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 2B24BC25B75 for ; Tue, 4 Jun 2024 00:35:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 96CB46B0083; Mon, 3 Jun 2024 20:34:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 91BC26B0085; Mon, 3 Jun 2024 20:34:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7BC896B0088; Mon, 3 Jun 2024 20:34:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 5D8E56B0083 for ; Mon, 3 Jun 2024 20:34:59 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id DE5811205D4 for ; 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imf03.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf03.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1717461297; a=rsa-sha256; cv=none; b=LkiC/gE68ZiyYa50VWLMbXThv4RKZnUCTh/o+GfjqtQUqnAPiZmt0Uy7VGxm856SXkWKRa XWXwMb+kDOq4Of/CqXOtJWRE+QfkHgdBrHGf1L6NAtwjs6TyUtW20n1JupebYu/xbRLv1R kuPjfdIZUaTSvUWMo3+rgvRDTO4/4UY= X-AuditID: a67dfc5b-d6dff70000001748-ca-665e612dbd5d Date: Tue, 4 Jun 2024 09:34:48 +0900 From: Byungchul Park To: Matthew Wilcox Cc: Dave Hansen , David Hildenbrand , Byungchul Park , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org, ying.huang@intel.com, vernhao@tencent.com, mgorman@techsingularity.net, hughd@google.com, peterz@infradead.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, rjgolo@gmail.com Subject: Re: [PATCH v11 09/12] mm: implement LUF(Lazy Unmap Flush) defering tlb flush when folios get unmapped Message-ID: <20240604003448.GA26609@system.software.com> References: <20240531092001.30428-10-byungchul@sk.com> <26dc4594-430b-483c-a26c-7e68bade74b0@redhat.com> <20240603093505.GA12549@system.software.com> <35866f91-7d96-462a-aa0a-ac8a6b8cbcf8@redhat.com> <196481bb-b86d-4959-b69b-21fda4daae77@intel.com> MIME-Version: 1.0 Content-Type: text/plain; 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We've got something like 1000 currently > unused values which can't be mistaken for anything else. > > > That would actually have a chance at fixing two issues: One where a new > > page cache insertion is attempted. The other where someone goes to look > > in the page cache and takes some action _because_ it is empty (I think > > NFS is doing some of this for file locks). > > > > LUF is also pretty fundamentally built on the idea that files can't > > change without LUF being aware. That model seems to work decently for > > normal old filesystems on normal old local block devices. I'm worried > > about NFS, and I don't know how seriously folks take FUSE, but it > > obviously can't work well for FUSE. > > I'm more concerned with: > > - page goes back to buddy > - page is allocated to slab At this point, tlb flush needed will be performed in prep_new_page(). > - application reads through stale TLB entry and sees kernel memory No worry for this case. Byungchul > > Or did that scenario get resolved?