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Date:   Wed, 12 Jul 2023 10:38:40 +0300
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Subject: Re: Fwd: Need NVME QUIRK BOGUS for SAMSUNG MZ1WV480HCGL-000MV
 (Samsung SM-953 Datacenter SSD)
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To:     Keith Busch <kbusch@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Christoph Hellwig <hch@lst.de>,
        Linux regressions mailing list <regressions@lists.linux.dev>,
        Pankaj Raghav <p.raghav@samsung.com>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Jens Axboe <axboe@kernel.dk>,
        "Clemens S." <cspringsguth@gmail.com>,
        Martin Belanger <martin.belanger@dell.com>,
        Chaitanya Kulkarni <kch@nvidia.com>,
        John Meneghini <jmeneghi@redhat.com>,
        Hannes Reinecke <hare@suse.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux NVMe <linux-nvme@lists.infradead.org>,
        Kanchan Joshi <joshi.k@samsung.com>,
        Javier Gonzalez <javier.gonz@samsung.com>,
        =?UTF-8?B?67CV7KeE7ZmY?= <jh.i.park@samsung.com>
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From:   Sagi Grimberg <sagi@grimberg.me>
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>> For example, we have this completely unacceptable garbage:
>>
>>          ret = nvme_global_check_duplicate_ids(ctrl->subsys, &info->ids);
>>          if (ret) {
>>                  dev_err(ctrl->device,
>>                          "globally duplicate IDs for nsid %d\n", info->nsid);
>>                  nvme_print_device_info(ctrl);
>>                  return ret;
>>          }
>>
>> iow, the code even checks for and *notices* that there are duplicate
>> IDs, and what does it do? It then errors out.
> 
> This check came from a recent half-baked spec feature called "Dispersed
> Namespaces" that caused breakage and data corruption when used in Linux.
> Rather than attempt to support that mostly vendor specific feature, the
> driver attempted to fence that off as unmaintainable. This check wasn't
> aimed at enforcing "correctness", but it certainly found a lot of that
> as collatoral damage. Let's see if we can find a better way to detect
> the difference with a sane fallback as you suggest.

Perhaps we could fallback to what we do in wwid_show()?

"nvme.%04x-%*phN-%*phN-%08x\n", subsys->vendor_id, serial_len,
subsys->serial, model_len, subsys->model, head->ns_id)