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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10CD1C43334 for ; Thu, 2 Jun 2022 17:28:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237543AbiFBR2Q (ORCPT ); Thu, 2 Jun 2022 13:28:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60982 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231461AbiFBR2O (ORCPT ); Thu, 2 Jun 2022 13:28:14 -0400 Received: from mail-qk1-x731.google.com (mail-qk1-x731.google.com [IPv6:2607:f8b0:4864:20::731]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9ADFE21E3E for ; Thu, 2 Jun 2022 10:28:13 -0700 (PDT) Received: by mail-qk1-x731.google.com with SMTP id r84so4140470qke.10 for ; Thu, 02 Jun 2022 10:28:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=GuOinXdzP0oJ6BfwGVGRF9opnqUN4LYO3Y/RmknOScs=; b=nERzx0gJZv2PpNEuSU7ZGuwa6QR4KAFkZQcX+7G15YcgRySvW6qb9+1khratoVExRd E2cV1E+y5eNUdrv7iEhYvw6adm9tR0J0w0Y5RG/qlzn3N/ExPpw5VFSVcBiyiAfseShj RtXbQnx/36eWCdWlBGeV1GIY74fg8syx0d0tBb6JCdM+OFqTrueuf3t4tmn+ivjrfwFi G+YqxQ/XoZIxp/zm5ZUgHxZvv3ENrre3J5G2iipdg5D6ioSBpapAVxA8rxNBc3hfH6JN xgR8Rb7bKKjuhDjx6rhbKloVBy4fbfQj9wlUkZziCVhgTTnOfjGMKfLsZNNy+YXFPJkc II8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=GuOinXdzP0oJ6BfwGVGRF9opnqUN4LYO3Y/RmknOScs=; b=hXQuRDngy61y7eoPkGlMzPWCcsN+CI2PSbLaXiEyGhClMcssfwjbQn/vt8DNob3NTG qzKhlIaXkU57/IDBYkA/WNYM7rLkU7uNCTQhCueKd5V0Mk3D1cB96d9adVKVDp7dQLqd L7mb8+0VvNa9VTI/u4ZjVIu9IWfAnlsYZQXFpFlPWvCTIgs7vZYeLg1sSJkS4fGDrvVt 4QtiIaOwlwYMv0LccwSln68nzLYGP0C/DuOM4Q3q3ArjxDIrZKzDul/tMI5obegxQn4X FjYsje/XInbLb1hYw/W7A93sOksHxe+p/nTEDVMnv48S3uPAD33FntTtVv3wZfOId5JS boXA== X-Gm-Message-State: AOAM531YW1D+AHZEV1rWPQYWbAoWPCsC0ZIAnaaZuIk1aFBZNQRcadpD YDiZL4Qo1raM44rOmog+bsk/MA== X-Google-Smtp-Source: ABdhPJxtqXs49dqqYwrrFL2D/sBWEpVH5naaCbeJ3Pryu+awdiRfY3cTorJuf9ghsWhGGy5AkAoh5A== X-Received: by 2002:a05:620a:f0d:b0:67e:1c14:bc5e with SMTP id v13-20020a05620a0f0d00b0067e1c14bc5emr3899163qkl.502.1654190892765; Thu, 02 Jun 2022 10:28:12 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-142-162-113-129.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.113.129]) by smtp.gmail.com with ESMTPSA id q188-20020ae9dcc5000000b0069fc13ce1f2sm3649937qkf.35.2022.06.02.10.28.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Jun 2022 10:28:12 -0700 (PDT) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1nwocF-00GUaJ-Fg; Thu, 02 Jun 2022 14:28:11 -0300 Date: Thu, 2 Jun 2022 14:28:11 -0300 From: Jason Gunthorpe To: Logan Gunthorpe Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Stephen Bates , Christoph Hellwig , Dan Williams , Christian =?utf-8?B?S8O2bmln?= , John Hubbard , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy , Martin Oliveira , Chaitanya Kulkarni , Ralph Campbell , Bjorn Helgaas Subject: Re: [PATCH v6 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem() Message-ID: <20220602172811.GN2960187@ziepe.ca> References: <20220407154717.7695-1-logang@deltatee.com> <20220407154717.7695-21-logang@deltatee.com> <20220527125501.GD2960187@ziepe.ca> <20220527190307.GG2960187@ziepe.ca> <20220602000038.GK2960187@ziepe.ca> <400baba7-1cd6-09d4-4de9-2a73f08afc79@deltatee.com> <20220602163059.GL2960187@ziepe.ca> <51cc6645-2504-6d01-5626-238ed6ffff04@deltatee.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51cc6645-2504-6d01-5626-238ed6ffff04@deltatee.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Jun 02, 2022 at 10:49:15AM -0600, Logan Gunthorpe wrote: > > > On 2022-06-02 10:30, Jason Gunthorpe wrote: > > On Thu, Jun 02, 2022 at 10:16:10AM -0600, Logan Gunthorpe wrote: > > > >>> Just stuff the pages into the mmap, and your driver unprobe will > >>> automatically block until all the mmaps are closed - no different than > >>> having an open file descriptor or something. > >> > >> Oh is that what we want? > > > > Yes, it is the typical case - eg if you have a sysfs file open unbind > > hangs indefinitely. Many drivers can't unbind while they have open file > > descriptors/etc. > > > > A couple drivers go out of their way to allow unbinding while a live > > userspace exists but this can get complicated. Usually there should be > > a good reason. > > > > The module will already be refcounted anyhow because the mmap points > > to a char file which holds a module reference - meaning a simple rmmod > > of the driver shouldn't work already.. > > Also, I just tried it... If I open a sysfs file for an nvme device (ie. > /sys/class/nvme/nvme4/cntlid) and unbind the device, it does not block. > A subsequent read on that file descriptor returns ENODEV. Which is what > I would have expected. Oh interesting, this has been changed since years ago when I last looked, the kernfs_get_active() is now more narrowed than it once was. So manybe sysfs isn't the same concern it used to be! Thanks, Jason