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From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, David Hildenbrand <david@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Muchun Song <muchun.song@linux.dev>
Subject: [PATCH v1 1/6] mm/rmap: drop stale comment in page_add_anon_rmap and hugepage_add_anon_rmap()
Date: Wed, 13 Sep 2023 14:51:08 +0200	[thread overview]
Message-ID: <20230913125113.313322-2-david@redhat.com> (raw)
In-Reply-To: <20230913125113.313322-1-david@redhat.com>

That comment was added in commit 5dbe0af47f8a ("mm: fix kernel BUG at
mm/rmap.c:1017!") to document why we can see vma->vm_end getting
adjusted concurrently due to a VMA split.

However, the optimized locking code was changed again in bf181b9f9d8
("mm anon rmap: replace same_anon_vma linked list with an interval tree.").

... and later, the comment was changed in commit 0503ea8f5ba7 ("mm/mmap:
remove __vma_adjust()") to talk about "vma_merge" although the original
issue was with VMA splitting.

Let's just remove that comment. Nowadays, it's outdated, imprecise and
confusing.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/rmap.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index ec7f8e6c9e48..ca2787c1fe05 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1245,7 +1245,6 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
 		__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
 
 	if (likely(!folio_test_ksm(folio))) {
-		/* address might be in next vma when migration races vma_merge */
 		if (first)
 			__page_set_anon_rmap(folio, page, vma, address,
 					     !!(flags & RMAP_EXCLUSIVE));
@@ -2536,7 +2535,6 @@ void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
 
 	BUG_ON(!folio_test_locked(folio));
 	BUG_ON(!anon_vma);
-	/* address might be in next vma when migration races vma_merge */
 	first = atomic_inc_and_test(&folio->_entire_mapcount);
 	VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page);
 	VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page);
-- 
2.41.0



  reply	other threads:[~2023-09-13 12:51 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-13 12:51 [PATCH v1 0/6] Anon rmap cleanups David Hildenbrand
2023-09-13 12:51 ` David Hildenbrand [this message]
2023-09-13 12:51 ` [PATCH v1 2/6] mm/rmap: move SetPageAnonExclusive out of __page_set_anon_rmap() David Hildenbrand
2023-09-13 14:32   ` Matthew Wilcox
2023-09-13 14:34     ` David Hildenbrand
2023-09-13 12:51 ` [PATCH v1 3/6] mm/rmap: move folio_test_anon() check out of __folio_set_anon() David Hildenbrand
2023-09-13 12:51 ` [PATCH v1 4/6] mm/rmap: warn on new PTE-mapped folios in page_add_anon_rmap() David Hildenbrand
2023-09-13 12:51 ` [PATCH v1 5/6] mm/rmap: simplify PageAnonExclusive sanity checks when adding anon rmap David Hildenbrand
2023-09-18  9:59   ` David Hildenbrand
2023-09-13 12:51 ` [PATCH v1 6/6] mm/rmap: pass folio to hugepage_add_anon_rmap() David Hildenbrand

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