Comment 3 for bug 1860535

------- Comment From <email address hidden> 2020-01-23 02:45 EDT-------
Comment: Is the revert in LP 1846219 already sufficient to complete this ticket for Eoan? (I assume yes) Or do all the patches from LP 1830731 need to be reverted?

Answer:
No, this is not sufficient. The revert in LP 1846219 only reverts a part of the feature.
Unfortunately we have to disable the whole feature. But we would like to disable the feature instead of reverting all patches.

The patch to disable the feature is attached here

Created attachment 140187 [details]
s390/dasd: disable ese support due to possible data corruption

Devices are formatted in multiple of tracks.
For an enhanced space efficient (ese) volume we get errors when accessing
not formatted tracks. In this case the driver either formats the track
on the flight for write requests or returns zero data for read requests.

In case a request spans multiple tracks, the indication of an unformatted
track presented for the first track is incorrectly applied to all tracks
covered by the request. As a result, tracks containing data will be handled
as if empty, resulting in zero data being returned on read, or overwriting
existing data with zero on write.

While working on a proper fix disable the feature by always returning zero
for the ese check. This disables all ese special handling and prevents the
possible data corruption.