linux-kernel - [PATCH v2 6/8] mm/huge_memory: remove stale NUMA hinting comment from follow_trans_huge

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Message-ID: <20230801124844.278698-7-david@redhat.com>
Date:   Tue,  1 Aug 2023 14:48:42 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        liubo <liubo254@...wei.com>, Peter Xu <peterx@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        John Hubbard <jhubbard@...dia.com>,
        Mel Gorman <mgorman@...e.de>, Shuah Khan <shuah@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH v2 6/8] mm/huge_memory: remove stale NUMA hinting comment from follow_trans_huge_pmd()

That comment for pmd_protnone() was added in commit 2b4847e73004
("mm: numa: serialise parallel get_user_page against THP migration"), which
noted:

	THP does not unmap pages due to a lack of support for migration
	entries at a PMD level.  This allows races with get_user_pages

Nowadays, we do have PMD migration entries, so the comment no longer
applies. Let's drop it.

Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/huge_memory.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2cd3e5502180..0b709d2c46c6 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1467,7 +1467,6 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
 	if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
 		return ERR_PTR(-EFAULT);
 
-	/* Full NUMA hinting faults to serialise migration in fault paths */
 	if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags))
 		return NULL;
 
-- 
2.41.0