Messages in this thread Patch in this message | | | From | Zi Yan <> | Subject | [PATCH v3 06/14] mm: thp: introduce separate TTU flag for thp freezing | Date | Sun, 5 Feb 2017 11:12:44 -0500 |
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From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
TTU_MIGRATION is used to convert pte into migration entry until thp split completes. This behavior conflicts with thp migration added later patches, so let's introduce a new TTU flag specifically for freezing.
try_to_unmap() is used both for thp split (via freeze_page()) and page migration (via __unmap_and_move()). In freeze_page(), ttu_flag given for head page is like below (assuming anonymous thp):
(TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED | \ TTU_MIGRATION | TTU_SPLIT_HUGE_PMD)
and ttu_flag given for tail pages is:
(TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED | \ TTU_MIGRATION)
__unmap_and_move() calls try_to_unmap() with ttu_flag:
(TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS)
Now I'm trying to insert a branch for thp migration at the top of try_to_unmap_one() like below
static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, unsigned long address, void *arg) { ... if (flags & TTU_MIGRATION) { if (!PageHuge(page) && PageTransCompound(page)) { set_pmd_migration_entry(page, vma, address); goto out; } }
, so try_to_unmap() for tail pages called by thp split can go into thp migration code path (which converts *pmd* into migration entry), while the expectation is to freeze thp (which converts *pte* into migration entry.)
I detected this failure as a "bad page state" error in a testcase where split_huge_page() is called from queue_pages_pte_range().
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> --- include/linux/rmap.h | 1 + mm/huge_memory.c | 2 +- mm/rmap.c | 7 ++++--- 3 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 8c89e902df3e..97d8b7127bd2 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -88,6 +88,7 @@ enum ttu_flags { TTU_MUNLOCK = 4, /* munlock mode */ TTU_LZFREE = 8, /* lazy free mode */ TTU_SPLIT_HUGE_PMD = 16, /* split huge PMD if any */ + TTU_SPLIT_FREEZE = 32, /* freeze pte under splitting thp */ TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */ TTU_IGNORE_ACCESS = (1 << 9), /* don't age */ diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d8e15fd817b0..6893c47428b6 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2123,7 +2123,7 @@ static void freeze_page(struct page *page) VM_BUG_ON_PAGE(!PageHead(page), page); if (PageAnon(page)) - ttu_flags |= TTU_MIGRATION; + ttu_flags |= TTU_SPLIT_FREEZE; ret = try_to_unmap(page, ttu_flags); VM_BUG_ON_PAGE(ret, page); diff --git a/mm/rmap.c b/mm/rmap.c index 8774791e2809..16789b936e3a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1310,7 +1310,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if (flags & TTU_SPLIT_HUGE_PMD) { split_huge_pmd_address(vma, address, - flags & TTU_MIGRATION, page); + flags & TTU_SPLIT_FREEZE, page); } while (page_vma_mapped_walk(&pvmw)) { @@ -1395,7 +1395,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, */ dec_mm_counter(mm, mm_counter(page)); } else if (IS_ENABLED(CONFIG_MIGRATION) && - (flags & TTU_MIGRATION)) { + (flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) { swp_entry_t entry; pte_t swp_pte; /* @@ -1514,7 +1514,8 @@ int try_to_unmap(struct page *page, enum ttu_flags flags) * locking requirements of exec(), migration skips * temporary VMAs until after exec() completes. */ - if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page)) + if ((flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE)) + && !PageKsm(page) && PageAnon(page)) rwc.invalid_vma = invalid_migration_vma; if (flags & TTU_RMAP_LOCKED) -- 2.11.0
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