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Subject[PATCH v2 5/5] mm: factor out pmd young/dirty bit handling and THP split
Date
Now, there are common part among MADV_COLD|PAGEOUT|FREE to reset
access/dirty bit resetting or split the THP page to handle part
of subpages in the THP page. This patch factor out the common part.

Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Christopher Lameter <cl@linux.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
include/linux/huge_mm.h | 3 -
mm/huge_memory.c | 74 -------------
mm/madvise.c | 234 +++++++++++++++++++++++-----------------
3 files changed, 135 insertions(+), 176 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 7cd5c150c21d..2667e1aa3ce5 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -29,9 +29,6 @@ extern struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
unsigned long addr,
pmd_t *pmd,
unsigned int flags);
-extern bool madvise_free_huge_pmd(struct mmu_gather *tlb,
- struct vm_area_struct *vma,
- pmd_t *pmd, unsigned long addr, unsigned long next);
extern int zap_huge_pmd(struct mmu_gather *tlb,
struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9f8bce9a6b32..22e20f929463 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1668,80 +1668,6 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
return 0;
}

-/*
- * Return true if we do MADV_FREE successfully on entire pmd page.
- * Otherwise, return false.
- */
-bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
- pmd_t *pmd, unsigned long addr, unsigned long next)
-{
- spinlock_t *ptl;
- pmd_t orig_pmd;
- struct page *page;
- struct mm_struct *mm = tlb->mm;
- bool ret = false;
-
- tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
-
- ptl = pmd_trans_huge_lock(pmd, vma);
- if (!ptl)
- goto out_unlocked;
-
- orig_pmd = *pmd;
- if (is_huge_zero_pmd(orig_pmd))
- goto out;
-
- if (unlikely(!pmd_present(orig_pmd))) {
- VM_BUG_ON(thp_migration_supported() &&
- !is_pmd_migration_entry(orig_pmd));
- goto out;
- }
-
- page = pmd_page(orig_pmd);
- /*
- * If other processes are mapping this page, we couldn't discard
- * the page unless they all do MADV_FREE so let's skip the page.
- */
- if (page_mapcount(page) != 1)
- goto out;
-
- if (!trylock_page(page))
- goto out;
-
- /*
- * If user want to discard part-pages of THP, split it so MADV_FREE
- * will deactivate only them.
- */
- if (next - addr != HPAGE_PMD_SIZE) {
- get_page(page);
- spin_unlock(ptl);
- split_huge_page(page);
- unlock_page(page);
- put_page(page);
- goto out_unlocked;
- }
-
- if (PageDirty(page))
- ClearPageDirty(page);
- unlock_page(page);
-
- if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
- pmdp_invalidate(vma, addr, pmd);
- orig_pmd = pmd_mkold(orig_pmd);
- orig_pmd = pmd_mkclean(orig_pmd);
-
- set_pmd_at(mm, addr, pmd, orig_pmd);
- tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
- }
-
- mark_page_lazyfree(page);
- ret = true;
-out:
- spin_unlock(ptl);
-out_unlocked:
- return ret;
-}
-
static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
{
pgtable_t pgtable;
diff --git a/mm/madvise.c b/mm/madvise.c
index 3b9d2ba421b1..bb1906bb75fd 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -310,6 +310,91 @@ static long madvise_willneed(struct vm_area_struct *vma,
return 0;
}

+enum madv_pmdp_reset_t {
+ MADV_PMDP_RESET, /* pmd was reset successfully */
+ MADV_PMDP_SPLIT, /* pmd was split */
+ MADV_PMDP_ERROR,
+};
+
+static enum madv_pmdp_reset_t madvise_pmdp_reset_or_split(struct mm_walk *walk,
+ pmd_t *pmd, spinlock_t *ptl,
+ unsigned long addr, unsigned long end,
+ bool young, bool dirty)
+{
+ pmd_t orig_pmd;
+ unsigned long next;
+ struct page *page;
+ struct mmu_gather *tlb = walk->private;
+ struct mm_struct *mm = walk->mm;
+ struct vm_area_struct *vma = walk->vma;
+ bool reset_young = false;
+ bool reset_dirty = false;
+ enum madv_pmdp_reset_t ret = MADV_PMDP_ERROR;
+
+ orig_pmd = *pmd;
+ if (is_huge_zero_pmd(orig_pmd))
+ return ret;
+
+ if (unlikely(!pmd_present(orig_pmd))) {
+ VM_BUG_ON(thp_migration_supported() &&
+ !is_pmd_migration_entry(orig_pmd));
+ return ret;
+ }
+
+ next = pmd_addr_end(addr, end);
+ page = pmd_page(orig_pmd);
+ if (next - addr != HPAGE_PMD_SIZE) {
+ /*
+ * THP collapsing is not cheap so only split the page is
+ * private to the this process.
+ */
+ if (page_mapcount(page) != 1)
+ return ret;
+ get_page(page);
+ spin_unlock(ptl);
+ lock_page(page);
+ if (!split_huge_page(page))
+ ret = MADV_PMDP_SPLIT;
+ unlock_page(page);
+ put_page(page);
+ return ret;
+ }
+
+ if (young && pmd_young(orig_pmd))
+ reset_young = true;
+ if (dirty && pmd_dirty(orig_pmd))
+ reset_dirty = true;
+
+ /*
+ * Other process could rely on the PG_dirty for data consistency,
+ * not pte_dirty so we could reset PG_dirty only when we are owner
+ * of the page.
+ */
+ if (reset_dirty) {
+ if (page_mapcount(page) != 1)
+ goto out;
+ if (!trylock_page(page))
+ goto out;
+ if (PageDirty(page))
+ ClearPageDirty(page);
+ unlock_page(page);
+ }
+
+ ret = MADV_PMDP_RESET;
+ if (reset_young || reset_dirty) {
+ tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
+ pmdp_invalidate(vma, addr, pmd);
+ if (reset_young)
+ orig_pmd = pmd_mkold(orig_pmd);
+ if (reset_dirty)
+ orig_pmd = pmd_mkclean(orig_pmd);
+ set_pmd_at(mm, addr, pmd, orig_pmd);
+ tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+ }
+out:
+ return ret;
+}
+
static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
@@ -319,64 +404,31 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,
pte_t *orig_pte, *pte, ptent;
spinlock_t *ptl;
struct page *page;
- unsigned long next;

- next = pmd_addr_end(addr, end);
if (pmd_trans_huge(*pmd)) {
- pmd_t orig_pmd;
-
- tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
ptl = pmd_trans_huge_lock(pmd, vma);
if (!ptl)
return 0;

- orig_pmd = *pmd;
- if (is_huge_zero_pmd(orig_pmd))
- goto huge_unlock;
-
- if (unlikely(!pmd_present(orig_pmd))) {
- VM_BUG_ON(thp_migration_supported() &&
- !is_pmd_migration_entry(orig_pmd));
- goto huge_unlock;
- }
-
- page = pmd_page(orig_pmd);
- if (next - addr != HPAGE_PMD_SIZE) {
- int err;
-
- if (page_mapcount(page) != 1)
- goto huge_unlock;
-
- get_page(page);
+ switch (madvise_pmdp_reset_or_split(walk, pmd, ptl, addr, end,
+ true, false)) {
+ case MADV_PMDP_RESET:
spin_unlock(ptl);
- lock_page(page);
- err = split_huge_page(page);
- unlock_page(page);
- put_page(page);
- if (!err)
- goto regular_page;
- return 0;
- }
-
- if (pmd_young(orig_pmd)) {
- pmdp_invalidate(vma, addr, pmd);
- orig_pmd = pmd_mkold(orig_pmd);
-
- set_pmd_at(mm, addr, pmd, orig_pmd);
- tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+ page = pmd_page(*pmd);
+ test_and_clear_page_young(page);
+ deactivate_page(page);
+ goto next;
+ case MADV_PMDP_ERROR:
+ spin_unlock(ptl);
+ goto next;
+ case MADV_PMDP_SPLIT:
+ ; /* go through */
}
-
- test_and_clear_page_young(page);
- deactivate_page(page);
-huge_unlock:
- spin_unlock(ptl);
- return 0;
}

if (pmd_trans_unstable(pmd))
return 0;

-regular_page:
tlb_change_page_size(tlb, PAGE_SIZE);
orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
flush_tlb_batched_pending(mm);
@@ -414,6 +466,7 @@ static int madvise_cold_pte_range(pmd_t *pmd, unsigned long addr,

arch_enter_lazy_mmu_mode();
pte_unmap_unlock(orig_pte, ptl);
+next:
cond_resched();

return 0;
@@ -464,70 +517,38 @@ static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr,
LIST_HEAD(page_list);
struct page *page;
int isolated = 0;
- unsigned long next;

if (fatal_signal_pending(current))
return -EINTR;

- next = pmd_addr_end(addr, end);
if (pmd_trans_huge(*pmd)) {
- pmd_t orig_pmd;
-
- tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
ptl = pmd_trans_huge_lock(pmd, vma);
if (!ptl)
return 0;

- orig_pmd = *pmd;
- if (is_huge_zero_pmd(orig_pmd))
- goto huge_unlock;
-
- if (unlikely(!pmd_present(orig_pmd))) {
- VM_BUG_ON(thp_migration_supported() &&
- !is_pmd_migration_entry(orig_pmd));
- goto huge_unlock;
- }
-
- page = pmd_page(orig_pmd);
- if (next - addr != HPAGE_PMD_SIZE) {
- int err;
-
- if (page_mapcount(page) != 1)
- goto huge_unlock;
- get_page(page);
+ switch (madvise_pmdp_reset_or_split(walk, pmd, ptl, addr, end,
+ true, false)) {
+ case MADV_PMDP_RESET:
+ page = pmd_page(*pmd);
spin_unlock(ptl);
- lock_page(page);
- err = split_huge_page(page);
- unlock_page(page);
- put_page(page);
- if (!err)
- goto regular_page;
- return 0;
- }
-
- if (isolate_lru_page(page))
- goto huge_unlock;
-
- if (pmd_young(orig_pmd)) {
- pmdp_invalidate(vma, addr, pmd);
- orig_pmd = pmd_mkold(orig_pmd);
-
- set_pmd_at(mm, addr, pmd, orig_pmd);
- tlb_remove_tlb_entry(tlb, pmd, addr);
+ if (isolate_lru_page(page))
+ return 0;
+ ClearPageReferenced(page);
+ test_and_clear_page_young(page);
+ list_add(&page->lru, &page_list);
+ reclaim_pages(&page_list);
+ goto next;
+ case MADV_PMDP_ERROR:
+ spin_unlock(ptl);
+ goto next;
+ case MADV_PMDP_SPLIT:
+ ; /* go through */
}
-
- ClearPageReferenced(page);
- test_and_clear_page_young(page);
- list_add(&page->lru, &page_list);
-huge_unlock:
- spin_unlock(ptl);
- reclaim_pages(&page_list);
- return 0;
}

if (pmd_trans_unstable(pmd))
return 0;
-regular_page:
+
tlb_change_page_size(tlb, PAGE_SIZE);
orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
flush_tlb_batched_pending(mm);
@@ -569,6 +590,7 @@ static int madvise_pageout_pte_range(pmd_t *pmd, unsigned long addr,
arch_leave_lazy_mmu_mode();
pte_unmap_unlock(orig_pte, ptl);
reclaim_pages(&page_list);
+next:
cond_resched();

return 0;
@@ -620,12 +642,26 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
pte_t *orig_pte, *pte, ptent;
struct page *page;
int nr_swap = 0;
- unsigned long next;

- next = pmd_addr_end(addr, end);
- if (pmd_trans_huge(*pmd))
- if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next))
+ if (pmd_trans_huge(*pmd)) {
+ ptl = pmd_trans_huge_lock(pmd, vma);
+ if (!ptl)
+ return 0;
+
+ switch (madvise_pmdp_reset_or_split(walk, pmd, ptl, addr, end,
+ true, true)) {
+ case MADV_PMDP_RESET:
+ page = pmd_page(*pmd);
+ spin_unlock(ptl);
+ mark_page_lazyfree(page);
goto next;
+ case MADV_PMDP_ERROR:
+ spin_unlock(ptl);
+ goto next;
+ case MADV_PMDP_SPLIT:
+ ; /* go through */
+ }
+ }

if (pmd_trans_unstable(pmd))
return 0;
@@ -737,8 +773,8 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
}
arch_leave_lazy_mmu_mode();
pte_unmap_unlock(orig_pte, ptl);
- cond_resched();
next:
+ cond_resched();
return 0;
}

--
2.22.0.rc2.383.gf4fbbf30c2-goog
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