From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6D4E8606A32D for ; Fri, 6 Nov 2026 10:42:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 940E46B05B3; Fri, 6 Nov 2026 05:42:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 918756B05B4; Fri, 6 Nov 2026 05:42:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8544A6B05B5; Fri, 6 Nov 2026 05:42:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 61A4A6B05B3 for ; Fri, 6 Nov 2026 05:42:12 -0500 (EST) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 01AF4160CC3 for ; Fri, 6 Nov 2026 10:42:11 +0000 (UTC) X-FDA: 85404354504.28.ECB7B08 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf18.hostedemail.com (Postfix) with ESMTP id 39B1D1C0006 for ; Fri, 6 Nov 2026 10:42:10 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=none; spf=pass (imf18.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de; dmarc=pass (policy=none) header.from=lst.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793961730; 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; bh=Y9kFrNqpqE15U9jIYdrxg+czSD6JG0cMxUhVLzPeOPE=; b=t3xZPihrXaCQyQ7HMzgvnGNzIgFZECLpB2flF1+Vl74PA3quvkL+aLhK6O2rHKuy9zVe3E ACNOWzclPOSzxzRpu6sba3AfDUCusW8Rg980MN8zC8FhscHIBvczxeKCNhpfmoW+ikk9bm mXZLV/95Tz7Y4NZ0dJoIX1hSTs+i1Vg= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793961730; b=esIkCFt7UktGgRegeTkW3DuKd/iD7rCddVCEz8LBYyj9CFBC83fszS2A9DaagZVfT+zQ4h w7AAmbVH6J1wOrLi0+IclRoJwoMStMTdqbydZmZh9xYGuSlkIbrdth4MszA3Orn/ouKPvF Zz0FxAGT9mq73fUhDXu4h6uO0ccgFyY= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=none; spf=pass (imf18.hostedemail.com: domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de; dmarc=pass (policy=none) header.from=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id CF4B168BEB; Fri, 6 Nov 2026 11:42:05 +0100 (CET) Date: Fri, 6 Nov 2026 11:42:05 +0100 From: Christoph Hellwig To: Mengmeng Zhao Cc: Jens Axboe , Dan Williams , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , tytso@mit.edu, Andreas Dilger , Baokun Li , Ojaswin Mujoo , "Ritesh Harjani (IBM)" , Zhang Yi , "Darrick J. Wong" , Andrew Morton , asml.silence@gmail.com, hch@lst.de, Anuj Gupta , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Li Wang Subject: Re: [RFC 2/6] mm/filemap: refuse dmabuf iterators in the generic read/write copy paths Message-ID: <20261106104205.GB5668@lst.de> References: <20261105065847.196540-1-mengmeng.zhao@linux.dev> <20261105065847.196540-3-mengmeng.zhao@linux.dev> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261105065847.196540-3-mengmeng.zhao@linux.dev> User-Agent: Mutt/1.5.17 (2007-11-01) X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam09 X-Stat-Signature: yax685ctfxb3acrejop4kb38yxhuq3c5 X-Rspamd-Queue-Id: 39B1D1C0006 X-Rspam-User: X-HE-Tag: 1793961730-847802 X-HE-Meta: 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 ls6f1i3d aDbBCUBhRaX+mc6VR7JpwMDSASHrSASnl1KRk1oDtYeKczZauSag2NpijpZPgk6yoF+CUPbgTyZnm1p4yKyKJuierc5Mamcg8GVouaB63e/C1MMaa6DWMvtU4rsvP6kC0KaFZTw1cX85j6dEzFt2CpdHmuzdIPrEnwFwKLSAmSbnIeqs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Nov 05, 2026 at 02:58:43PM +0800, Mengmeng Zhao wrote: > From: Mengmeng Zhao > > The generic copy helpers cannot touch device memory. Which generic copy helpers? This doesn't seem to touch copy_file_range at all. > Refuse a > dmabuf iterator in generic_perform_write() and the filemap_read() > fallback while keeping any direct-I/O progress, and report a busy > folio from generic_file_direct_write() as -EAGAIN instead of asking > for the buffered fallback such an iterator cannot take. I suspect the fallback code in the callers might be a better stop for this.