[PATCH -V6 16/21] swap: Free PMD swap mapping when zap_huge_pmd()

Huang Ying
2018-10-10T07:28:12Z

For a PMD swap mapping, zap_huge_pmd() will clear the PMD and call
free_swap_and_cache() to decrease the swap reference count and maybe
free or split the huge swap cluster and the THP in swap cache.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
---
mm/huge_memory.c | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 74c8621619cb..b9c766683ee1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2066,7 +2066,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
spin_unlock(ptl);
if (is_huge_zero_pmd(orig_pmd))
tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
- } else if (is_huge_zero_pmd(orig_pmd)) {
+ } else if (pmd_present(orig_pmd) && is_huge_zero_pmd(orig_pmd)) {
zap_deposited_table(tlb->mm, pmd);
spin_unlock(ptl);
tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
@@ -2079,17 +2079,27 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
page_remove_rmap(page, true);
VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
VM_BUG_ON_PAGE(!PageHead(page), page);
- } else if (thp_migration_supported()) {
- swp_entry_t entry;
-
- VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
- entry = pmd_to_swp_entry(orig_pmd);
- page = pfn_to_page(swp_offset(entry));
+ } else {
+ swp_entry_t entry = pmd_to_swp_entry(orig_pmd);
+
+ if (thp_migration_supported() &&
+ is_migration_entry(entry))
+ page = pfn_to_page(swp_offset(entry));
+ else if (IS_ENABLED(CONFIG_THP_SWAP) &&
+ !non_swap_entry(entry))
+ free_swap_and_cache(entry, HPAGE_PMD_NR);
+ else {
+ WARN_ONCE(1,
+"Non present huge pmd without pmd migration or swap enabled!");
+ goto unlock;
+ }
flush_needed = 0;
- } else
- WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
+ }

- if (PageAnon(page)) {
+ if (!page) {
+ zap_deposited_table(tlb->mm, pmd);
+ add_mm_counter(tlb->mm, MM_SWAPENTS, -HPAGE_PMD_NR);
+ } else if (PageAnon(page)) {
zap_deposited_table(tlb->mm, pmd);
add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
} else {
@@ -2097,7 +2107,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
zap_deposited_table(tlb->mm, pmd);
add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
}
-
+unlock:
spin_unlock(ptl);
if (flush_needed)
tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
--
2.16.4