From: "David Hildenbrand (Red Hat)" <david@kernel.org>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: Harry Yoo <harry.yoo@oracle.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org,
"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
Will Deacon <will@kernel.org>,
"Aneesh Kumar K.V" <aneesh.kumar@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Nick Piggin <npiggin@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>,
Muchun Song <muchun.song@linux.dev>,
Oscar Salvador <osalvador@suse.de>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
Pedro Falcato <pfalcato@suse.de>, Rik van Riel <riel@surriel.com>,
Laurence Oberman <loberman@redhat.com>,
Prakash Sangappa <prakash.sangappa@oracle.com>,
Liu Shixin <liushixin2@huawei.com>
Subject: Re: [PATCH v2 2/4] mm/hugetlb: fix two comments related to huge_pmd_unshare()
Date: Sun, 21 Dec 2025 10:26:42 +0100 [thread overview]
Message-ID: <b4898184-ee7b-4e37-860e-5790339059a3@kernel.org> (raw)
In-Reply-To: <3D7F0E85-2509-4925-BDD5-149E9E8D5C1F@gmail.com>
>>>>
>>>> Whoever is the last owner of a (previously) shared page table must unmap any
>>>> contained pages (adjust mapcount/ref, sync a/d bit, ...).
>>> Right.
>>>> So it's not just a matter of deferring the freeing, because these page tables
>>>> will still contain content.
>>> I was (and maybe still) bit confused while reading the old comment as
>>> it implied (or maybe I just misread) that by deferring freeing of page tables
>>> we don't have to flush TLB in __unmap_hugepage_range() and can flush later
>>> instead.
>>
>> Yeah, I am also confused by the old comment. I think the idea there was to drop the reference only later and thereby deferred-free the page.
>
> My bad. I looked again, and the comment indeed doesn’t make much sense. Thanks for fixing it.
No worries, thanks for taking a look!
--
Cheers
David
next prev parent reply other threads:[~2025-12-21 9:26 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-12 7:10 [PATCH v2 0/4] mm/hugetlb: fixes for PMD table sharing (incl. using mmu_gather) David Hildenbrand (Red Hat)
2025-12-12 7:10 ` [PATCH v2 1/4] mm/hugetlb: fix hugetlb_pmd_shared() David Hildenbrand (Red Hat)
2025-12-12 7:10 ` [PATCH v2 2/4] mm/hugetlb: fix two comments related to huge_pmd_unshare() David Hildenbrand (Red Hat)
2025-12-19 4:44 ` Harry Yoo
2025-12-19 6:11 ` David Hildenbrand (Red Hat)
2025-12-19 11:20 ` Harry Yoo
2025-12-19 14:13 ` David Hildenbrand (Red Hat)
2025-12-19 21:37 ` Nadav Amit
2025-12-21 9:26 ` David Hildenbrand (Red Hat) [this message]
2025-12-12 7:10 ` [PATCH v2 3/4] mm/rmap: " David Hildenbrand (Red Hat)
2025-12-12 7:10 ` [PATCH v2 4/4] mm/hugetlb: fix excessive IPI broadcasts when unsharing PMD tables using mmu_gather David Hildenbrand (Red Hat)
2025-12-16 10:47 ` Lorenzo Stoakes
2025-12-19 12:37 ` Harry Yoo
2025-12-19 13:52 ` David Hildenbrand (Red Hat)
2025-12-19 13:59 ` David Hildenbrand (Red Hat)
2025-12-21 12:24 ` David Hildenbrand (Red Hat)
2025-12-22 2:09 ` Harry Yoo
2025-12-22 10:10 ` David Hildenbrand (Red Hat)
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