From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CD02C3191D6; Thu, 23 Jul 2026 06:11:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784787085; cv=none; b=BnvpvhSdb+eAOoBNyoFjly0KMwg+rF11H+yI/7ejBIdL8dZphLu7rAPIIvpsUmbh9VjIi1I+qQuI8mjkKaeR9M8DvshrtwAp9dwSQyFYt56l7WcY0f1Uw8CpSeSo+K+3womS+LIUTeIwYlPLV337VWy9KonWup4sjWvZh0BVcoY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784787085; c=relaxed/simple; bh=Qae+3iD0gUpcR0ak4mkDHhk+7oPwN70ONsdbSH40q5o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cI1iS3LmMja5Oz8/ygAVGHc9cbZvrAjzcRT2OabmsOr2yYGyJI+MLUHxvFgSUHkvgYf3JImR8LRp1tlxsObFZtHck7NnhnrdJIchxxo1DuqVF8z/LELhaBdriIH1gTxVtX06Ey0v7rTgWk/IApEGRlepeO6Yd1Dz6QOIA8Nebr4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jQI35ZHF; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jQI35ZHF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7994E1F000E9; Thu, 23 Jul 2026 06:11:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784787084; bh=VBdn2EWjCzaB/LsGvu5JNC2sbY5O5dhhwEkMKQrKz6Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=jQI35ZHFBTChYjQ6kfiY3FIG5lc5U7yuTiFHA0MAJuCB5lQhyHKzfGFvMqu0Vg7oS wbmqZnrDUGLV+3FxAGADTsdviVKQKmKxL5b42UsWs1FHa/mxdTow2mrTa9oHPGfiFq 7VcDodqNgInG29zaRfj9Q59DE3247biTYu4J02Ld6oUHDbnanBWeSf2IeYtx8nhSGh C4UgTQZqxfkmK2AoIZyCTBNAVlrVMRTOt7Unzfeklkfjs4POShPbXDmJPwwg+nCZOz P8UMjW2HY0eW3UKLb58b2RFEDv2qDkLqgPOUN6Ue6Zq6qTLfJTgAqH/sJ3VXsHAVsq IPE4/hdrctM0g== Date: Thu, 23 Jul 2026 09:11:18 +0300 From: Leon Romanovsky To: Mykola Marzhan Cc: Logan Gunthorpe , Jens Axboe , Song Liu , Yu Kuai , Keith Busch , Christoph Hellwig , Sagi Grimberg , linux-block@vger.kernel.org, linux-raid@vger.kernel.org, linux-nvme@lists.infradead.org, Li Nan , Xiao Ni , Guoqing Jiang , Jason Gunthorpe , Kiran Kumar Modukuri , Chaitanya Kulkarni , Bjorn Helgaas , Shivaji Kant , Pranjal Shrivastava , Henrique Carvalho , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH v2 6/7] md/raid1,raid10: skip futile retries on P2PDMA mapping failures Message-ID: <20260723061118.GA110966@unreal> References: <20260719105327.864949-1-mykola@meshstor.io> <20260719105327.864949-7-mykola@meshstor.io> <9f846c85-f427-433a-b87d-8e9e3a4406e7@deltatee.com> <20260722083015.GU110966@unreal> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Jul 22, 2026 at 09:00:16PM +0200, Mykola Marzhan wrote: > > I had thoughts about this series too. It seems best to avoid > > the P2P path entirely unless all legs support P2P. > > > > Can the md/raid code determine P2P support in advance? > > Yes, and it already does: the block layer ANDs the P2PDMA queue > feature across all legs, so an array with a non-P2P member > (e.g. an nvme-tcp leg) never advertises P2P at all. > > But that flag can only say "this driver can do P2P in general". > md cannot see which HCA device does the DMA for a fabrics leg — > and with multipath failover it can change at any time. > > So the up-front gate covers what is knowable up front. > This series is about the remainder. > In mixed case, one local P2P leg plus a remote replica, with it: > 1) a failed read just redirects to a capable mirror; > 2) a failed write records bad blocks instead of retrying forever. Thanks for the explanation. > > Mykola >