From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 3FE7321E098; Thu, 23 Apr 2026 05:08:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776920914; cv=none; b=gmlxPFjvQqQw5wHsmyxNS7lUerD+625mK4r0h76L59AaNZsf5idc0OOpmRzZTRgDoGrQR+Qq5DKXyQ41+q+sg/m4xlA1gK88mBpw2bMhJxkS3/oaXmf9hHOtl0DCpyY+Su6PdXHaKBtDG6GfLxwZswovTYNtiwUrwjxV5AwD710= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776920914; c=relaxed/simple; bh=HrfNR7fnumiB56vEYMy3p40je4xEW7wwiAn4IjvsHko=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KmEL7FLT5Klz5hi1C8qcoFKIfiDvGQSqq37yUfPyCpiHw3QQUMQPSbfhGAdEriUCjvQUpP2OZ+n/bLJ4IALWtCEegqh0qdajd30cBBlM8Gi6poLwuKLOE0ou2X/DyjNVUPSdDrhk+j89kGqiFMbsEhfoTXJwQjPByLN24sIH+e4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=FYv33qok; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="FYv33qok" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=1OxXqEnjl+54GOy6xnGRl8Qec/72RctUzHC5EckBAQk=; b=FYv33qokR6WpAV/RxGOQbhG8YO wmLSRqHLiTV3pezvTYS6WBzXykW/GPGgHRYwb4aPcgRqyc+6UlaQpy7TMpy1ZowpTR91JlBPZuh2+ iUDEMyQC+jdsob+ZwUweKrrniV2nVCt1NILstuFWH2RVgSfT5f/UqdIjSbAIRy6sMaqrae5fUPtiZ ZzgU/U2ppSgJ87aIbWc2dvTRlDwbSeVN2wG0wJgFfDYON4fm10aZrWJX9h9H/uWRp63ap5iMgdMLG XOKWNt07GQaAzAGH458GgeePKU7+dCR41p4Umn1ufD+S6ceHUXcTbj2ApQPcD71YvHKuhmWxk2z04 8lqyZJxg==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1wFmIf-0000000B3C9-0TS1; Thu, 23 Apr 2026 05:08:29 +0000 Date: Wed, 22 Apr 2026 22:08:29 -0700 From: Christoph Hellwig To: Anand Jain Cc: Christoph Hellwig , Theodore Tso , "Darrick J. Wong" , linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org, Anand Jain , dsterba@suse.com Subject: Re: [PATCH v2 3/3] ext4: derive f_fsid from block device to avoid collisions Message-ID: References: <5bda3d00-df35-4ea1-b313-2fef6e5c5682@gmail.com> <20260407144709.GA81690@macsyma-wired.lan> <3c9e478a-42ef-446f-a8cc-1b4ac970d2ef@gmail.com> <20260409041035.GC99725@macsyma-wired.lan> <22cfbf8d-af9b-462e-b240-67a1de24764f@gmail.com> <20260409131238.GC18443@macsyma-wired.lan> Precedence: bulk X-Mailing-List: linux-xfs@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: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Wed, Apr 22, 2026 at 07:39:57PM +0800, Anand Jain wrote: > > No, T10 does not actually mandate unique identifiers, NVMe does, but the > > implementations are often totally broken. > > Right. Newer SPC-3 (and above) compliant devices must support > the Inquiry CDB EVPD flag and provide page 0x83 for identification, > which is what we typically use for multipathing. But there is no requirement for it to contain something useful. > These are globally unique. And, we can overlook legacy > drives, as they've probably been past their EOSL for a while now. We have absolutely no useful identifiers for most USB devices. NVMe devices have broken identifiers all the time as well. So no, you can't.