s390/dasd: Detect ESE volumes from the on-disk format label

Read the format label from track 0 record 4 at device bring-up and cache
it. When a valid label is present, is_ese() is derived from it instead of
the hardware volume field.
A volume copied off ESE storage onto other hardware is thus still handled
as thin.
Without a label (older format) is_ese() falls back to the hardware field as
before.
The cache is refreshed after a format so is_ese() stays coherent without an
offline/online cycle.

The label F_ESE bit is stamped from the hardware capability rather than
is_ese(), and space release (quick format) is gated on the hardware
capability, so a copied label cannot enable it on non-ESE hardware.

The ese sysfs attribute, and with this lsdasd, shows the hardware
capability and not the internal handling. This is in line with the view
from storage server interface. To reflect the specific internal handling an
additional attribute on_demand_formatting is added to show that a device is
handled like an ESE device internally based on the disk label.

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://patch.msgid.link/20260805111612.1285190-17-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

0 files changed, 0 insertions, 0 deletions