From: David Hildenbrand <david@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <muchun.song@linux.dev>
Subject: Re: [PATCH v1 2/6] mm/rmap: move SetPageAnonExclusive out of __page_set_anon_rmap()
Date: Wed, 13 Sep 2023 16:34:06 +0200 [thread overview]
Message-ID: <3142b596-43d9-7c6d-cdcc-59137d0f2ca1@redhat.com> (raw)
In-Reply-To: <ZQHH6ZC9aHQaqlNJ@casper.infradead.org>
On 13.09.23 16:32, Matthew Wilcox wrote:
> On Wed, Sep 13, 2023 at 02:51:09PM +0200, David Hildenbrand wrote:
>> @@ -1246,11 +1241,13 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
>>
>> if (likely(!folio_test_ksm(folio))) {
>> if (first)
>> - __page_set_anon_rmap(folio, page, vma, address,
>> - !!(flags & RMAP_EXCLUSIVE));
>> + __folio_set_anon(folio, vma, address,
>> + !!(flags & RMAP_EXCLUSIVE));
>> else
>> __page_check_anon_rmap(folio, page, vma, address);
>> }
>> + if (flags & RMAP_EXCLUSIVE)
>> + SetPageAnonExclusive(page);
>
> Won't we end up setting AnonExclusive on ksm pages, or do we make sure
> to never pass RMAP_EXCLUSIVE for ksm pages?
Not if there is a bug and someone passes RMAP_EXCLUSIVE for these. :)
Fortunately, we do have
VM_BUG_ON_PGFLAGS(!PageAnon(page) || PageKsm(page), page);
in SetPageAnonExclusive() to catch such bugs.
>
> Maybe better to move these last two lines inside the previous test,
> just to avoid the question.
That could end up hiding another BUG, so I'd rather let
SetPageAnonExclusive() catch it.
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2023-09-13 14:34 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 ` [PATCH v1 1/6] mm/rmap: drop stale comment in page_add_anon_rmap and hugepage_add_anon_rmap() David Hildenbrand
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 [this message]
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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