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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id c1-20020a05622a024100b0039cc0fbdb61sm10856656qtx.53.2022.11.09.18.10.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Nov 2022 18:10:14 -0800 (PST) Date: Wed, 9 Nov 2022 18:10:12 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Sidhartha Kumar cc: Hugh Dickins , Andrew Morton , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Vlastimil Babka , Peter Xu , Yang Shi , John Hubbard , Mike Kravetz , Muchun Song , Miaohe Lin , Naoya Horiguchi , Mina Almasry , James Houghton , Zach O'Keefe , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/3] mm,hugetlb: use folio fields in second tail page In-Reply-To: Message-ID: <7f60bcac-a2e5-9c4b-8a8f-e972a93e116@google.com> References: <5f52de70-975-e94f-f141-543765736181@google.com> <3818cc9a-9999-d064-d778-9c94c5911e6@google.com> <5bd8a365-e2c5-a721-1257-81ec4ae0c626@oracle.com> <3934b34-ae2f-2119-9a68-33e51e909795@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Nov 2022, Sidhartha Kumar wrote: > On 11/3/22 9:29 PM, Hugh Dickins wrote: > > > >> Should the usage of page_1 and page_2 also be documented here? > > You must have something interesting in mind to document about them, > > but I cannot guess what! They are for field alignment, not for use. > > (page_2 to help when/if someone needs to add another pageful.) > > > > Do you mean that I should copy the > > /* private: the union with struct page is transitional */ > > comment from above the original "struct page page;" line I copied? > > Or give all three of them a few underscores to imply not for use? > > I think the underscores with a comment about not for use could be helpful. I've given them two underscores (but not to the original "struct page page", since a build showed that used as "page" elsewhere, not just for alignment). I'm sorry, but I've not given them any comment: I don't think they belong in the commented fields section (_flags_1 etc), "page" is not there; and I'm, let's be honest, terrified of dabbling in this kerneldoc area - feel very fortunate to have escaped attack by a robot for my additions so far. I'll leave adding comment to you or other cognoscenti. Hugh