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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, david@redhat.com, linux-mm@kvack.org,
	mhocko@suse.com, mike.kravetz@oracle.com,
	mm-commits@vger.kernel.org, osalvador@suse.de,
	shy828301@gmail.com, songmuchun@bytedance.com,
	torvalds@linux-foundation.org
Subject: [patch 05/18] mm: migrate: do not migrate HugeTLB page whose refcount is one
Date: Thu, 04 Feb 2021 18:32:17 -0800	[thread overview]
Message-ID: <20210205023217.P0pR8PLuH%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210204183135.e123f0d6027529f2cf500cf2@linux-foundation.org>

From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: migrate: do not migrate HugeTLB page whose refcount is one

All pages isolated for the migration have an elevated reference count and
therefore seeing a reference count equal to 1 means that the last user of
the page has dropped the reference and the page has became unused and
there doesn't make much sense to migrate it anymore.  This has been done
for regular pages and this patch does the same for hugetlb pages. 
Although the likelihood of the race is rather small for hugetlb pages it
makes sense the two code paths in sync.

Link: https://lkml.kernel.org/r/20210115124942.46403-2-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Yang Shi <shy828301@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/mm/migrate.c~mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one
+++ a/mm/migrate.c
@@ -1280,6 +1280,12 @@ static int unmap_and_move_huge_page(new_
 		return -ENOSYS;
 	}
 
+	if (page_count(hpage) == 1) {
+		/* page was freed from under us. So we are done. */
+		putback_active_hugepage(hpage);
+		return MIGRATEPAGE_SUCCESS;
+	}
+
 	new_hpage = get_new_page(hpage, private);
 	if (!new_hpage)
 		return -ENOMEM;
_


  parent reply	other threads:[~2021-02-05  2:32 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-05  2:31 incoming Andrew Morton
2021-02-05  2:32 ` [patch 01/18] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page Andrew Morton
2021-02-05  2:32 ` [patch 02/18] mm: hugetlb: fix a race between freeing and dissolving the page Andrew Morton
2021-02-05  2:32 ` [patch 03/18] mm: hugetlb: fix a race between isolating and freeing page Andrew Morton
2021-02-05  2:32 ` [patch 04/18] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge_active Andrew Morton
2021-02-05  2:32 ` Andrew Morton [this message]
2021-02-05  2:32 ` [patch 06/18] mm, compaction: move high_pfn to the for loop scope Andrew Morton
2021-02-05  2:32 ` [patch 07/18] mm/vmalloc: separate put pages and flush VM flags Andrew Morton
2021-02-05  2:32 ` [patch 08/18] init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov Andrew Morton
2021-02-05  2:32 ` [patch 09/18] mm: thp: fix MADV_REMOVE deadlock on shmem THP Andrew Morton
2021-02-05  2:32 ` [patch 10/18] memblock: do not start bottom-up allocations with kernel_end Andrew Morton
2021-02-05  2:32 ` [patch 11/18] mailmap: fix name/email for Viresh Kumar Andrew Morton
2021-02-05  2:32 ` [patch 12/18] mailmap: add entries for Manivannan Sadhasivam Andrew Morton
2021-02-05  2:32 ` [patch 13/18] mm/filemap: add missing mem_cgroup_uncharge() to __add_to_page_cache_locked() Andrew Morton
2021-02-05  2:32 ` [patch 14/18] kasan: add explicit preconditions to kasan_report() Andrew Morton
2021-02-05  2:32 ` [patch 15/18] kasan: make addr_has_metadata() return true for valid addresses Andrew Morton
2021-02-05  2:32 ` [patch 16/18] ubsan: implement __ubsan_handle_alignment_assumption Andrew Morton
2021-02-05  2:33 ` [patch 17/18] mm: hugetlb: fix missing put_page in gather_surplus_pages() Andrew Morton
2021-02-05  2:33 ` [patch 18/18] MAINTAINERS/.mailmap: use my @kernel.org address Andrew Morton

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