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 7317FC7EE2A for ; Wed, 25 Jun 2025 18:00:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F26B86B00D2; Wed, 25 Jun 2025 14:00:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EFEA86B00D3; Wed, 25 Jun 2025 14:00:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E14266B00D4; Wed, 25 Jun 2025 14:00:28 -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 D447F6B00D2 for ; Wed, 25 Jun 2025 14:00:28 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 779D01216D5 for ; Wed, 25 Jun 2025 18:00:28 +0000 (UTC) X-FDA: 83594687736.27.B67561B Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf02.hostedemail.com (Postfix) with ESMTP id F3DCB80009 for ; Wed, 25 Jun 2025 18:00:25 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="O036/4Ph" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1750874426; 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=jk1v+l0g9eTmQlXNCeuyS9ezhYiOOgaiu8K1KIm6yfc=; b=nmmlAVyZrK2gHqf00WsOFAD3wBxs0oPaujFCYDetlNwoAdjK/9rvtkTNZ2I2Q9Gbk4Y4+M wrGbAOjB/6XdYWnoLh2HerOaY1YP94hh1PaQTM5OmmQBlcZrDYU51QjiXQpTi1qj2qszjl sv3SNMF009F5Vmfpbjup8gG7/KbQe+4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1750874426; a=rsa-sha256; cv=none; b=AMsPisUSNKIObJ7VwTTJDMk/X07ft9qNVuozBC0fAEtbbnf8MckbriskQCfTjr6R17dddU mHjewePGSi9SIr2BUWTOF+XMdCSpohEatv6eASDQjQtEN5S8Lu6AhtmVcEusEOLBIvQYUU lMkj4zagfG2/CrD3UlcvSUz4mJs+TnM= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="O036/4Ph"; spf=none (imf02.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=jk1v+l0g9eTmQlXNCeuyS9ezhYiOOgaiu8K1KIm6yfc=; b=O036/4Phc22K9QKb+v6Gh3g7NM gsw8QmLdsNDS4PDUNQC76lpnWZNTnF7tdWiPWjY/d1vl9BzjCZeWy5ngkoTMgLzNvn34YA7tExdpa DGXfZqGj0qD52xRqEusY9jAJa5T+eo2MVcBOkmih5ri+xCFbRG5iJleA51oe4SqfT6+g7f8bB6opD Xf4WPMj/fGaEZqDym+xT4dM1WkHB3639zellOest8jzRgf5/CJQr+kZnpes5k9i/SwsELrrarKIiz ENOB4fjBAtjlJq53lXw3OwzwGjl38abe7AQXwtVdsr2HRwP0t+clF/XnLRqj6UJnz63b1MpKVe8uR nyxpqaWQ==; Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uUUQ3-00000009tzy-0TRJ; Wed, 25 Jun 2025 18:00:23 +0000 Date: Wed, 25 Jun 2025 19:00:22 +0100 From: Matthew Wilcox To: "Vishal Moola (Oracle)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Jordan Rome , Andrew Morton Subject: Re: [RFC PATCH 1/3] mm/memory.c: convert __copy_remote_vm_str() to folios Message-ID: References: <20250625174841.1094510-1-vishal.moola@gmail.com> <20250625174841.1094510-2-vishal.moola@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250625174841.1094510-2-vishal.moola@gmail.com> X-Rspam-User: X-Stat-Signature: 8nf33au7kpbhrzyg43r57kj4j9xnxdah X-Rspamd-Queue-Id: F3DCB80009 X-Rspamd-Server: rspam08 X-HE-Tag: 1750874425-950668 X-HE-Meta: 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 z2NOwAeR 8qLM7bTuuCjnfO4FK5Q3EvIhsyM7HwWBaISBTlvafJG+YWsqjAeham2YZYdZMQQQ2nHPqx6HsrX20fpEip9q6y82pAJAsRm3Cm3PX6PKrAgkJdqolDQEjFzdGIzfT/EMs8ITTJchAnHeGe0TxekzPrNva0CVnIrjkzgTDNYejBn+ushmgTh9RTf5ulDs3oBDReFlK4SVOSleDilne4bzV6YWAxEOqWwJVAr8dmzc/QiSMVWUJqIGmLnek+KzClbMtsGrpulrUEG3p8bGqZVp8NYAe6ZYPRF/hCKakIMZ+lKUzH7vupOX8K137y60R3K2ULXuQJNRZL8FHfj0= 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, Jun 25, 2025 at 10:48:39AM -0700, Vishal Moola (Oracle) wrote: > +++ b/mm/memory.c > @@ -6820,9 +6820,10 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, > } > > while (len) { > - int bytes, offset, retval; > + int bytes, folio_offset, page_offset retval; offset_in_folio() returns a size_t so that we can support folios larger than 2GB (which is a real possibility here; hugetlbfs might end up with a 16GB folio on some architectures). > @@ -6837,17 +6838,20 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, > goto out; > } > > + folio = page_folio(page); > bytes = len; > - offset = addr & (PAGE_SIZE - 1); > - if (bytes > PAGE_SIZE - offset) > - bytes = PAGE_SIZE - offset; > + folio_offset = offset_in_folio(folio, addr); Umm. Not sure this is safe. A folio might be mapped misaligned, so 'addr' might not give you the right offset within the folio. I think you might need to use addr - (vma->vm_pgoff << PAGE_SHIFT). But I'd defer to others here ... particularly when it comes to anonymous folios.