dm dust: make badblock messages target-relative

dm-dust currently treats addbadblock, removebadblock and queryblock
arguments as block numbers on the underlying device. That is surprising
for a device-mapper target: a dm-dust table with a non-zero backing
offset can add bad blocks that are outside the mapped target, and a
badblock added for logical block 0 is missed because the I/O path checks
the remapped backing-device block instead.

Interpret badblock message arguments as blocks relative to the start of
the dm-dust target instead. Bound the arguments by the target length and
perform badblock lookup using target-relative sectors before remapping
the bio to the underlying device.

This intentionally changes the non-zero backing-offset behavior to make
the badblock control interface match the mapped dm-dust device, rather
than the underlying device.

Assisted-by: Codex:gpt-5.5-cyber-preview
Signed-off-by: Samuel Moelius <sam.moelius@trailofbits.com>
Tested-by: Bryan Gurney <bgurney@redhat.com>
Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

0 files changed, 0 insertions, 0 deletions