read(2) failed: Read-only file system

[Paul Ripke <stix%stix.id.au@localhost>]

So I have a dying disk (WD20EARX) in a USB enclosure, and I tried to
do some random reads against the raw device:

read I/O failed, offset 363065167872: 30 (Read-only file system)

I guess I'm a little surprised by this error?
Nor does read(2) list EROFS as a possible return, which seems sensible.

Looking at the code, I'm guessing the drive is returning
SKEY_DATA_PROTECT for some reason, so this is likely not a bug, but
interesting behaviour.

Indeed:

Jun 27 16:19:40 slave /netbsd: [ 3710565.0174648] sd0(umass0:0:0:0):  Check Condition on CDB: 0x28 00 2a 44 2f 68 00 00 08 00
Jun 27 16:19:40 slave /netbsd: [ 3710565.0174648]     SENSE KEY:  Write Protected
Jun 27 16:19:40 slave /netbsd: [ 3710565.0174648]      ASC/ASCQ:  Logical Unit Access Not Authorized
Jun 27 16:19:40 slave /netbsd: [ 3710565.0174648] sd0d: error reading fsbn 709111656 of 709111656-709111663 (sd0 bn 709111656; cn 346245 tn 59 sn 8)

So, yeah. This is such an edge case it's probably not even worth
documenting beyond this email?

NetBSD 9.2, amd64, fwiw.

-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.