linux-kernel - [PATCHv5 24/28] thp, mm: split_huge

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Date:	Fri, 24 Apr 2015 00:03:59 +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: [PATCHv5 24/28] thp, mm: split_huge_page(): caller need to lock page

We're going to use migration entries instead of compound_lock() to
stabilize page refcounts. Setup and remove migration entries require
page to be locked.

Some of split_huge_page() callers already have the page locked. Let's
require everybody to lock the page before calling split_huge_page().

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Tested-by: Sasha Levin <sasha.levin@...cle.com>
---
 mm/memory-failure.c | 12 +++++++++---
 mm/migrate.c        |  8 ++++++--
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 441eff52d099..d9b06727e480 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -996,7 +996,10 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 		 * enough * to be safe.
 		 */
 		if (!PageHuge(hpage) && PageAnon(hpage)) {
-			if (unlikely(split_huge_page(hpage))) {
+			lock_page(hpage);
+			ret = split_huge_page(hpage);
+			unlock_page(hpage);
+			if (unlikely(ret)) {
 				/*
 				 * FIXME: if splitting THP is failed, it is
 				 * better to stop the following operation rather
@@ -1750,10 +1753,13 @@ int soft_offline_page(struct page *page, int flags)
 		return -EBUSY;
 	}
 	if (!PageHuge(page) && PageTransHuge(hpage)) {
-		if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
+		lock_page(page);
+		ret = split_huge_page(hpage);
+		unlock_page(page);
+		if (unlikely(ret)) {
 			pr_info("soft offline: %#lx: failed to split THP\n",
 				pfn);
-			return -EBUSY;
+			return ret;
 		}
 	}
 
diff --git a/mm/migrate.c b/mm/migrate.c
index b51e88c9dba2..03b9c4ba56dc 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -932,9 +932,13 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
 		goto out;
 	}
 
-	if (unlikely(PageTransHuge(page)))
-		if (unlikely(split_huge_page(page)))
+	if (unlikely(PageTransHuge(page))) {
+		lock_page(page);
+		rc = split_huge_page(page);
+		unlock_page(page);
+		if (rc)
 			goto out;
+	}
 
 	rc = __unmap_and_move(page, newpage, force, mode);
 
-- 
2.1.4

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