linux-kernel - [PATCH 30/36] thp: add option to setup migration entiries during PMD split

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Message-Id: <1436550130-112636-31-git-send-email-kirill.shutemov@linux.intel.com>
Date:	Fri, 10 Jul 2015 20:42:04 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Dave Hansen <dave.hansen@...el.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Steve Capper <steve.capper@...aro.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 30/36] thp: add option to setup migration entiries during PMD split

We are going to use migration PTE entires to stabilize page counts.
If the page is mapped with PMDs we need to split the PMD and setup
migration enties. It's reasonable to combine these operations to avoid
double-scanning over the page table.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Tested-by: Sasha Levin <sasha.levin@...cle.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/huge_memory.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 46daa1dc3dc0..affbabaf31bd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -24,6 +24,7 @@
 #include <linux/migrate.h>
 #include <linux/hashtable.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/swapops.h>
 
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
@@ -2576,7 +2577,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
 }
 
 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
-		unsigned long haddr)
+		unsigned long haddr, bool freeze)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct page *page;
@@ -2614,12 +2615,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 		 * transferred to avoid any possibility of altering
 		 * permissions across VMAs.
 		 */
-		entry = mk_pte(page + i, vma->vm_page_prot);
-		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-		if (!write)
-			entry = pte_wrprotect(entry);
-		if (!young)
-			entry = pte_mkold(entry);
+		if (freeze) {
+			swp_entry_t swp_entry;
+			swp_entry = make_migration_entry(page + i, write);
+			entry = swp_entry_to_pte(swp_entry);
+		} else {
+			entry = mk_pte(page + i, vma->vm_page_prot);
+			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+			if (!write)
+				entry = pte_wrprotect(entry);
+			if (!young)
+				entry = pte_mkold(entry);
+		}
 		pte = pte_offset_map(&_pmd, haddr);
 		BUG_ON(!pte_none(*pte));
 		set_pte_at(mm, haddr, pte, entry);
@@ -2670,7 +2677,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 	mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
 	ptl = pmd_lock(mm, pmd);
 	if (likely(pmd_trans_huge(*pmd)))
-		__split_huge_pmd_locked(vma, pmd, haddr);
+		__split_huge_pmd_locked(vma, pmd, haddr, false);
 	spin_unlock(ptl);
 	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
 }
-- 
2.1.4

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