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 8C2A8224FA; Sun, 21 Dec 2025 03:30:24 +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=1766287824; cv=none; b=nG0/izbMiJhPLAwuHPAGgkun+qEb/tXuNY+pSkzr9gLLWP9fWilt63TEW2q+EnDqbaCzLDGkjKjsXusGwR9n7AYT17ZY8kkI7SJRs8ha4LFO+iP8FrqgKApWH1bgx9v3CjhDnaAlBRtjbfwvIcWUbVrDTfZ3pxAMxYXENAbGBkM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766287824; c=relaxed/simple; bh=213ARG2iDcjOtUajVDIH2Laug91k64/zHImj8Q3fSYo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=a9Ij6LaRjeOaZRBahoITcUptisejzrTeGiTNUcuq7yICXaT3jnl4Sq1UCcnkhvBE4feEXX4ID4/7ikv5axvwVcLRQsCNUqFVyw+dpPoUmQ6YyrDxrfB4A9YP8aXg/lRZCPTO7CGs6TheKI0X0u9U2XgWwXZMCjVKEUAocr9RD+s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U5IsKXTH; 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="U5IsKXTH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D0ECC113D0; Sun, 21 Dec 2025 03:30:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766287824; bh=213ARG2iDcjOtUajVDIH2Laug91k64/zHImj8Q3fSYo=; h=Date:Reply-To:Subject:To:Cc:References:From:In-Reply-To:From; b=U5IsKXTHqSsGJi3HgpPiB6AlfQZn0uS6xiSm5SxCZ5NMM6NZBQlTfe9b+IYr4TN+o 8Sn3L+7tZQ6EoR44jWELMP04HZgQtkDDtdNA0gB5Y3Jo5BM45tiQTvaTeJHTJg41Qr 1LLqP2yMC/DZt+OgAzs0SI/Ln5QbCGFnvLlacdqMCL4vRjk17KCvAbndst55x1MpaZ wnh3eSNNRDmjQvEOnCpeRq7V5jJj3ypQJFvjMyABolRWqrNyqe9GuQlDwlkKId34Th 7IdFGmYiCSFj4fk2oriLgaCWH7cdQEsbFZtIeKbAhC2cNEr80xRMzHOQU62RX0DWAP h/WxYroDRk6TA== Message-ID: <799f5069-36a1-4be7-8ee3-acb3a6cd44a2@kernel.org> Date: Sun, 21 Dec 2025 04:30:19 +0100 Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Daniel Gomez Subject: Re: [PATCH 0/2] scsi: target+fcoe: replace -EEXIST with -EBUSY in module_init() paths To: James Bottomley , "Martin K. Petersen" , Hannes Reinecke Cc: Luis Chamberlain , Petr Pavlu , Sami Tolvanen , Aaron Tomlin , Lucas De Marchi , linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org, Daniel Gomez References: <20251220-dev-module-init-eexists-linux-scsi-v1-0-5379db749d54@samsung.com> Content-Language: en-US From: Daniel Gomez Organization: kernel.org In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 20/12/2025 05.27, James Bottomley wrote: > On Sat, 2025-12-20 at 04:37 +0100, Daniel Gomez wrote: >> The error code -EEXIST is reserved by the kernel module loader to >> indicate that a module with the same name is already loaded. When a >> module's init function returns -EEXIST, kmod interprets this as >> "module already loaded" and reports success instead of failure [1]. > > That reference doesn't sufficiently explain why this error code should > be unique to modules. It's unique only to the module initialization. You can find how it's used in the kernel module code at module_patient_check_exists() in kernel/module/main.c [1]. In addition, init_module(2) man pages indicates this: man 2 init_module | grep EEXIST EEXIST A module with this name is already loaded. So, a module that is already loaded will be detected by the kernel module loader and the EEXIST error will be returned. This will be detected by kmod as success [2]. I think this functionality was added very early on in kmod by commit 5f35147 "libkmod-module: probe: add flag to stop loading on already loaded" [3]. Prior to that, module-init-tools had the same behavior [4]. Even in modutils [5], we had back then in insmod/insmod.c:2088: case EEXIST: if (dolock) { /* * Assume that we were just invoked * simultaneous with another insmod * and return success. */ exit_status = 0; goto out; } error("a module named %s already exists", m_name); goto out; Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/module/main.c?h=v6.19-rc1#n3206 [1] Link: https://github.com/kmod-project/kmod/blob/v34.2/libkmod/libkmod-module.c#L1088 [2] Link: https://github.com/kmod-project/kmod/commit/5f3514731ef82084c1a24b15445e0f1352681a19 [3] Link: https://git.kernel.org/pub/scm/utils/kernel/module-init-tools/module-init-tools.git/tree/modprobe.c#n1797 [4] Link: https://cdn.kernel.org/pub/linux/utils/kernel/modutils/v2.4/modutils-2.4.27.tar.gz [5] > EEXIST is used all over the kernel to indicate > that something being attempted has already happened or does already > exist and that seems perfectly logical .... please explain why you're That is correct but not all are conflicts within the module_init()/init_module(2) path. I have detected 40+ cases where this error is returned and another 20+ where error is returned but in upper layers of the module itself, not propagated back to userspace. So far, I've only sent just a few + docs: https://lore.kernel.org/all/20251220-dev-module-init-eexists-dm-devel-v1-1-90ed00444ea0@samsung.com https://lore.kernel.org/all/20251220-dev-module-init-eexists-keyring-v1-1-a2f23248c300@samsung.com https://lore.kernel.org/all/20251220-dev-module-init-eexists-linux-acpi-v1-1-af59b1a0e217@samsung.com https://lore.kernel.org/all/20251218-dev-module-init-eexists-modules-docs-v1-0-361569aa782a@samsung.com > trying to push it back to being a single use case for modules alone. > > Regards, > > James > > >