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 739BB45FFDC for ; Mon, 14 Sep 2026 12:28:15 +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=1789388896; cv=none; b=QDKZLA/W4kpiJpFcKY/FJA+CUe9tHbZtVH0M1DtU5zbFaGdezaD9n8tRRspzu8i66ke041wpg6dafcL6u3ake5dp1UdgaVkA9TQFVRGYLByzSLu6dw92pdcqWKjZVptJ9WLc3SRR9REgY569tCy2/POU0jziKd1Xq5JexZFUfYY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789388896; c=relaxed/simple; bh=KIcJWp2l8aBpcwfXDmcPkwoC91TRFDdqgyWuaPmjioU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jApK3AaUiBgOphgvnst7UHbBFRnMfxNzHzXs5nJvRzfdYZMlTjpiV4GGeRC1tWwA+QJX+lOAx9KYv94GcQ83Cean+upz/LTyVkwokCQDLGNBFZW3kGfBSK2Xyg+7AAzQ1g2MRW8LJGnpMWivk/C3ntB7YI1t+dtusSs1MudrTPE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hLx7tVPR; 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="hLx7tVPR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 399261F000FF; Mon, 14 Sep 2026 12:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789388895; bh=KIcJWp2l8aBpcwfXDmcPkwoC91TRFDdqgyWuaPmjioU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hLx7tVPRCZ3qyOX7P1luZNza8zPx8XW6MTWVFS2oXPQ+lThEOwpFxmCm64KnhYtNu gyRJQXWHU/wL7kSu1y3c2SMJo1yTRrYVw7tEzw/FmBBMYZEt+yWL+KHx3qmVJjK5D/ C4dCLtXFGbS2rYjYhdjDiLWtn0VpZVVMTT258wCd6fggo1Dz4GxW7X0CL2XqylOInx 68BF6bsoSUcKrvuUQB70EcNV1L5P+TlHZA0Tbvd7TdUlVKrIlUMN44Nxdw/Ad4aCcR d4l/VeEvj+SFJYqLHoaWLiDJ07kla7Sfm7KZnIbZ2vbU/M22Ongfw26QgTwAPNiTVX zdYKW7z0gSasQ== Message-ID: <6e78fa81-3bc1-4821-b41c-5c18d9fe8a53@kernel.org> Date: Mon, 14 Sep 2026 20:28:12 +0800 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: derive f_fsid with dev_t only when temp_fsid is active To: David Woodhouse , dsterba@suse.cz, linux-btrfs@vger.kernel.org Cc: thiago.macieira@intel.com, dave.hansen@intel.com References: <16069a6fc651168bfcd2394d6e57ce63a50231ed.1789235482.git.asj@kernel.org> <0691a903-cc82-4ad7-8264-cddbf146d00e@kernel.org> <91E0EA5B-BFD2-4B8A-8408-4F561D5E0777@infradead.org> Content-Language: en-US From: Anand Suveer Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit > The documentation is fairly poor, but historical > behaviour and expectation is that the FSID is supposed to be *stable*. It's definitely messy. Statfs f_fsid was never strictly guaranteed to be persistent across reboots when derived from dev_t, filesystems like XFS and F2FS share the same design. Historically, the documentation around f_fsid has been ambiguous, leading to different expectations across filesystems. Breaking tools that rely on a stable {fsid, ino} is a real problem. The idea with this patch is to restore the original behavior as the default, and an option to mix in dev_t when needed to avoid collisions.