ -854,7 +853,6 @@ 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++;

--
2.5.3


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