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Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Rik van Riel , Harry Yoo , Laurence Oberman , Prakash Sangappa , Nadav Amit , Liu Shixin Subject: [PATCH v3 2/3] mm/rmap: fix two comments related to huge_pmd_unshare() Date: Tue, 23 Dec 2025 21:50:45 +0100 Message-ID: <20251223205046.565162-3-david@kernel.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251223205046.565162-1-david@kernel.org> References: <20251223205046.565162-1-david@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: A546E40004 X-Rspamd-Server: rspam04 X-Stat-Signature: 9f71bfafu3y4gijsxn4xuxz6inodfruf X-HE-Tag: 1766523068-729672 X-HE-Meta: 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 0Svgo9Mb BOU59GeblRE36S5Rn7sclZQ2VBsH154tqu7/xw1ao5VwoIXEmDQ3K9Tc0hWRd6FbrvvoHtge+9yPmKvw4PNGOdLgANlckgVeiudncdae7FxyxhAli0aBCYSIEEgA2E99K1nvKbdr6eDu/qSRCf5NLd3WyMQwQ6IzyTQOKwHPGR8SqDjtIgceXSrMpF0em4rO1oTzg6+nrzXaO25WjhGTGoQ0cNs4Vi3ZGc4hP2971loHTagqNdrxgb5hINJh18YKpiGhYLUtO2CKph16T2lDkqPKTuBPQBoLpN7eu/LhUDDfKoL/4WaA3D9sv7K49Mjw7VIrPqBF7LsJ23vcYubRi+MtwkfOrv72srnnLFr2zFsmRNKfCQkLkwGar3oK5QusF7pGyRvpbWaVxUxsuGxEgVovgdoAtpsif6jkXyGdLbutNbG65ixkVKg3iSJd9DXkxxepfQjatwLmnr9wKNTvvjWTIj911nkf7EVX4 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: PMD page table unsharing no longer touches the refcount of a PMD page table. Also, it is not about dropping the refcount of a "PMD page" but the "PMD page table". Let's just simplify by saying that the PMD page table was unmapped, consequently also unmapping the folio that was mapped into this page. This code should be deduplicated in the future. Fixes: 59d9094df3d7 ("mm: hugetlb: independent PMD page table shared count") Reviewed-by: Rik van Riel Tested-by: Laurence Oberman Reviewed-by: Lorenzo Stoakes Acked-by: Oscar Salvador Cc: Liu Shixin Signed-off-by: David Hildenbrand (Red Hat) --- mm/rmap.c | 20 ++++---------------- 1 file changed, 4 insertions(+), 16 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index f955f02d570ed..748f48727a162 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2016,14 +2016,8 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, flush_tlb_range(vma, range.start, range.end); /* - * The ref count of the PMD page was - * dropped which is part of the way map - * counting is done for shared PMDs. - * Return 'true' here. When there is - * no other sharing, huge_pmd_unshare - * returns false and we will unmap the - * actual page and drop map count - * to zero. + * The PMD table was unmapped, + * consequently unmapping the folio. */ goto walk_done; } @@ -2416,14 +2410,8 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, range.start, range.end); /* - * The ref count of the PMD page was - * dropped which is part of the way map - * counting is done for shared PMDs. - * Return 'true' here. When there is - * no other sharing, huge_pmd_unshare - * returns false and we will unmap the - * actual page and drop map count - * to zero. + * The PMD table was unmapped, + * consequently unmapping the folio. */ page_vma_mapped_walk_done(&pvmw); break; -- 2.52.0