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dkim=none (message not signed) header.d=none;kvack.org; dmarc=none action=none header.from=oracle.com; Received: from BYAPR10MB3077.namprd10.prod.outlook.com (2603:10b6:a03:8c::12) by BY5PR10MB3763.namprd10.prod.outlook.com (2603:10b6:a03:1f5::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.17; Thu, 4 Feb 2021 11:48:04 +0000 Received: from BYAPR10MB3077.namprd10.prod.outlook.com ([fe80::74a8:8649:e20b:d571]) by BYAPR10MB3077.namprd10.prod.outlook.com ([fe80::74a8:8649:e20b:d571%7]) with mapi id 15.20.3805.024; Thu, 4 Feb 2021 11:47:57 +0000 Subject: Re: [PATCH 3/4] mm/gup: add a range variant of unpin_user_pages_dirty_lock() To: John Hubbard Cc: linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Andrew Morton , Jason Gunthorpe , Doug Ledford , Matthew Wilcox , linux-mm@kvack.org References: <20210203220025.8568-1-joao.m.martins@oracle.com> <20210203220025.8568-4-joao.m.martins@oracle.com> From: Joao Martins Message-ID: <9e70bd93-783f-3d0d-c53f-ec32480477d6@oracle.com> Date: Thu, 4 Feb 2021 11:47:51 +0000 In-Reply-To: Content-Type: text/plain; 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>> + struct page *head; >> + unsigned int ntails; >> + >> + for_each_compound_range(index, &page, npages, head, ntails) { >> + if (make_dirty && !PageDirty(head)) >> + set_page_dirty_lock(head); >> + put_compound_head(head, ntails, FOLL_PIN); >> + } >> +} >> +EXPORT_SYMBOL(unpin_user_page_range_dirty_lock); >> + > > Also, looking at this again while trying to verify the sg diffs in patch #4, I noticed > that the name is tricky. Usually a "range" would not have a single struct page* as the > argument. So in this case, perhaps a comment above the function would help, something > approximately like this: > > /* > * The "range" in the function name refers to the fact that the page may be a > * compound page. If so, then that compound page will be treated as one or more > * ranges of contiguous tail pages. > */ > > ...I guess. Or maybe the name is just wrong (a comment block explaining a name is > always a bad sign). Naming aside, a comment is probably worth nonetheless to explain what the function does. > Perhaps we should rename it to something like: > > unpin_user_compound_page_dirty_lock() > > ? The thing though, is that it doesn't *only* unpin a compound page. It unpins a contiguous range of pages (hence page_range) *and* if these are compound pages it further accelerates things. Albeit, your name suggestion then probably hints the caller that you should be passing a compound page anyways, so your suggestion does have a ring to it. Joao