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 3E352376BD0 for ; Mon, 27 Jul 2026 14:24:41 +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=1785162283; cv=none; b=r55y1odSP2HEBOQqjI6RXa8SKb2l1bZrshQGeV+ZVnE8+oVyxBqkapMbtfVkglhsL77KCPeQqBnyql5pFc4Lrmb95tEq6GIVf6ZuAa3KfX/T80x7s+g0VuUDcbCjn4lkPIbZm/AsHOwKijpNKfT7cG+VPdBXJadCP6txOKagt+g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785162283; c=relaxed/simple; bh=O9BSCW6AJKwjlqN7+2OZAbb6RXa1KPqOW/HKiQLl1t8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=MhNJLxL2jCkU4fWnyrUSC9EkVjFpaxxRZmJm696X5jPrbOjMjx7L8YCcoL5D3e/h2EYtTFJMJ6zoaK0L48ZkUtTtTmIf7cRkwrKA7Np7I8e97ZoRj9Sl05F8VxB32CIPb/FV9wg4AuW0EVr50Z5ZIrIqejJauYN2d4O88rqj/Kk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UUUjzyw0; 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="UUUjzyw0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7ABBC1F000E9; Mon, 27 Jul 2026 14:24:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785162281; bh=BhY9/KraQUCSXM1kTBMLeBmHA+bbILbhXU+6O9/0rFw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=UUUjzyw0sVoo3QEs4Qa+UOjw54f/gV3ku3GbccoJ1eGg4z3TmwScj+3FEBmuwx6/t 9Tqx00yNtPP9j4u2my3Oer3Jpx8aW3PAZxBMGrmarDLjj4OjRNFuQaQdLzdZMtKkNK 9n2BP4327l1NAmDSRJPim9ITKT3SN3rwrCzaRO5YEvOWIWa8iPLmR1gfmuNzJ7Bshb 8Ftu/ePcxnx5SWBz/BSJhGRoxkBPw92CrmlKEzrEIO43zIMKUrtwTpnX4kketcBtC8 hHUBDjZgPJrL65iQw/lv/LJWY19boKGFoajtqAfLZ+NbHPZMUSk5+oXSWrRXbfwyKC WOi1fWaP8HQIQ== Date: Mon, 27 Jul 2026 08:24:40 -0600 From: Keith Busch To: Hari Mishal Cc: Jens Axboe , Christoph Hellwig , Sagi Grimberg , Hannes Reinecke , Kanchan Joshi , Nitesh Shetty , Greg Kroah-Hartman , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] nvme: drop WARN_ON_ONCE on write_stream bounds check Message-ID: References: <20260725135111.14041-1-harimishal1@gmail.com> <20260725135111.14041-3-harimishal1@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260725135111.14041-3-harimishal1@gmail.com> On Sat, Jul 25, 2026 at 03:51:11PM +0200, Hari Mishal wrote: > write_stream is validated against bdev_max_write_streams() in both > generic block direct I/O (block/fops.c) and F2FS before a bio > carrying it is ever built, so write_stream > nr_plids shouldn't be > reachable through any current legitimate path. The remaining users > of bio->bi_write_stream elsewhere in the block layer only copy an > already-validated value between bios (bio.c, blk-crypto-fallback.c) > or compare it for merge eligibility (blk-merge.c); none of them > introduce a new, unvalidated value. > > Using WARN_ON_ONCE as the backstop for that assumption isn't worth > it given how many deployed systems run with panic-on-warn enabled; > the existing graceful return BLK_STS_INVAL already handles it on > its own. That's not a very good reason to remove a WARN_ON. You've left the check in for a condition that should never happen, so when it does happen, it'll be impossible to debug without the WARN. And the WARN also annotates the branch as unlikely, which is desirable for this case.