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 3AB90EB64DA for ; Wed, 12 Jul 2023 15:52:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BA10E6B007B; Wed, 12 Jul 2023 11:52:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B502B6B007D; Wed, 12 Jul 2023 11:52:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A3F9B6B007E; Wed, 12 Jul 2023 11:52:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 9286A6B007B for ; Wed, 12 Jul 2023 11:52:40 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 33573802CC for ; Wed, 12 Jul 2023 15:52:40 +0000 (UTC) X-FDA: 81003402480.15.1E17DA2 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf17.hostedemail.com (Postfix) with ESMTP id 085FB40023 for ; Wed, 12 Jul 2023 15:52:37 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=qCstPNzq; spf=none (imf17.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-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689177158; a=rsa-sha256; cv=none; b=ZAQtEGb8XNiIgyTKMPuh+q+hKS23UPEJVyp6EKxMHBRgCYv3v4pJls0EKBuCTTRjbNn+Oe ejlmGE3Ir9LgJNL1VPByWiwCI4uxdAUsgTFxj+ZPrVGk+G8wdxkzdiWno/dk0hUexuPUqX Wccyl641XZiveBok+SNjKTHcQIT9Yos= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=qCstPNzq; spf=none (imf17.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=1689177158; 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=t6xhwQrsPO2xAOUaQCrsjH8BtGFPxhY45ODgMz3mJqw=; b=rFzH1k/CnzTGZXqsTe83KW3uIpaQRlB21psJh3EgM+PiQ9rR7VI79FLptkDBEipfBu+s/i Px1Q63JKVh5tMO/qXrmCyOMj7NdmWblToTvwBfoAOANQvYcPUV9zqiBYjy34d4u3PdWPqo 0uo3f4E5nhG19FhH4Z2b77LhFgOvj9U= 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=t6xhwQrsPO2xAOUaQCrsjH8BtGFPxhY45ODgMz3mJqw=; b=qCstPNzqtwZAhgwkH/rNi5zZYe 8qiKgCS1mPV4cZ15tM3iTjPjJwhRqURCCvuJRE7r9gAsYpp55xXX3tpegaiemvijfbqikVMVaHaTs VmwjphteSVBDuQnwlAAvgcYfANiRp6FhgK3WSoBhSuAWx/n3V4+LAQE3RzZ2RTT6psEUNW9Q+MuZ3 lQ+oSsq7OqIPjRaJYAwfavsBjvuq01hn0aaaAvHwT+8XSEUD0FTUIQfE98lVhlkZaAddXAQru8tzs Na+gl7wbIFrHmcdaQxZCM4mA/vkXdmKCcp3ZxOd5VjAPaDm+p5C8Vnf1upOMwoebxwppXqu947Jc9 g6SsO3jw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qJc8i-00GqHI-54; Wed, 12 Jul 2023 15:52:28 +0000 Date: Wed, 12 Jul 2023 16:52:28 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: David Hildenbrand , Dan Carpenter , linux-mm@kvack.org, Andrew Morton , "Liam R. Howlett" , Laurent Dufour , Michel Lespinasse , Jerome Glisse , Michal Hocko , Vlastimil Babka , Johannes Weiner , Peter Xu , Dimitri Sivanich , Mike Travis , Steve Wahl Subject: Re: [bug report] mm: replace vma->vm_flags direct modifications with modifier calls Message-ID: References: <9704a138-60e6-4ede-91f0-844e1df2ad84@moroto.mountain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 085FB40023 X-Stat-Signature: yztwjwrfzi71fgbxp1g3manmiceh8qyy X-Rspam-User: X-HE-Tag: 1689177157-379430 X-HE-Meta: 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 Sad9pK1d ulbeDRRmsYqM0Y1j+uvkBvHCJphfRHURvLq8mWcoH3clKKyAof7WxpwXse5VWzCOmDIM+XNsigNgZtMbtJl4bj8BzEf5QxGfOCP6F+nKT37UxvD9BIHvnDEJD8UOsLVEbJXgYVPvwjGcalrI2Sc40/Dq47zWTPxQDjPCRrDFus+AvkxYLTPXdRheE6g== 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 Wed, Jul 12, 2023 at 08:01:18AM -0700, Suren Baghdasaryan wrote: > Are you suggesting to break remap_pfn_range() into two stages > (remap_pfn_range_prepare() then remap_pfn_range())? > If so, there are many places remap_pfn_range() is called and IIUC all > of them would need to use that 2-stage approach (lots of code churn). > In addition, this is an exported function, so many more drivers might > expect the current behavior. You do not understand correctly. When somebody calls mmap, there are two reasonable implementations. Here's one: .mmap = snd_dma_iram_mmap, static int snd_dma_iram_mmap(struct snd_dma_buffer *dmab, struct vm_area_struct *area) { area->vm_page_prot = pgprot_writecombine(area->vm_page_prot); return remap_pfn_range(area, area->vm_start, dmab->addr >> PAGE_SHIFT, area->vm_end - area->vm_start, area->vm_page_prot); } This is _fine_. It is not called from the fault path, it is called in process context. Few locks are held (which ones aren't even documented!) The other way is to set vma->vm_ops. The fault handler in vm_ops should not be calling remap_pfn_range(). It should be calling set_ptes(). I almost have this driver fixed up, but I have another meeting to go to now.