From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=213.95.11.211 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793961730; b=SY91GNFgFGN+ibXm9JoThmuszOkkNshybqBmSaPaV1amdjtiPTMlVOwAi8e6USY/9EC/ yqmHS7x7ZXofUkA71AnrqVJclhDBDh1LPCg1UURzoOQaWbOjIXoYc/I32ZGfSj3nPqOeg /nDDZs5I/5wQlesLCSnVo70vGb4lSYHkh+1VMWSGYEKP9koRD92fFXuQyaSvYbcBDSPwf rq1BAtb/KKWkPU62oZYo+qADJfsbqaS9G7vzCDZ3ChzKWbi31jHekg0MzOafYWsNt9rLe sTWqli5MZ45Ujba5g1BODUbYUQWnFUpa5L1uTyqSLrafJPtT0jyJXzsSpoR+JAjfa/A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793961730; h=DMARC-Filter:Received:Date:From:To:Cc:Subject:Message-ID:References: MIME-Version:Content-Type:Content-Disposition:In-Reply-To:User-Agent; bh=Y9kFrNqpqE15U9jIYdrxg+czSD6JG0cMxUhVLzPeOPE=; b=kIa3PH5BS3OIb+h3RqNPlpR0k4ceLYvkZiTmmCmtc93hU9NdeKapHG9R8Xi8hhaJJ8Hx s5c2FivCWdJ7jQPwTe0ggM98rg8K98o2Wp3fOn8xc/wOfpYfbrqDuTi+YcFrOrtnTaup1 tpYI94043DHybc2vzbHAUduz8h22KXMQN1ajrvy6F3U/RInuDFlDR+o9XC0pnVT512lcK 3ukjDMVllERLZkos0qpsMj73BnDNx4QIf1fziDcOqvVWxe23eF0xP2B2dggMRKyODDhcH dqq0hlvLGQIh1pqYliOzd3nIRyM9OY9oOen9ttGj4fHY9YL7KNEa79A+zlSUGZRaVPA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.remote-ip=213.95.11.211 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B804D606A329; Fri, 6 Nov 2026 10:42:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org B804D606A329 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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) 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.