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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6D51BCCD194 for ; Thu, 16 Oct 2025 10:22:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C20B58E0017; Thu, 16 Oct 2025 06:22:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BF8E28E000B; Thu, 16 Oct 2025 06:22:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B0E418E0017; Thu, 16 Oct 2025 06:22:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 9E2DD8E000B for ; Thu, 16 Oct 2025 06:22:07 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 69842C026F for ; Thu, 16 Oct 2025 10:22:07 +0000 (UTC) X-FDA: 84003587094.05.DE6BD56 Received: from fhigh-a6-smtp.messagingengine.com (fhigh-a6-smtp.messagingengine.com [103.168.172.157]) by imf15.hostedemail.com (Postfix) with ESMTP id 1B564A000F for ; Thu, 16 Oct 2025 10:22:04 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm1 header.b="V 0H7RB8"; dkim=pass header.d=messagingengine.com header.s=fm2 header.b=P2jcDerb; dmarc=none; spf=pass (imf15.hostedemail.com: domain of kirill@shutemov.name designates 103.168.172.157 as permitted sender) smtp.mailfrom=kirill@shutemov.name ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1760610125; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4cgizSnh8FyjftsIcMN/5doeb/L5sYJZzPBngz1cPTs=; b=4QlxSYWBwJYYeA6NGHRXwlD60Mq4jA+4ARqfHvDfPU4JY3qpE6aqsf4SWiy+6fYR6rDVHG APuN8VqryeZJzkqj+HwU4Zszvj4E1EwLGcUP+JgolahFmEO7gJ5NEQdj9yACkn1VgtlanL zhDXb/F/CcFv/PdH2p3hxSvAsGMB8tg= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1760610125; a=rsa-sha256; cv=none; b=WTAAX4CYyt0ZsIUpnF8QwGA4KFRZDfKA3rFJbFYdlpPfy9YDqvldNo+XPK5F29Olx3hgz9 FelK8pDJI8Ja9iy+no6UsohWfTDzs3BMeBFnZdlvoKwosq/YhR10EBHZhWk17oyLNiBrL9 fj9km3yRdo82J7IJNHNIk1o/W3hyWjg= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm1 header.b="V 0H7RB8"; dkim=pass header.d=messagingengine.com header.s=fm2 header.b=P2jcDerb; dmarc=none; spf=pass (imf15.hostedemail.com: domain of kirill@shutemov.name designates 103.168.172.157 as permitted sender) smtp.mailfrom=kirill@shutemov.name Received: from phl-compute-05.internal (phl-compute-05.internal [10.202.2.45]) by mailfhigh.phl.internal (Postfix) with ESMTP id 608701400208; Thu, 16 Oct 2025 06:22:04 -0400 (EDT) Received: from phl-mailfrontend-02 ([10.202.2.163]) by phl-compute-05.internal (MEProxy); Thu, 16 Oct 2025 06:22:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov.name; h=cc:cc:content-type:content-type:date:date:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:subject:subject:to:to; s=fm1; t=1760610124; x= 1760696524; bh=4cgizSnh8FyjftsIcMN/5doeb/L5sYJZzPBngz1cPTs=; b=V 0H7RB8kX6dTe4pJfkGYa84CFGKQi7NQQwlIG5JtdXa17rPgjGU7VP1Im0x2JCx0C erNolu6GR6GrwirzS9l8PkU+m7UIbkA7XvpPXC7ZFyxsPYDEIbw1RrFzpxGqkE0I XSX2c5KYOu4R22qernV1tzWejdNPVpiF6l4acfHqHponV+OQwKMyBJBac6s3srED hFX3UEvTtKGF2/OHDDBf5m2oNLPo9+mcCfSWNi51R4gTtStNacgN9I+rh/zOeCdI bzeQI6SB+IMUgCVz7V3V15HPW5Ew/NXITdHFdAV6G//4gfIEajOAOqA9Yzk/TrTw tQ6ZnYipFhCaAm0qTeNoQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:subject:subject:to :to:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; t= 1760610124; x=1760696524; bh=4cgizSnh8FyjftsIcMN/5doeb/L5sYJZzPB ngz1cPTs=; b=P2jcDerbD5gusICBdwO0U719/hGR3gBgsrnEyk/uej3H9tIAQJG v7VgnltT3EvGvGG8+qrHW8D01JayYRv3okQbhAmUsijIbYrDIUKZ6S3S5/B9uLUr sSSx+QliS0zx1jH0Gxkvh7EyhpBHhERXy7acCWQLVRCPtOoRUXrp0MEcdkW7nZjF p/YgXjCydO23+cAAi/nmtPR0J1TjbTgQCUbErZT3E3/AZQlhYg8dzAaolvdkjNEN dC7i/NUPFe6YIqVV+eM8q9ZRv9QGFDBjT52AcCsxFfamN6djOIogNSb9V9SX4oeH phBvOoSe7RTOsP15zKrE1xGb5EaNosPQYkw== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtdeggdduvdeitdegucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfurfetoffkrfgpnffqhgenuceu rghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujf gurhepfffhvfevuffkfhggtggujgesthdtsfdttddtvdenucfhrhhomhepmfhirhihlhcu ufhhuhhtshgvmhgruhcuoehkihhrihhllhesshhhuhhtvghmohhvrdhnrghmvgeqnecugg ftrfgrthhtvghrnhepjeehueefuddvgfejkeeivdejvdegjefgfeeiteevfffhtddvtdel udfhfeefffdunecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrh homhepkhhirhhilhhlsehshhhuthgvmhhovhdrnhgrmhgvpdhnsggprhgtphhtthhopedu kedpmhhouggvpehsmhhtphhouhhtpdhrtghpthhtohepughjfihonhhgsehkvghrnhgvlh drohhrghdprhgtphhtthhopeifihhllhihsehinhhfrhgruggvrggurdhorhhgpdhrtghp thhtohepmhgtghhrohhfsehkvghrnhgvlhdrohhrghdprhgtphhtthhopehprdhrrghghh grvhesshgrmhhsuhhnghdrtghomhdprhgtphhtthhopeiilhgrnhhgsehrvgguhhgrthdr tghomhdprhgtphhtthhopegrkhhpmheslhhinhhugidqfhhouhhnuggrthhiohhnrdhorh hgpdhrtghpthhtoheplhhinhhugidqmhhmsehkvhgrtghkrdhorhhgpdhrtghpthhtohep lhhinhhugidqfhhsuggvvhgvlhesvhhgvghrrdhkvghrnhgvlhdrohhrghdprhgtphhtth hopehlihhnuhigqdigfhhssehvghgvrhdrkhgvrhhnvghlrdhorhhg X-ME-Proxy: Feedback-ID: ie3994620:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Thu, 16 Oct 2025 06:22:02 -0400 (EDT) Date: Thu, 16 Oct 2025 11:22:00 +0100 From: Kiryl Shutsemau To: "Darrick J. Wong" , Matthew Wilcox , Luis Chamberlain , Pankaj Raghav , Zorro Lang Cc: akpm@linux-foundation.org, linux-mm , linux-fsdevel , xfs Subject: Re: Regression in generic/749 with 8k fsblock size on 6.18-rc1 Message-ID: References: <20251014175214.GW6188@frogsfrogsfrogs> <20251015175726.GC6188@frogsfrogsfrogs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251015175726.GC6188@frogsfrogsfrogs> X-Rspamd-Server: rspam01 X-Stat-Signature: wkuya6jc8hqrds6b38jz4rt3j5jctwx3 X-Rspam-User: X-Rspamd-Queue-Id: 1B564A000F X-HE-Tag: 1760610124-923682 X-HE-Meta: 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 0BlCNMuu ytHyDXW41rsLK+Dk9LANwwiRBwdYtSAoZDCPxulgQRHqpGeu9vU69Wtfb71nl41uwpCkpeso0MwheVSlTIUOf6j8BlxRtuBBxE6sYsYaoBIkn4Qvx5kvTebMj+Nq0cJK8VKwbjx9kvthsBk+pBuA1tU03oeo/d+qOYfdRvQ3gn7C5kM4E/OC4123VhknGWiOEK5FmCabIWOPhV8Rhu0DXsSwHnuYP8BrFYlyVIm4+SiKkXlXV7HoD9n73OQzVKwC3AWZGFd4aq/bXNj66SHE27zQDwMs1S72fSqOVm2DwSBu8u9v+WL6WquzsQ+WzP3ErveBkgbzdTDtfgoP5XzkoMsMp+whKIdudJSWgsYJaOM/0Vn2v/o/0y8RLthPeVR4BX8Oe+SPS09H+MJjPjYZU4hxxgg== 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: List-Subscribe: List-Unsubscribe: On Wed, Oct 15, 2025 at 10:57:26AM -0700, Darrick J. Wong wrote: > On Wed, Oct 15, 2025 at 04:59:03PM +0100, Kiryl Shutsemau wrote: > > On Tue, Oct 14, 2025 at 10:52:14AM -0700, Darrick J. Wong wrote: > > > Hi there, > > > > > > On 6.18-rc1, generic/749[1] running on XFS with an 8k fsblock size fails > > > with the following: > > > > > > --- /run/fstests/bin/tests/generic/749.out 2025-07-15 14:45:15.170416031 -0700 > > > +++ /var/tmp/fstests/generic/749.out.bad 2025-10-13 17:48:53.079872054 -0700 > > > @@ -1,2 +1,10 @@ > > > QA output created by 749 > > > +Expected SIGBUS when mmap() reading beyond page boundary > > > +Expected SIGBUS when mmap() writing beyond page boundary > > > +Expected SIGBUS when mmap() reading beyond page boundary > > > +Expected SIGBUS when mmap() writing beyond page boundary > > > +Expected SIGBUS when mmap() reading beyond page boundary > > > +Expected SIGBUS when mmap() writing beyond page boundary > > > +Expected SIGBUS when mmap() reading beyond page boundary > > > +Expected SIGBUS when mmap() writing beyond page boundary > > > Silence is golden > > > > > > This test creates small files of various sizes, maps the EOF block, and > > > checks that you can read and write to the mmap'd page up to (but not > > > beyond) the next page boundary. > > > > > > For 8k fsblock filesystems on x86, the pagecache creates a single 8k > > > folio to cache the entire fsblock containing EOF. If EOF is in the > > > first 4096 bytes of that 8k fsblock, then it should be possible to do a > > > mmap read/write of the first 4k, but not the second 4k. Memory accesses > > > to the second 4096 bytes should produce a SIGBUS. > > > > Does anybody actually relies on this behaviour (beyond xfstests)? > > Beats me, but the mmap manpage says: ... > POSIX 2024 says: ... > From both I would surmise that it's a reasonable expectation that you > can't map basepages beyond EOF and have page faults on those pages > succeed. Modern kernel with large folios blurs the line of what is the page. I don't want play spec lawyer. Let's look at real workloads. If there's anything that actually relies on this SIGBUS corner case, let's see how we can fix the kernel. But it will cost some CPU cycles. If it only broke syntactic test case, I'm inclined to say WONTFIX. Any opinions? -- Kiryl Shutsemau / Kirill A. Shutemov