Commit 992ba0c8 authored by Gavin Shan's avatar Gavin Shan Committed by Liu Shixin
Browse files

mm: migrate: fix THP's mapcount on isolation 

mainline inclusion
from mainline-v6.1-rc8
commit 829ae0f8
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAR7B3

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=829ae0f81ce093d674ff2256f66a714753e9ce32

--------------------------------

The issue is reported when removing memory through virtio_mem device.  The
transparent huge page, experienced copy-on-write fault, is wrongly
regarded as pinned.  The transparent huge page is escaped from being
isolated in isolate_migratepages_block().  The transparent huge page can't
be migrated and the corresponding memory block can't be put into offline
state.

Fix it by replacing page_mapcount() with total_mapcount().  With this, the
transparent huge page can be isolated and migrated, and the memory block
can be put into offline state.  Besides, The page's refcount is increased
a bit earlier to avoid the page is released when the check is executed.

Link: https://lkml.kernel.org/r/20221124095523.31061-1-gshan@redhat.com


Fixes: 1da2f328 ("mm,thp,compaction,cma: allow THP migration for CMA allocations")
Signed-off-by: default avatarGavin Shan <gshan@redhat.com>
Reported-by: default avatarZhenyu Zhang <zhenyzha@redhat.com>
Tested-by: default avatarZhenyu Zhang <zhenyzha@redhat.com>
Suggested-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>	[5.7+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Conflicts:
	mm/compaction.c
[ Context conflicts. ]
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 2a8f63a1

mm/compaction.c

+11 −11
Original line number Diff line number Diff line
@@ -965,29 +965,29 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, 
			goto isolate_fail;

		}



		/*

		 * Be careful not to clear PageLRU until after we're

		 * sure the page is not being freed elsewhere -- the

		 * page release code relies on it.

		 */

		if (unlikely(!get_page_unless_zero(page)))

			goto isolate_fail;



		/*

		 * Migration will fail if an anonymous page is pinned in memory,

		 * so avoid taking lru_lock and isolating it unnecessarily in an

		 * admittedly racy check.

		 */

		if (!page_mapping(page) &&

		    page_count(page) > page_mapcount(page))

			goto isolate_fail;

		    (page_count(page) - 1) > total_mapcount(page))

			goto isolate_fail_put;



		/*

		 * Only allow to migrate anonymous pages in GFP_NOFS context

		 * because those do not depend on fs locks.

		 */

		if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page))

			goto isolate_fail;



		/*

		 * Be careful not to clear PageLRU until after we're

		 * sure the page is not being freed elsewhere -- the

		 * page release code relies on it.

		 */

		if (unlikely(!get_page_unless_zero(page)))

			goto isolate_fail;

			goto isolate_fail_put;



		if (__isolate_lru_page_prepare(page, isolate_mode) != 0)

			goto isolate_fail_put;