From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE021609A73A for ; Mon, 2 Nov 2026 15:26:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=aDk6OKCI Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4jJFsg4fL9z3dWJ; Tue, 03 Nov 2026 02:26:15 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=172.234.252.31 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1793633175; cv=none; b=J1Wu/u2UZU1LnsLFKMjCo8ghQhsBeNgqZdhC4ggk60d5v51AjAEJ4kZsv31BdM5x7WQNXHXoi1OBrC3YKgqgbwwFg1qISb/qKDilcxsrfi5yWKh9aGNqlz+TRnO8guRYHODo+tP6+etgzE9utYBYRjvPt6bRUdop8q7CF8hbvjamSQqDnCzoTfYtuc92XWiA+RuyaumL7kCJACLlusIfLeqrjiSkRaAqScW6uZXNR2lThpzqCE8qy3LT6asEbdJQj2WdNUlhX7addXa5CJmxFFZndALhXRo1+CSPUiWQb0EeUa+nVw1qQkc7cj/4mQ06w+7Mq7TZrkD9zxCUf2qvpg== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1793633175; c=relaxed/relaxed; bh=B1LcgTjI6osh59ZzieUt8cHCAfIdiXhMZk2FTOpmVb0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=WI0cvqzf6ICzHUPQbDzqx+QdSlmrOWbo2CCcNGmoalocjdW9QJ8LilPz+xj59xJcuQJdKQ7eevj2ce4lrFzbF9gkj7ZHPsMu8x2v49hs5w943ZZl8RHXN/MvIATTPhAPXQ8JNLGfUxlfjcSPj1RBoLBnXjdMun09Mb9UfMCSmMcLKStBWxUm/3eji4zA0YXX0i44aWlqqLnKG8te/CmA5WNj0cHguk8oveXd8IJSszHvkD0mKnryyloFFnCHLwL2nvm3o1QMtNx+XX579MwKcB1bRDn2If2aNXAgoFSwSe21VMzSSsVXgIgBgFn63tDH65ep0HzSe89otr8HeK3zxg== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=aDk6OKCI; dkim-atps=neutral; spf=pass (client-ip=172.234.252.31; helo=sea.source.kernel.org; envelope-from=brauner@kernel.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.org Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=aDk6OKCI; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=172.234.252.31; helo=sea.source.kernel.org; envelope-from=brauner@kernel.org; receiver=lists.ozlabs.org) Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4jJFsf6Yf2z3dWH for ; Tue, 03 Nov 2026 02:26:14 +1100 (AEDT) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 42BEC40A1D; Mon, 2 Nov 2026 15:26:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72E611F00A16; Mon, 2 Nov 2026 15:25:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793633173; bh=B1LcgTjI6osh59ZzieUt8cHCAfIdiXhMZk2FTOpmVb0=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=aDk6OKCI0ar0R/BnCnovLiGiUgsQiS5cX2Iwq/bm/oxbS1/IImKGdug7FdOjvklfD 64oCwGAK6j+ynLF1muOCW0FEO0ciDHlSkU3IC2ugiIhQRfFVM/NQ0oqazBDBhOY57h sJCWDt4wqHqEb5aSyBD/+EPtWOITuneefzTGQ8mUGHB8tDqm3gA+4PZZ3S4JIuMiZc GXmPDubR+xVQwezYvxsVrQArwRXqg2mHgtAgwVyPXxzSE4iifxjtpH179wLH+qs5l+ IW4VUxjdneaQ8roktcSnrLzCGbyg0Xatn3vQmPJgGEy5D/5zzbKmwEEMZ7lOT8pEwl qwtHvgii6pE7g== From: Christian Brauner Date: Mon, 02 Nov 2026 16:07:28 +0100 Subject: [PATCH RFC 18/27] sched/psi: mark the pressure files permanent X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , Precedence: list X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261102-work-procfs-fs-v1-18-d09a996317b3@kernel.org> References: <20261102-work-procfs-fs-v1-0-d09a996317b3@kernel.org> In-Reply-To: <20261102-work-procfs-fs-v1-0-d09a996317b3@kernel.org> To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Jann Horn , Josef Bacik , Chris Mason , Jeff Layton , NeilBrown , Eric Dumazet , Thomas Gleixner , Al Viro , Jonathan Corbet , Christoph Hellwig , Greg Kroah-Hartman , Joel Granados , Kees Cook , Jan Kara , Jan Kara , linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-um@lists.infradead.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, ntfs3@lists.linux.dev, platform-driver-x86@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, netfilter-devel@vger.kernel.org, dri-devel@lists.freedesktop.org, ibm-acpi-devel@lists.sourceforge.net, jfs-discussion@lists.sourceforge.net, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-cifs@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-mm@kvack.org, linux-sh@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, sparclinux@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-doc@vger.kernel.org, linux-serial@vger.kernel.org, linux-atm-general@lists.sourceforge.net, Takashi Iwai , linux-input@vger.kernel.org, linux-raid@vger.kernel.org, linux-ext4@vger.kernel.org, linux-modules@vger.kernel.org, linux-debuggers@vger.kernel.org, "Christian Brauner (Amutable)" , Chuck Lever X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2074; i=brauner@kernel.org; h=from:subject:message-id; bh=tXr5cu1BdmO0jHsjps1+bZ2IKVwDVWrseoizU64SWOY=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9WG7kztYrxVWs4L7JrPOz+wSfbxdD3doWh3h9ivDfs j/t3nS+jlIWBjEuBlkxRRaHdpNwueU8FZuNMjVg5rAygQxh4OIUgIl8TmNk2OS7Of/7mXtnrpvY SWw+cDKm06eJnev5ArnA2Z7Kmpt18xn+O605/1eW86zoiteWxTHfRDjWzEmrUjjwJ+3Hhezzqf8 qeAE= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 /proc/pressure/* are created when psi initializes and never removed. Say so with PROC_ENTRY_PERMANENT, procfs then calls into them without pinning them, like it does for /proc/profile. That also takes care of a rule the files bent. psi_write() takes the seq_file's lock to serialize the triggers. A reader holds that lock while it copies to userspace, and now that procfs owns the seq_file it does that with the entry unpinned. So nothing that runs with the entry pinned may wait for that lock, and psi_write() ran pinned. Nothing ever waited for it since the files are never removed, but with the files permanent nothing runs pinned at all. Signed-off-by: Christian Brauner (Amutable) --- kernel/sched/psi.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 3132105bf382..9811c3b705eb 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1622,6 +1622,7 @@ static int psi_fop_release(struct inode *inode, struct file *file) } static const struct proc_ops psi_io_proc_ops = { + .proc_flags = PROC_ENTRY_PERMANENT, .proc_show = psi_io_show, .proc_write_buf = psi_io_write, .proc_poll = psi_fop_poll, @@ -1629,6 +1630,7 @@ static const struct proc_ops psi_io_proc_ops = { }; static const struct proc_ops psi_memory_proc_ops = { + .proc_flags = PROC_ENTRY_PERMANENT, .proc_show = psi_memory_show, .proc_write_buf = psi_memory_write, .proc_poll = psi_fop_poll, @@ -1636,6 +1638,7 @@ static const struct proc_ops psi_memory_proc_ops = { }; static const struct proc_ops psi_cpu_proc_ops = { + .proc_flags = PROC_ENTRY_PERMANENT, .proc_show = psi_cpu_show, .proc_write_buf = psi_cpu_write, .proc_poll = psi_fop_poll, @@ -1655,6 +1658,7 @@ static ssize_t psi_irq_write(struct file *file, char *buf, size_t nbytes, } static const struct proc_ops psi_irq_proc_ops = { + .proc_flags = PROC_ENTRY_PERMANENT, .proc_show = psi_irq_show, .proc_write_buf = psi_irq_write, .proc_poll = psi_fop_poll, -- 2.53.0