Re: [dm-devel] [PATCH v2] dm table: simplify discard support processing

[Mike Snitzer <snitzer redhat com>]

Updated patch header to also point out the fix:

Remove 'discards_supported' from the dm_table structure.  The same
information can be easily discovered from the table's target(s) in
dm_table_supports_discards().

This change fixes an issue with per-target 'discards_supported' being
ineffective, at insuring the final DM device advertises discard support,
due to a different target not having 'num_discard_requests' > 0 -- this
resulted in the overall table's 'discards_supported' being set to 0.

Also DMWARN if a target sets 'discards_supported' override but forgets
to set 'num_discard_requests'.