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Shutemov" , David Hildenbrand , Yang Shi , Miaohe Lin , Kefeng Wang , Yu Zhao , John Hubbard , Baolin Wang , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Kairui Song Subject: Re: [PATCH v10 2/8] mm/huge_memory: add two new (not yet used) functions for folio_split() Message-ID: References: <20250307174001.242794-1-ziy@nvidia.com> <20250307174001.242794-3-ziy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: oa3sxadtf49qeubj3qgda9zwyi89byu3 X-Rspam-User: X-Rspamd-Queue-Id: D0B3F100038 X-Rspamd-Server: rspam01 X-HE-Tag: 1741626050-120914 X-HE-Meta: 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 vIQGHe3L Jp97wXhBM4O/WaBAqC/9Ht9C9PG85H6A7/4fecHx3BvEbnVewFG+HlQO/We2DNPXKbzqsLMqHDq66+x5a10odGh+ydlKLaZQYfHSt5AuFZg017qLm4bmBivRnFhh4s5ULMgJYbSC8VMKNF78mI1BWyVliJusyxJnszFqv680HHIIKxt7P2//xZ1DQttGEIC/mU4D6iEMCLJNosCB9XQggXQ5Gb0z8UiTkzmLOrasPMlgfL+G/qcqyglthrujhktxgKBdZ/QtGNlDBJ1Wvq5Fy7hit308kccaTBTsu9KIo0HRkqT4= 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 Mon, Mar 10, 2025 at 12:42:06PM -0400, Zi Yan wrote: > > Because of the “Careful” comment. But new_folio->* should be fine, > > since it is the same as new_head. So I probably can replace all > > new_head with new_folio except those VM_BUG_ON_PAGE checks? Why not also the VM_BUG_ON_PAGE check? I mean: > @@ -3364,8 +3364,8 @@ static void __split_folio_to_order(struct folio *folio, int old_order, > /* ->mapping in first and second tail page is replaced by other uses */ > VM_BUG_ON_PAGE(new_nr_pages > 2 && new_head->mapping != TAIL_MAPPING, > new_head); VM_BUG_ON_PAGE(new_nr_pages > 2 && new_folio->mapping != TAIL_MAPPING, new_head); (or we could just ditch the assert entirely; it's not all that useful) > - new_head->mapping = head->mapping; > - new_head->index = head->index + index; > + new_folio->mapping = head->mapping; > + new_folio->index = head->index + index; new_folio->mapping = folio->mapping new_folio->index = folio->index +index; (um, and that index + index looks weird; better name might be just 'i')