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Thu, 11 Dec 2025 05:41:11 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id cnNVMXdZOmnRMQAAD6G6ig (envelope-from ); Thu, 11 Dec 2025 05:41:11 +0000 Date: Thu, 11 Dec 2025 06:41:10 +0100 From: Oscar Salvador To: "David Hildenbrand (Red Hat)" Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, Will Deacon , "Aneesh Kumar K.V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Arnd Bergmann , Muchun Song , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Rik van Riel , Harry Yoo , Laurence Oberman , Prakash Sangappa , Nadav Amit , Liu Shixin Subject: Re: [PATCH v1 2/4] mm/hugetlb: fix two comments related to huge_pmd_unshare() Message-ID: References: <20251205213558.2980480-1-david@kernel.org> <20251205213558.2980480-3-david@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251205213558.2980480-3-david@kernel.org> X-Rspamd-Action: no action X-Stat-Signature: 4peir4cx3q3w4ax4sqqeafbge8hbngpw X-Rspam-User: X-Rspamd-Queue-Id: BD455C0008 X-Rspamd-Server: rspam01 X-HE-Tag: 1765431675-183519 X-HE-Meta: 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 6Pzv4z7F RurzwR7z59cOrO1VEO3LE/AOamKpOReVGgHG8YztNrZx3FvWvj+uqCCk10idP22oykXKBCr7DfMkfRCu19jzW7CfktUZPpsp9VtwJePzN+FxrgRE+4vXu9/j/2YXdEjmrzxeLgVHAjam8f8v1XicDVvkAYO4WrLQLTW3Tr0FY3t7XlCYUpkLXZcb17hVusQg1gTj5ddsd5DjuC7dSVIqd1qQd4rJy8sK8iFgl7UEjW+9xM2bd+M9Z2SV9PcNt2UwKHbPZdxn1mQmBqqo0d45NaeUxFuyOhaY4K6aY+XgAH2mgIbt/+Oz65fctebd/SgbpLXBKCVbXXPL6TbxloaDI9s1hS9HiCGZp2Pw7IKkpV9Gw6kaHn3i7IvnQdicSjVWE4tTlD08wEQjbIApNjt6Kn2dEf0c77H1dMYapQ06c8q0hqtHaqlRy9DixYA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Dec 05, 2025 at 10:35:56PM +0100, David Hildenbrand (Red Hat) wrote: > Ever since we stopped using the page count to detect shared PMD > page tables, these comments are outdated. > > The only reason we have to flush the TLB early is because once we drop > the i_mmap_rwsem, the previously shared page table could get freed (to > then get reallocated and used for other purpose). So we really have to > flush the TLB before that could happen. > > So let's simplify the comments a bit. > > The "If we unshared PMDs, the TLB flush was not recorded in mmu_gather." > part introduced as in commit a4a118f2eead ("hugetlbfs: flush TLBs > correctly after huge_pmd_unshare") was confusing: sure it is recorded > in the mmu_gather, otherwise tlb_flush_mmu_tlbonly() wouldn't do > anything. So let's drop that comment while at it as well. > > We'll centralize these comments in a single helper as we rework the code > next. > > Fixes: 59d9094df3d7 ("mm: hugetlb: independent PMD page table shared count") > Cc: Liu Shixin > Signed-off-by: David Hildenbrand (Red Hat) Acked-by: Oscar Salvador -- Oscar Salvador SUSE Labs