From b5ff8161e37cef3265e186ecded23324e4dc2973 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Fri, 8 Sep 2017 16:10:49 -0700 Subject: [PATCH] mm: thp: introduce separate TTU flag for thp freezing 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) { ... /* PMD-mapped THP migration entry */ if (!pvmw.pte && (flags & TTU_MIGRATION)) { if (!PageAnon(page)) continue; set_pmd_migration_entry(&pvmw, page); continue; } ... } 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(). Link: http://lkml.kernel.org/r/20170717193955.20207-4-zi.yan@sent.com Signed-off-by: Naoya Horiguchi Signed-off-by: Zi Yan Acked-by: Kirill A. Shutemov Cc: "H. Peter Anvin" Cc: Anshuman Khandual Cc: Dave Hansen Cc: David Nellans Cc: Ingo Molnar Cc: Mel Gorman Cc: Minchan Kim Cc: Thomas Gleixner Cc: Vlastimil Babka Cc: Andrea Arcangeli Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/rmap.h | 3 ++- mm/huge_memory.c | 2 +- mm/rmap.c | 7 ++++--- 3 files changed, 7 insertions(+), 5 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 43ef2c3..f8ca2e7 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -93,8 +93,9 @@ enum ttu_flags { TTU_BATCH_FLUSH = 0x40, /* Batch TLB flushes where possible * and caller guarantees they will * do a final flush if necessary */ - TTU_RMAP_LOCKED = 0x80 /* do not grab rmap lock: + TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock: * caller holds it */ + TTU_SPLIT_FREEZE = 0x100, /* freeze pte under splitting thp */ }; #ifdef CONFIG_MMU diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 0b51e70..8a97833 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2210,7 +2210,7 @@ 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; unmap_success = try_to_unmap(page, ttu_flags); VM_BUG_ON_PAGE(!unmap_success, page); diff --git a/mm/rmap.c b/mm/rmap.c index c570f82..5b26af8a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1348,7 +1348,7 @@ static bool 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); } /* @@ -1445,7 +1445,7 @@ static bool 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; /* @@ -1575,7 +1575,8 @@ bool 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) -- 2.7.4