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Subject[PATCH -mm v2 04/11] pagewalk: move pmd_trans_huge_lock() from callbacks to common code
Date
Now all of current users of page table walker are canonicalized, i.e.
pmd_entry() handles only trans_pmd entry, and pte_entry() handles pte entry.
So we can factorize common code more.
This patch moves pmd_trans_huge_lock() in each pmd_entry() to pagewalk core.

ChangeLog v2:
- add null check walk->vma in walk_pmd_range()
- move comment update into a separate patch

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
arch/powerpc/mm/subpage-prot.c | 2 ++
fs/proc/task_mmu.c | 66 ++++++++++++++----------------------------
mm/memcontrol.c | 55 ++++++++++-------------------------
mm/pagewalk.c | 18 ++++++++++--
4 files changed, 55 insertions(+), 86 deletions(-)

diff --git mmotm-2014-05-21-16-57.orig/arch/powerpc/mm/subpage-prot.c mmotm-2014-05-21-16-57/arch/powerpc/mm/subpage-prot.c
index fa9fb5b4c66c..d0d94ac606f3 100644
--- mmotm-2014-05-21-16-57.orig/arch/powerpc/mm/subpage-prot.c
+++ mmotm-2014-05-21-16-57/arch/powerpc/mm/subpage-prot.c
@@ -135,7 +135,9 @@ static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
struct vm_area_struct *vma = walk->vma;
+ spin_unlock(walk->ptl);
split_huge_page_pmd(vma, addr, pmd);
+ spin_lock(walk->ptl);
return 0;
}

diff --git mmotm-2014-05-21-16-57.orig/fs/proc/task_mmu.c mmotm-2014-05-21-16-57/fs/proc/task_mmu.c
index fa6d6a4e85b3..059206ea3c6b 100644
--- mmotm-2014-05-21-16-57.orig/fs/proc/task_mmu.c
+++ mmotm-2014-05-21-16-57/fs/proc/task_mmu.c
@@ -496,15 +496,8 @@ static int smaps_pmd(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
struct mem_size_stats *mss = walk->private;
- spinlock_t *ptl;
-
- if (pmd_trans_huge_lock(pmd, walk->vma, &ptl) == 1) {
- smaps_pte((pte_t *)pmd, addr, addr + HPAGE_PMD_SIZE, walk);
- spin_unlock(ptl);
- mss->anonymous_thp += HPAGE_PMD_SIZE;
- /* don't call smaps_pte() */
- walk->skip = 1;
- }
+ smaps_pte((pte_t *)pmd, addr, addr + HPAGE_PMD_SIZE, walk);
+ mss->anonymous_thp += HPAGE_PMD_SIZE;
return 0;
}

@@ -983,31 +976,21 @@ static int pagemap_pmd(pmd_t *pmd, unsigned long addr, unsigned long end,
struct vm_area_struct *vma = walk->vma;
struct pagemapread *pm = walk->private;
pagemap_entry_t pme = make_pme(PM_NOT_PRESENT(pm->v2));
- spinlock_t *ptl;
-
- if (!vma)
- return err;
- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
- int pmd_flags2;
+ int pmd_flags2;

- if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(*pmd))
- pmd_flags2 = __PM_SOFT_DIRTY;
- else
- pmd_flags2 = 0;
+ if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(*pmd))
+ pmd_flags2 = __PM_SOFT_DIRTY;
+ else
+ pmd_flags2 = 0;

- for (; addr != end; addr += PAGE_SIZE) {
- unsigned long offset;
+ for (; addr != end; addr += PAGE_SIZE) {
+ unsigned long offset;

- offset = (addr & ~PAGEMAP_WALK_MASK) >>
- PAGE_SHIFT;
- thp_pmd_to_pagemap_entry(&pme, pm, *pmd, offset, pmd_flags2);
- err = add_to_pagemap(addr, &pme, pm);
- if (err)
- break;
- }
- spin_unlock(ptl);
- /* don't call pagemap_pte() */
- walk->skip = 1;
+ offset = (addr & ~PAGEMAP_WALK_MASK) >> PAGE_SHIFT;
+ thp_pmd_to_pagemap_entry(&pme, pm, *pmd, offset, pmd_flags2);
+ err = add_to_pagemap(addr, &pme, pm);
+ if (err)
+ break;
}
return err;
}
@@ -1277,20 +1260,13 @@ static int gather_pmd_stats(pmd_t *pmd, unsigned long addr,
{
struct numa_maps *md = walk->private;
struct vm_area_struct *vma = walk->vma;
- spinlock_t *ptl;
-
- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
- pte_t huge_pte = *(pte_t *)pmd;
- struct page *page;
-
- page = can_gather_numa_stats(huge_pte, vma, addr);
- if (page)
- gather_stats(page, md, pte_dirty(huge_pte),
- HPAGE_PMD_SIZE/PAGE_SIZE);
- spin_unlock(ptl);
- /* don't call gather_pte_stats() */
- walk->skip = 1;
- }
+ pte_t huge_pte = *(pte_t *)pmd;
+ struct page *page;
+
+ page = can_gather_numa_stats(huge_pte, vma, addr);
+ if (page)
+ gather_stats(page, md, pte_dirty(huge_pte),
+ HPAGE_PMD_SIZE/PAGE_SIZE);
return 0;
}
#ifdef CONFIG_HUGETLB_PAGE
diff --git mmotm-2014-05-21-16-57.orig/mm/memcontrol.c mmotm-2014-05-21-16-57/mm/memcontrol.c
index 01a66a208769..bb987cb9e043 100644
--- mmotm-2014-05-21-16-57.orig/mm/memcontrol.c
+++ mmotm-2014-05-21-16-57/mm/memcontrol.c
@@ -6723,15 +6723,9 @@ static int mem_cgroup_count_precharge_pmd(pmd_t *pmd,
struct mm_walk *walk)
{
struct vm_area_struct *vma = walk->vma;
- spinlock_t *ptl;
-
- if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
- if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
- mc.precharge += HPAGE_PMD_NR;
- spin_unlock(ptl);
- /* don't call mem_cgroup_count_precharge_pte() */
- walk->skip = 1;
- }
+
+ if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
+ mc.precharge += HPAGE_PMD_NR;
return 0;
}

@@ -6952,38 +6946,21 @@ static int mem_cgroup_move_charge_pmd(pmd_t *pmd,
struct page *page;
struct page_cgroup *pc;

- /*
- * 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 (mc.precharge < HPAGE_PMD_NR) {
- spin_unlock(ptl);
- return 0;
- }
- target_type = get_mctgt_type_thp(vma, addr, *pmd, &target);
- if (target_type == MC_TARGET_PAGE) {
- page = target.page;
- if (!isolate_lru_page(page)) {
- pc = lookup_page_cgroup(page);
- if (!mem_cgroup_move_account(page, HPAGE_PMD_NR,
- pc, mc.from, mc.to)) {
- mc.precharge -= HPAGE_PMD_NR;
- mc.moved_charge += HPAGE_PMD_NR;
- }
- putback_lru_page(page);
+ if (mc.precharge < HPAGE_PMD_NR)
+ return 0;
+ target_type = get_mctgt_type_thp(vma, addr, *pmd, &target);
+ if (target_type == MC_TARGET_PAGE) {
+ page = target.page;
+ if (!isolate_lru_page(page)) {
+ pc = lookup_page_cgroup(page);
+ if (!mem_cgroup_move_account(page, HPAGE_PMD_NR,
+ pc, mc.from, mc.to)) {
+ mc.precharge -= HPAGE_PMD_NR;
+ mc.moved_charge += HPAGE_PMD_NR;
}
- put_page(page);
+ putback_lru_page(page);
}
- spin_unlock(ptl);
- /* don't call mem_cgroup_move_charge_pte() */
- walk->skip = 1;
+ put_page(page);
}
return 0;
}
diff --git mmotm-2014-05-21-16-57.orig/mm/pagewalk.c mmotm-2014-05-21-16-57/mm/pagewalk.c
index 24311d6f5c20..f1a3417d0b51 100644
--- mmotm-2014-05-21-16-57.orig/mm/pagewalk.c
+++ mmotm-2014-05-21-16-57/mm/pagewalk.c
@@ -73,8 +73,22 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr,
continue;
}

- if (walk->pmd_entry) {
- err = walk->pmd_entry(pmd, addr, next, walk);
+ /*
+ * 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 (walk->pmd_entry && walk->vma) {
+ if (pmd_trans_huge_lock(pmd, walk->vma, &walk->ptl) == 1) {
+ err = walk->pmd_entry(pmd, addr, next, walk);
+ spin_unlock(walk->ptl);
+ }
if (skip_lower_level_walking(walk))
continue;
if (err)
--
1.9.3


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