From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A26CA372698; Fri, 15 May 2026 08:05:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778832332; cv=none; b=QJCt9/O76gFG3aVdftKyZIN8OnFR420xgUmD25PadlxNc8FwXQEJTqqjIWyTc22pnOI7DW/hBxJoZOfwEqmbZdYfE1Gb4MRS7W9IG2cM4uHiiqBCrWqb0565GfrEDdpuD5Is18SqObUcxgOErRPYKXz76sjy/QSSikY+gx/fDYQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778832332; c=relaxed/simple; bh=YC+m8abWFopx+Nm486DLqohl3gVgRQtOHlTAMvs/kk0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tkApnlyFQbgdJkKepZzIJBJW0sj9l39mNGgYfQ0bkZqwXET6Ci1RhIaPCs5YfumDL7XHgWy7Vtldri4qBx5ARGwV+iFrOC9zD0hLznsvHI+cAwzEyiBWpk26kOu101/6f5zqSHFkT50M6+JPQd6J9gwVI10WmMa6cht3cQZNlzo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pLnyVZ8R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="pLnyVZ8R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF3F6C2BCB0; Fri, 15 May 2026 08:05:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778832332; bh=YC+m8abWFopx+Nm486DLqohl3gVgRQtOHlTAMvs/kk0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pLnyVZ8R4I7HF0X54h1Yu3TMm34hPVVkkKDkv2wFVxL/fdm/bBgi/Eu2mw+WgeFq3 ilqTA+Dj4oLvtvXLOHm7wt4nTatOWl5AwU1FlkednCKQUsb/wdR+b6OVa5t1whFSWE /I4rEDN2WMiGvUN4z2HbTQLNSVTy5oWpVNEw/ZbM= Date: Fri, 15 May 2026 10:05:36 +0200 From: Greg KH To: Jianlin Lv Cc: corbet@lwn.net, skhan@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, jianlv@ebay.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, driver-core@lists.linux.dev Subject: Re: [PATCH] driver core: Add cmdline option to force probe type Message-ID: <2026051558-spiffy-same-f3bb@gregkh> References: <20260514094955.76305-1-jianlv@ebay.com> <2026051443-exuberant-important-534f@gregkh> <2026051406-corridor-equation-c50e@gregkh> <2026051532-pettiness-gave-1127@gregkh> Precedence: bulk X-Mailing-List: driver-core@lists.linux.dev 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 Fri, May 15, 2026 at 03:54:17PM +0800, Jianlin Lv wrote: > On Fri, May 15, 2026 at 2:13 PM Greg KH wrote: > > > > On Thu, May 14, 2026 at 11:09:03PM +0800, Jianlin Lv wrote: > > > On Thu, May 14, 2026 at 9:49 PM Greg KH wrote: > > > > > > > > On Thu, May 14, 2026 at 09:35:08PM +0800, Jianlin Lv wrote: > > > > > On Thu, May 14, 2026 at 6:16 PM Greg KH wrote: > > > > > > > > > > > > On Thu, May 14, 2026 at 05:49:55PM +0800, Jianlin Lv wrote: > > > > > > > From: Jianlin Lv > > > > > > > > > > > > > > Device drivers that use asynchronous probing can cause non-deterministic > > > > > > > device ordering and naming across reboots. A typical example is storage > > > > > > > drivers (like sd/nvme): asynchronous probing can lead to inconsistent disk > > > > > > > logical names after reboot. In scenarios where disk naming consistency is > > > > > > > critical, the probe type should be set to synchronous. > > > > > > > > > > > > > > This patch introduces a driver_probe kernel parameter that overrides any > > > > > > > driver's hard-coded probe type settings and allows runtime control without > > > > > > > requiring kernel recompilation: > > > > > > > > > > > > > > driver_probe=PROBE_TYPE_SYNC,nvme,sd # Force specific drivers sync > > > > > > > driver_probe=PROBE_TYPE_ASYNC,*,usb # Force all async except usb > > > > > > > driver_probe=PROBE_TYPE_SYNC,* # Force all drivers synchronous > > > > > > > > > > > > > > The implementation replaces the limited driver_async_probe parameter with > > > > > > > a more flexible interface that can force either synchronous or asynchronous > > > > > > > probing as needed. > > > > > > > > > > > > > > Signed-off-by: Jianlin Lv > > > > > > > --- > > > > > > > .../admin-guide/kernel-parameters.txt | 27 +++++-- > > > > > > > drivers/base/dd.c | 71 ++++++++++++++----- > > > > > > > 2 files changed, 74 insertions(+), 24 deletions(-) > > > > > > > > > > > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > > > > > > index 4d0f545fb3ec..b43a8bd20356 100644 > > > > > > > --- a/Documentation/admin-guide/kernel-parameters.txt > > > > > > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > > > > > > @@ -1377,12 +1377,27 @@ Kernel parameters > > > > > > > it becomes active and is searched during signature > > > > > > > verification. > > > > > > > > > > > > > > - driver_async_probe= [KNL] > > > > > > > - List of driver names to be probed asynchronously. * > > > > > > > - matches with all driver names. If * is specified, the > > > > > > > - rest of the listed driver names are those that will NOT > > > > > > > - match the *. > > > > > > > - Format: ,... > > > > > > > > > > > > You can not remove an existing user/kernel api, sorry, that is not > > > > > > allowed as you just broke all systems that were relying on this :( > > > > > > > > > > > Could you provide more suggestions on how to improve this patch? > > > > > > > > Not really, sorry, I don't think this is a change that should be done at > > > > all. disk naming is a long-solved issue, to think that you can fix that > > > > by doing sync/async device probing is not understanding both the issues > > > > involved, and how we solved it already :) > > > > > > Do you mean referencing disks via by-path/by-id? > > > > No, use something that does not change, like filesystem labels or > > serial numbers, or something else that is guaranteed unique. > > > > > In our production env > > > they can also be unstable; this is an example I encountered before: > > > https://lore.kernel.org/all/CAFA-uR_jk6jCmf9DTebSVBRwtoLuXuyvf1Biq+OObqRVAOZbBw@mail.gmail.com/ > > > > Yes, paths can, and will, change. Don't use them. > > > > Why not use a UUID, that is explicitly what those are designed for. > > For cloud deployment, the local volume provisioner detects > and creates PVs for each local disk on the host, and it cleans up > the disks when they are released. > The local volume provisioner is deployed in the cluster as > DaemonSet. For the same SKU, it uses a single, unified configuration > file to initialize local disks. In this scenario, UUIDs are not applicable. > In our case, logical names are used to identify the disk. Ok, but again, there is NEVER a guarantee that those logical names are going to be the same across boots. Please NEVER rely on them if you wish to mount things properly. Use a label on the filesystem instead. Or something else, you have loads of possibilities here. Attempting to manipulate driver sync/async order is not going to solve your problem at all. > > > I understand that device naming in the kernel can change at any time. However, > > > Is it necessary to provide an interface that allows users to choose > > > the probe mode themselves? > > > > It's not going to solve your problem, so I wouldn't worry about it. And > > you can't remove it, although I really would like to :) > > OK，Is the reason we can’t change the priority of driver_async_probe setting that > the original logic has changed, i.e. it would alter the original behavior? Because it is a user api that people might be relying on for various unknown reasons. thanks, greg k-h