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 E9CDCE74AC8 for ; Tue, 3 Dec 2024 19:56:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 382456B007B; Tue, 3 Dec 2024 14:56:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 331F36B0082; Tue, 3 Dec 2024 14:56:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 220C86B0083; Tue, 3 Dec 2024 14:56:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 061BA6B007B for ; Tue, 3 Dec 2024 14:56:44 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 7DEADA0BF8 for ; Tue, 3 Dec 2024 19:56:44 +0000 (UTC) X-FDA: 82854704898.19.D6B18A1 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf30.hostedemail.com (Postfix) with ESMTP id AD01A80017 for ; Tue, 3 Dec 2024 19:56:13 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=ji8f1Xi3; spf=none (imf30.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1733255793; 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=Ysjf2OBPK+7lL0p0Kkrh9+GmuYhpmnc7ExeCH0spffo=; b=wtBHMQjcXDweXmIMn+DpV9cWBErS/Bm+GCjHxMVjaFWZBfcua57cWgfW6TovdKGLp+enre qfNloH8bRpu7mp+3bpDZxD+92sD7hKUlVhg0zPV9rYLgSTmUaeJfugqR19ECk28jfrFYyU KshQLB2OGzdWqHn97gWaCHuksMu+ZE8= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1733255793; a=rsa-sha256; cv=none; b=XepwjXNJJQ48d8e8t8FJb2Pqic31E063QXD7LFjc66z9iPERYpAiLZh4d5owd72xDpQRd+ vFzCJARyAJa3CDz4P5mo4hEDFlkC0YaHXvWxNZuDfInQWc24j20cAfJoTAJBue2OTnjAIK PPMDM6yVxuha8xlxcPdKYBqE+MsGcKc= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=ji8f1Xi3; spf=none (imf30.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Ysjf2OBPK+7lL0p0Kkrh9+GmuYhpmnc7ExeCH0spffo=; b=ji8f1Xi3aYkLJFJGb8+khtGU/W n1mXpETW+aegAdcTfhspyKITv4jJtQZF2i/Rj28KUk9B4et7yzK2r8kuwxNHtYSEHrrZZfM7co2eA SZmM8lpyr5AAp1oHIpOzXRx+MM3yPckQU6Jgdb3HtkilRj+vN4x1Q9gGj+waIyXmCD9ddxWHffXV5 TLQAjVEtnFGL47EzoQqJ9bIEf5vA3RQs4qqwfAWygH1uSP/tCLJ6p5P7smRI2pTx+aX60Fdd0XdtF MIWB3JkQrpe4de4V83SYzGBHqh2dMilQjh4jpwTZbVAtCEOh0QT330YD+uiWqVnJ6W0+MMazb0OK8 +oNL7mJA==; Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tIZ0d-0000000AAHe-0Qcw; Tue, 03 Dec 2024 19:56:35 +0000 Date: Tue, 3 Dec 2024 19:56:34 +0000 From: Matthew Wilcox To: Uladzislau Rezki Cc: Kefeng Wang , zuoze , gustavoars@kernel.org, akpm@linux-foundation.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, keescook@chromium.org Subject: Re: [PATCH -next] mm: usercopy: add a debugfs interface to bypass the vmalloc check. Message-ID: References: <57f9eca2-effc-3a9f-932b-fd37ae6d0f87@huawei.com> <92768fc4-4fe0-f74a-d61c-dde0eb64e2c0@huawei.com> <76995749-1c2e-4f78-9aac-a4bff4b8097f@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: AD01A80017 X-Stat-Signature: wnf4um4d53jf8re5dip5n4gk6ayn8kkx X-Rspam-User: X-HE-Tag: 1733255773-277043 X-HE-Meta: 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 Wjwy7Aah /pywhVFQWTCt4wxoO161GltHgi1LIt1v7aw0cBXPsg6NTW+oOgcH3++q+lRRXSuF+Qcme2DIhylqS5U2a5DGu8ZuFlBZH5IM98UNdjOqQpuYOcKDwqiHOTKWbpl0iUQQVauBYNyP/9o1yWxt3IA8fnkfLnv4FztmJNQV+lYZ8zcSpiZqTaq6Y7s5jg7pxH5zNaRHupUSGSnAt2SU0jJuHEBKpCFUioq00Yelg 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 Tue, Dec 03, 2024 at 08:02:26PM +0100, Uladzislau Rezki wrote: I think there are a few other things we can try here. First, if the copy is small (and I still don't have an answer to that ...), we can skip the vmalloc lookup if the copy doesn't cross a page boundary. Second, we could try storing this in a maple tree rather than an rbtree. That gives us RCU protected lookups rather than under a spinlock. It might even be worth going to a rwlock first, in case the problem is that there's severe lock contention. But I've asked for data on spinlock contention and not received an answer on that either, so I don't know what to suggest. Anyway, NACK to the original patch; that's just a horrible idea.