linux-kernel - [PATCH 6.6 05/60] mm: migrate: remove PageTransHuge check in numamigrate_isolate

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Message-ID: <20240313163707.615000-6-sashal@kernel.org>
Date: Wed, 13 Mar 2024 12:36:12 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Kefeng Wang <wangkefeng.wang@...wei.com>,
	Matthew Wilcox <willy@...radead.org>,
	David Hildenbrand <david@...hat.com>,
	Huang Ying <ying.huang@...el.com>,
	Hugh Dickins <hughd@...gle.com>,
	Mike Kravetz <mike.kravetz@...cle.com>,
	Zi Yan <ziy@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.6 05/60] mm: migrate: remove PageTransHuge check in numamigrate_isolate_page()

From: Kefeng Wang <wangkefeng.wang@...wei.com>

[ Upstream commit a8ac4a767dcd9d87d8229045904d9fe15ea5e0e8 ]

Patch series "mm: migrate: more folio conversion and unification", v3.

Convert more migrate functions to use a folio, it is also a preparation
for large folio migration support when balancing numa.

This patch (of 8):

The assert VM_BUG_ON_PAGE(order && !PageTransHuge(page), page) is not very
useful,

   1) for a tail/base page, order = 0, for a head page, the order > 0 &&
      PageTransHuge() is true
   2) there is a PageCompound() check and only base page is handled in
      do_numa_page(), and do_huge_pmd_numa_page() only handle PMD-mapped
      THP
   3) even though the page is a tail page, isolate_lru_page() will post
      a warning, and fail to isolate the page
   4) if large folio/pte-mapped THP migration supported in the future,
      we could migrate the entire folio if numa fault on a tail page

so just remove the check.

Link: https://lkml.kernel.org/r/20230913095131.2426871-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20230913095131.2426871-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
Suggested-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Zi Yan <ziy@...dia.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Stable-dep-of: 2774f256e7c0 ("mm/vmscan: fix a bug calling wakeup_kswapd() with a wrong zone index")
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/migrate.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index b4d972d80b10c..6f8ad6b64c9bc 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2506,8 +2506,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
 	int nr_pages = thp_nr_pages(page);
 	int order = compound_order(page);
 
-	VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
-
 	/* Do not migrate THP mapped by multiple processes */
 	if (PageTransHuge(page) && total_mapcount(page) > 1)
 		return 0;
-- 
2.43.0