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 2BA703655FA; Thu, 14 May 2026 18:37:56 +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=1778783877; cv=none; b=Gtgwh/HmRTgAqFQyZ80UOkTWkn38/U/Ur2+X5ogyTsPeoyoMGvHRDWUngO1fDmnCKh1kbrIdHKAnTZrL5yotPQR+LOD5zUwSxFtoj0Y1d3rJOwLRpnpoVtLUXdXGILW7RglhcFxnbzG9NBmsmhH3EkkNjxHu2HwT0AX7VD6CfMA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778783877; c=relaxed/simple; bh=cyAjpV+6FMx9SmPOLKPO2HTdcek3f7cftPGWL1rQdSA=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Gtk1eJNVyKa485UyjZY/kUev52HbIUN+FT50eHvCkQab9LJdEJdZujHwZYiDphE5nNI0q5ueMkUtnM41+SBFIMuJR+lZLbW0rtCJ/OJr991lCLgn/1lFe6a6ww6Xt0FcupZeXDJRDuL5ow4hxHHwQKgC10LrNe7Szpo9murhepQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Y6FWLz5i; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Y6FWLz5i" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B605C2BCB3; Thu, 14 May 2026 18:37:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778783876; bh=cyAjpV+6FMx9SmPOLKPO2HTdcek3f7cftPGWL1rQdSA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Y6FWLz5ixhUzXzW/VtZMAfBoMbWeazxqKQK+3Ece8oDuWJpvNZbwacmagkYZ4qPMO mYssfA1l+bj1l12jdc2E5i3jXHpampkmtzBEb167PEKdP0Nm5GIJDW+RUon97FUP9H krgZQdenwByA24yE/qKvVZrnWmFmPvij7S144lhewcBHCv1MuUjkjzyjDeW0hdmwV1 HKeVKK4S4Gbr1YTIbIOUFswecHIq6nT0Ira0tmo0/CUis5D0FA7UHr+fZBPbXQkXpu K2YoUJ0vqE/IwWnApg8wnC5BG87dNR/VmPX1ltV/aJlGytK/3YhkXkTiGTVWzAD3Nd XjQiLAqLOXJuw== Date: Thu, 14 May 2026 19:37:49 +0100 From: Jonathan Cameron To: Chen Pei Cc: alison.schofield@intel.com, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, guoren@kernel.org Subject: Re: [ndctl PATCH 2/2] daxctl, util/sysfs: skip module probe-insert when driver is builtin or live Message-ID: <20260514193749.0f0750e2@jic23-huawei> In-Reply-To: <20260514063234.86439-3-cp0613@linux.alibaba.com> References: <20260514063234.86439-1-cp0613@linux.alibaba.com> <20260514063234.86439-3-cp0613@linux.alibaba.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 14 May 2026 14:32:34 +0800 Chen Pei wrote: > kmod_module_probe_insert_module() is supposed to return 0 for builtin > modules, but only when libkmod can locate the modules.builtin index. If > the index is missing or out of sync, libkmod falls through to the real > init_module() syscall and returns an error such as -ENOENT, producing a > spurious "insert failure" even though the driver is already part of the > running kernel. > > Pre-check kmod_module_get_initstate() and short-circuit when the module > is KMOD_MODULE_BUILTIN or KMOD_MODULE_LIVE, matching the pattern used by > ndctl's own test/core.c. So I happened to run into exactly this print earlier today and was very happy to see this resolving it! I'm lazy so when developing in a VM tend to do everything I care about built in and not bother with installing the modules. However - despite having CONFIG_DEV_DAX = y in the kernel, I'm getting a state of KMOD_MODULE_COMING which is curious as there is no initstate file to read that from. Looking at the code in libkmod it seems to first check if it can open /sys/modules/device_dax/initstate and if it can't checks if the directory /sys/modules/device_dax/ exists. If it finds that it returns KMOD_MODULE_COMING which seems odd given in a fully initialized built in driver that particular set of circumstances is normal. Any ideas? To me the description above is misleading if we need to have something else for the builtin case to work. I'm out of time to today but may get time to look at this tomorrow and chase down if there is a way to get it to work. Jonathan > > For builtin modules the local kmod reference is dropped because builtin > drivers cannot be unloaded; for live modules the reference is retained > in dev->module, matching the post-probe-success behavior. > > Signed-off-by: Chen Pei > --- > daxctl/lib/libdaxctl.c | 18 ++++++++++++++++-- > util/sysfs.c | 17 +++++++++++------ > 2 files changed, 27 insertions(+), 8 deletions(-) > > diff --git a/daxctl/lib/libdaxctl.c b/daxctl/lib/libdaxctl.c > index ffc81eb..42bfc39 100644 > --- a/daxctl/lib/libdaxctl.c > +++ b/daxctl/lib/libdaxctl.c > @@ -910,7 +910,7 @@ static int daxctl_insert_kmod_for_mode(struct daxctl_dev *dev, > const char *devname = daxctl_dev_get_devname(dev); > struct daxctl_ctx *ctx = daxctl_dev_get_ctx(dev); > struct kmod_module *kmod; > - int rc; > + int state, rc; > > rc = kmod_module_new_from_name(ctx->kmod_ctx, mod_name, &kmod); > if (rc < 0) { > @@ -919,7 +919,21 @@ static int daxctl_insert_kmod_for_mode(struct daxctl_dev *dev, > return rc; > } > > - /* if the driver is builtin, this Just Works */ > + /* If the driver is builtin or already live, skip probe-insert. */ > + state = kmod_module_get_initstate(kmod); > + if (state == KMOD_MODULE_BUILTIN) { > + dbg(ctx, "%s: module %s is builtin\n", devname, > + kmod_module_get_name(kmod)); > + kmod_module_unref(kmod); > + return 0; > + } > + if (state == KMOD_MODULE_LIVE) { > + dbg(ctx, "%s: module %s already loaded\n", devname, > + kmod_module_get_name(kmod)); > + dev->module = kmod; > + return 0; > + } > + > dbg(ctx, "%s inserting module: %s\n", devname, > kmod_module_get_name(kmod)); > rc = kmod_module_probe_insert_module(kmod, > diff --git a/util/sysfs.c b/util/sysfs.c > index e027e38..641b86d 100644 > --- a/util/sysfs.c > +++ b/util/sysfs.c > @@ -183,12 +183,17 @@ int __util_bind(const char *devname, struct kmod_module *module, > } > > if (module) { > - rc = kmod_module_probe_insert_module(module, > - KMOD_PROBE_APPLY_BLACKLIST, > - NULL, NULL, NULL, NULL); > - if (rc < 0) { > - log_err(ctx, "%s: insert failure: %d\n", __func__, rc); > - return rc; > + /* Skip probe-insert when the module is already builtin or live. */ > + int state = kmod_module_get_initstate(module); > + > + if (state != KMOD_MODULE_BUILTIN && state != KMOD_MODULE_LIVE) { > + rc = kmod_module_probe_insert_module(module, > + KMOD_PROBE_APPLY_BLACKLIST, > + NULL, NULL, NULL, NULL); > + if (rc < 0) { > + log_err(ctx, "%s: insert failure: %d\n", __func__, rc); > + return rc; > + } > } > } >