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811f4de034
Currently, if nvme_scan_ns_list fails, nvme_scan_work will fall back to a sequential scan. nvme_scan_ns_list can fail for a variety of reasons, e.g. a transient transport issue, and the resulting sequential scan can be extremely expensive on controllers reporting an NN value close to the maximum allowed (> 4 billion). Avoid sequential scans wherever possible by only falling back to them in two cases: - When the NVMe version supported (VS) value reported by the device is older than NVME_VS(1, 1, 0), before which support of Identify NS List not required. - When the Identify NS List command fails with the DNR bit set in the status. This is to accommodate (non-compliant) devices which report a VS value which implies support for Identify NS List, but nevertheless do not support the command. Such devices will most likely fail the command with the DNR bit set. The third case is when the device claims support for Identify NS List but the command fails with DNR not set. In such cases, fallback to sequential scan is potentially expensive and likely unnecessary, as a retry of the list scan should succeed. So this change skips the fallback in this third case. Signed-off-by: Uday Shankar <ushankar@purestorage.com> Signed-off-by: Christoph Hellwig <hch@lst.de> |
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