TLDR
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Linus Torvalds traced a 30-second USB mount delay to blkid issuing a 68kB read against a 16kB/s embroidery machine storage device.
Key Takeaways
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blkid -p on both /dev/sdc and /dev/sdc1 consumed 27+ seconds total, dominated by a single 69632-byte read triggering kernel read-ahead to ~120kB.
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devkit-disks-part-id extracted the same partition metadata far faster, suggesting udev should call it first and skip blkid entirely.
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Scanning the whole disk
/dev/sdc before the partition /dev/sdc1 is redundant; the kernel already partitioned it.
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Devices without a UUID are silently not mounted by hald, leaving no user-visible error and no workaround for locked firmware.
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The fix Torvalds wanted: skip blkid in udev rules, improve blkid read sizing, and allow UUID-less automount.
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