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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id r129-20020acac187000000b002ef358c6e0esm5643602oif.49.2022.04.05.12.59.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Apr 2022 12:59:51 -0700 (PDT) Date: Tue, 5 Apr 2022 12:59:41 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.anvils To: Patrice CHOTARD cc: hughd@google.com, mpatocka@redhat.com, lczerner@redhat.com, djwong@kernel.org, hch@lst.de, zkabelac@redhat.com, miklos@szeredi.hu, bp@suse.de, akpm@linux-foundation.org, Alexandre TORGUE - foss , Valentin CARON - foss , linux-stm32@st-md-mailman.stormreply.com, Linux Kernel Mailing List , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: Regression with v5.18-rc1 tag on STM32F7 and STM32H7 based boards In-Reply-To: <481a13f8-d339-f726-0418-ab4258228e91@foss.st.com> Message-ID: <95a0d1dd-bcce-76c7-97b9-8374c9913321@google.com> References: <481a13f8-d339-f726-0418-ab4258228e91@foss.st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Stat-Signature: skbaj5mguda9r8ccu9hgh5mocqeutg4c Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b="Rkj/0lao"; spf=pass (imf03.hostedemail.com: domain of hughd@google.com designates 209.85.210.42 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: DDCDD20019 X-HE-Tag: 1649188794-732185 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, 5 Apr 2022, Patrice CHOTARD wrote: > > We found an issue with last kernel tag v5.18-rc1 on stm32f746-disco and > stm32h743-disco boards (ARMV7-M SoCs). > > Kernel hangs when executing SetPageUptodate(ZERO_PAGE(0)); in mm/filemap.c. > > By reverting commit 56a8c8eb1eaf ("tmpfs: do not allocate pages on read"), > kernel boots without any issue. Sorry about that, thanks a lot for finding. I see that arch/arm/configs/stm32_defconfig says CONFIG_MMU is not set: please confirm that is the case here. Yes, it looks as if NOMMU platforms are liable to have a bogus (that's my reading, but it may be unfair) definition for ZERO_PAGE(vaddr), and I was walking on ice to touch it without regard for !CONFIG_MMU. CONFIG_SHMEM depends on CONFIG_MMU, so that PageUptodate is only needed when CONFIG_MMU. Easily fixed by an #ifdef CONFIG_MMU there in mm/filemap.c, but I'll hunt around (again) for a better place to do it - though I won't want to touch all the architectures for it. I'll post later today. Hugh