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[209.85.167.44]) by smtp.gmail.com with ESMTPSA id q25sm1405775lfd.282.2020.12.19.12.08.37 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 19 Dec 2020 12:08:38 -0800 (PST) Received: by mail-lf1-f44.google.com with SMTP id o19so14350985lfo.1 for ; Sat, 19 Dec 2020 12:08:37 -0800 (PST) X-Received: by 2002:ac2:4987:: with SMTP id f7mr3561966lfl.41.1608408517290; Sat, 19 Dec 2020 12:08:37 -0800 (PST) MIME-Version: 1.0 References: <20201210150828.4b7pg5lx666r7l2u@black.fi.intel.com> <20201214160724.ewhjqoi32chheone@box> <20201216170703.o5lpsnjfmoj7f3ml@box> <20201217105409.2gacwgg7rco2ft3m@box> <20201218110400.yve45r3zsv7qgfa3@box> <20201219124103.w6isern3ywc7xbur@box> In-Reply-To: <20201219124103.w6isern3ywc7xbur@box> From: Linus Torvalds Date: Sat, 19 Dec 2020 12:08:21 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting To: "Kirill A. Shutemov" Cc: Matthew Wilcox , "Kirill A. Shutemov" , Will Deacon , Linux Kernel Mailing List , Linux-MM , Linux ARM , Catalin Marinas , Jan Kara , Minchan Kim , Andrew Morton , Vinayak Menon , Android Kernel Team Content-Type: text/plain; charset="UTF-8" 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: On Sat, Dec 19, 2020 at 4:41 AM Kirill A. Shutemov wrote: > > Okay, but we only win the NULL check. xas_retry() and xa_is_value() has to > be repeated in the beginning of the loop. Yeah. I wonder if it might make sense to have a "xas_next_entry_rcu()" function that does something like while ((entry = xas_next_entry(&xas, end)) != NULL) { if (xas_retry(entry) || xa_is_value(entry)) continue; return entry; } return NULL; but that's a question for Willy, and independent of this patch. I like the patch, and I'll think about it a bit more, but I might decide to just apply it to get this thing over with. Otherwise it should probably go into -mm for more testing. Linus