Hi, I tried to add some support for using devices with PI/DIF metadata and checked (through sysfs) how large metadata space per sector is available.
The problem is that some values behave differently than I expected. For an NVMe drive, reformatted to 4096 + 64 profile, I see this: - /sys/block/<disk>/integrity/device_is_integrity_capable Contains 0 (?) According to docs, this field "Indicates whether a storage device is capable of storing integrity metadata. Set if the device is T10 PI-capable." - /sys/block/<disk>/integrity/format Contains expected "nop" (not "none") - /sys/block/<disk>/integrity/tag_size Contains 0 (?) According to docs, this is "Number of bytes of integrity tag space available per 512 bytes of data." (I think 512 bytes is incorrect; it should be sector size, or perhaps value in protection_interval_bytes, though.) Then we have new (undocumented) value for NVMe in - /sys/block/<nvme>/integrity/metadata_bytes This contains the correct 64. Anyway, when I try to use it (for authentication tags in dm-crypt), it works. Should tag_size and device_is_integrity_capable be set even for the "nop" format? Is it a bug or a feature? :-) If not, what is the correct way to read per-sector metadata size (not only for NVMe as metadata_bytes is not available for other block devices)? (This is on recent Linus' master - 6.14.0-rc4) Thanks, Milan
