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From: "Huang, Ying" <ying.huang@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Huang Ying <ying.huang@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	David Hildenbrand <david@redhat.com>,
	Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
	Zi Yan <ziy@nvidia.com>, Michal Hocko <mhocko@kernel.org>,
	Minchan Kim <minchan@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Hugh Dickins <hughd@google.com>
Subject: [RFC 1/3] mm, migrate: Check return value of try_to_unmap()
Date: Fri, 28 Feb 2020 11:38:17 +0800	[thread overview]
Message-ID: <20200228033819.3857058-2-ying.huang@intel.com> (raw)
In-Reply-To: <20200228033819.3857058-1-ying.huang@intel.com>

From: Huang Ying <ying.huang@intel.com>

During the page migration, try_to_unmap() is called to replace the
page table entries with the migration entries.  Now its return value
is ignored, that is generally OK in most cases.  But in theory, it's
possible that try_to_unmap() return false (failure) for the page
migration after arch_unmap_one() is called in unmap code.  Even if
without arch_unmap_one(), it makes code more robust for the future
code changing to check the return value.

Known issue: I don't know what is the appropriate error code for
try_to_unmap() failure.  Whether EIO is OK?

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
---
 mm/migrate.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 3900044cfaa6..981f8374a6ef 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1116,8 +1116,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
 		/* Establish migration ptes */
 		VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
 				page);
-		try_to_unmap(page,
-			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
+		if (!try_to_unmap(page,
+			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS)) {
+			rc = -EIO;
+			goto out_unlock_both;
+		}
 		page_was_mapped = 1;
 	}
 
@@ -1337,8 +1340,11 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 		goto put_anon;
 
 	if (page_mapped(hpage)) {
-		try_to_unmap(hpage,
-			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
+		if (!try_to_unmap(hpage,
+			TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS)) {
+			rc = -EIO;
+			goto unlock_both;
+		}
 		page_was_mapped = 1;
 	}
 
@@ -1349,6 +1355,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
 		remove_migration_ptes(hpage,
 			rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false);
 
+unlock_both:
 	unlock_page(new_hpage);
 
 put_anon:
@@ -2558,8 +2565,7 @@ static void migrate_vma_unmap(struct migrate_vma *migrate)
 			continue;
 
 		if (page_mapped(page)) {
-			try_to_unmap(page, flags);
-			if (page_mapped(page))
+			if (!try_to_unmap(page, flags))
 				goto restore;
 		}
 
-- 
2.25.0



  reply	other threads:[~2020-02-28  3:38 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-28  3:38 [RFC 0/3] mm: Discard lazily freed pages when migrating Huang, Ying
2020-02-28  3:38 ` Huang, Ying [this message]
2020-02-28  3:38 ` [RFC 2/3] mm: Add a new page flag PageLayzyFree() for MADV_FREE Huang, Ying
2020-02-28  6:13   ` David Hildenbrand
2020-02-28  6:47     ` Huang, Ying
2020-03-15  8:18   ` Wei Yang
2020-03-15  8:54     ` Mika Penttilä
2020-03-15 12:22       ` Wei Yang
2020-03-16  1:21         ` Huang, Ying
2020-03-16 22:38           ` Wei Yang
2020-02-28  3:38 ` [RFC 3/3] mm: Discard lazily freed pages when migrating Huang, Ying
2020-02-28  3:42 ` [RFC 0/3] " Matthew Wilcox
2020-02-28  7:25   ` Huang, Ying
2020-02-28  8:22     ` David Hildenbrand
2020-02-28  8:55       ` Huang, Ying
2020-02-28  9:49         ` Mel Gorman
2020-03-02 11:23           ` Huang, Ying
2020-03-02 15:16             ` Mel Gorman
2020-03-03  1:51               ` Huang, Ying
2020-03-03  8:09                 ` Michal Hocko
2020-03-03  8:47                   ` Huang, Ying
2020-03-03  8:58                     ` Michal Hocko
2020-03-03 11:49                       ` Huang, Ying
2020-03-04  9:58                         ` Michal Hocko
2020-03-04 10:56                           ` Mel Gorman
2020-03-05  1:42                             ` Huang, Ying
2020-03-04 11:15                           ` Huang, Ying
2020-03-04 11:26                             ` Michal Hocko
2020-03-05  1:45                               ` Huang, Ying
2020-03-05 10:48                             ` Mel Gorman
2020-03-06  4:05                               ` Huang, Ying
2020-03-09  5:26                               ` Huang, Ying
2020-03-03 13:02                 ` Mel Gorman
2020-03-04  0:33                   ` Huang, Ying
2020-02-28  9:50         ` Michal Hocko
2020-02-28 10:15           ` Michal Hocko
2020-02-28 13:45           ` Johannes Weiner
2020-03-02 14:12           ` Huang, Ying
2020-03-02 14:23             ` David Hildenbrand
2020-03-03  0:25               ` Huang, Ying
2020-03-02 14:25             ` Michal Hocko
2020-03-03  1:30               ` Huang, Ying
2020-03-03  8:19                 ` Michal Hocko
2020-03-03 11:36                   ` Huang, Ying

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