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From: Zi Yan <zi.yan@sent.com>
To: kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Cc: akpm@linux-foundation.org, minchan@kernel.org, vbabka@suse.cz,
	mgorman@techsingularity.net, mhocko@kernel.org,
	khandual@linux.vnet.ibm.com, zi.yan@cs.rutgers.edu,
	dnellans@nvidia.com, dave.hansen@intel.com,
	n-horiguchi@ah.jp.nec.com
Subject: [PATCH v8 03/10] mm: thp: introduce separate TTU flag for thp freezing
Date: Sat,  1 Jul 2017 09:40:01 -0400	[thread overview]
Message-ID: <20170701134008.110579-4-zi.yan@sent.com> (raw)
In-Reply-To: <20170701134008.110579-1-zi.yan@sent.com>

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 (!pvmw.pte && page) {
                  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().

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 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 43ef2c30cb0f..f8ca2e74b819 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 86975dec0ba1..35711b35b067 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2167,7 +2167,7 @@ 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 2324c923c813..91948fbbb0bb 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1308,7 +1308,7 @@ 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);
 	}
 
 	while (page_vma_mapped_walk(&pvmw)) {
@@ -1397,7 +1397,7 @@ 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;
 			/*
@@ -1522,7 +1522,8 @@ 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)
-- 
2.11.0

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  parent reply	other threads:[~2017-07-01 13:41 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-01 13:39 [PATCH v8 00/10] mm: page migration enhancement for thp Zi Yan
2017-07-01 13:39 ` [PATCH v8 01/10] mm: mempolicy: add queue_pages_required() Zi Yan
2017-07-01 13:40 ` [PATCH v8 02/10] mm: x86: move _PAGE_SWP_SOFT_DIRTY from bit 7 to bit 1 Zi Yan
2017-07-01 13:40 ` Zi Yan [this message]
2017-07-01 13:40 ` [PATCH v8 04/10] mm: thp: introduce CONFIG_ARCH_ENABLE_THP_MIGRATION Zi Yan
2017-07-01 13:40 ` [PATCH v8 05/10] mm: thp: enable thp migration in generic path Zi Yan
2017-07-02 17:57   ` Kirill A. Shutemov
2017-07-03  1:26     ` Zi Yan
2017-07-11  6:47   ` Naoya Horiguchi
2017-07-11 14:00     ` Zi Yan
2017-07-13  9:30       ` Naoya Horiguchi
2017-07-13 11:28         ` Zi Yan
2017-07-14  0:06           ` Naoya Horiguchi
2017-07-01 13:40 ` [PATCH v8 06/10] mm: thp: check pmd migration entry in common path Zi Yan
2017-07-14  9:29   ` Naoya Horiguchi
2017-07-14 18:29     ` Zi Yan
2017-07-01 13:40 ` [PATCH v8 07/10] mm: soft-dirty: keep soft-dirty bits over thp migration Zi Yan
2017-07-01 13:40 ` [PATCH v8 08/10] mm: mempolicy: mbind and migrate_pages support " Zi Yan
2017-07-01 13:40 ` [PATCH v8 09/10] mm: migrate: move_pages() supports " Zi Yan
2017-07-01 13:40 ` [PATCH v8 10/10] mm: memory_hotplug: memory hotremove " Zi Yan

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