From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 12026C433F5 for ; Tue, 8 Mar 2022 21:46:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 652958D0002; Tue, 8 Mar 2022 16:46:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 601508D0001; Tue, 8 Mar 2022 16:46:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4C9A08D0002; Tue, 8 Mar 2022 16:46:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0094.hostedemail.com [216.40.44.94]) by kanga.kvack.org (Postfix) with ESMTP id 3CB548D0001 for ; Tue, 8 Mar 2022 16:46:21 -0500 (EST) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id DFB891828AC85 for ; Tue, 8 Mar 2022 21:46:20 +0000 (UTC) X-FDA: 79222552920.25.D1329E2 Received: from mail-qk1-f182.google.com (mail-qk1-f182.google.com [209.85.222.182]) by imf19.hostedemail.com (Postfix) with ESMTP id 8694E1A0010 for ; Tue, 8 Mar 2022 21:46:20 +0000 (UTC) Received: by mail-qk1-f182.google.com with SMTP id h196so220122qke.12 for ; Tue, 08 Mar 2022 13:46:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:in-reply-to:message-id:references :mime-version; bh=pBT9wHk0kv9phQaF2jSMAucWeXRUjsHTpKabj8I6JEU=; b=RAmhDr5MJvaQL3qZE74+KSH75ORbbrkgRY9YObb//xmoMlf33p1hpBU9rIXZG6L7ml J+/UM1uySARXqyiozkXgec1tI0uVeDVycFFmvGBE54shXKr2/rvIjivnr7QpM+2k1g+X +MyLRsKUEWJsrs8IpmNwBg0pBdBBlc0pA0nJUj7Thmh2J9Fz9sOANtG3znbE95Dm8lrO HCzlO5HMdIBw9+kLBiRDV0nqPh+7o9hbPBoNbAXXXds8jWdu1YLtB7e8jax1fkkbp7iR cjg2PIbda0n5tQiHwcjQQwDU8eQ4Bw5JM4SDtvvqYk7/xwSqid8QSIaayOx11CfWeNOO hPJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:mime-version; bh=pBT9wHk0kv9phQaF2jSMAucWeXRUjsHTpKabj8I6JEU=; b=eUqIGdb8uIbkeo9koBoN4CrxZf+x6qkudbUwVK5hIhc/dsFHfQqpvDayJhObnoFgZw fp4mXaZZJT4mYCj1hWWEDpHyJWoYV386O06sBGkPv/eLOFuE9aEUKgPUfCqVVAynWik+ kama34qCYf+dpj3alaSaSF0pvzhdyu/169TFPbescQw/LNW0sz+qPNnsEQqI5qiQYFkl ql48TIwrGJVcTsjNmbCi5Q+LRwKc+Ylz9sVuOrrI+YojAlBg4paDRkELuE+8Mgs0Zlzk 3xhIuTeOmztqHGjuiFwsxw34F3yflXFSohpeisSJs5qw09A3Mc/Q+HvGfICvkKjc0jTP /oLg== X-Gm-Message-State: AOAM533KPcaCVefaEIwPG7i9mbULUbIjHh06I6c+F64GJpmsZMyZZ/t2 7RCkYGByD5BUyCRH/QNAekYmlw== X-Google-Smtp-Source: ABdhPJxWHyEAuF8GKQrPH4aj80OVaMZ68Mo/l/yema1f/6PqDgdd6gWKrf8+d4sG3STa70ORNpDdgg== X-Received: by 2002:a05:620a:134e:b0:67b:d16:89f7 with SMTP id c14-20020a05620a134e00b0067b0d1689f7mr9931286qkl.123.1646775979553; Tue, 08 Mar 2022 13:46:19 -0800 (PST) Received: from ripple.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id g2-20020a37e202000000b00607e264a208sm66421qki.40.2022.03.08.13.46.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Mar 2022 13:46:19 -0800 (PST) Date: Tue, 8 Mar 2022 13:46:15 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@ripple.anvils To: "Darrick J. Wong" cc: Christoph Hellwig , Hugh Dickins , Andrew Morton , Mikulas Patocka , Zdenek Kabelac , Lukas Czerner , Miklos Szeredi , Borislav Petkov , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH mmotm v2] tmpfs: do not allocate pages on read In-Reply-To: <20220308172734.GC1479066@magnolia> Message-ID: <9798e3b-1c2a-6c47-decc-7d4148de5114@google.com> References: <20220306092709.GA22883@lst.de> <90bc5e69-9984-b5fa-a685-be55f2b64b@google.com> <20220307064434.GA31680@lst.de> <20220308172734.GC1479066@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8694E1A0010 X-Rspam-User: Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=RAmhDr5M; spf=pass (imf19.hostedemail.com: domain of hughd@google.com designates 209.85.222.182 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: gxb8shfc8ao1ycxoq63gjqagwrk6my73 X-HE-Tag: 1646775980-901089 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 Tue, 8 Mar 2022, Darrick J. Wong wrote: > > I've long wondered (for my own nefarious purposes) why tmpfs files > didn't just grab the zero page, (tmpfs files have been using the zero page for reads for many years: it was just this odd internal "could it be for a stacking filesystem?" case, which /dev/loop also fell into, which was doing allocation on read. I wonder what your nefarious purposes are ;) Maybe related to pages faulted into an mmap: those pages tmpfs has always allocated for, then they're freed up later by page reclaim if still undirtied. We may change that in future, and use the zero page even there: there are advantages of course, but some care and code needed - never been a priority.) > so: > > Acked-by: Darrick J. Wong Thanks, Hugh