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Wong" , linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org, Anand Jain , dsterba@suse.com 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> Content-Language: en-US From: Anand Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 23/4/26 13:08, Christoph Hellwig wrote: > 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. Agreed. I have dropped the plan to rely on hardware identifiers; the lack of consistency in USB/NVMe firmware makes them a non-starter for a stable identifier. The updated patch set, excluding the ext4 changes, has been submitted to the mailing list. Fstests test case updated as well. Thanks, Anand