Pull UML updates from Richard Weinberger:
- DISCARD support for our block device driver
- Many TLB flush optimizations
- Various smaller fixes
- And most important, Anton agreed to help me maintaining UML
* 'for-linus-4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
um: Remove obsolete reenable_XX calls
um: writev needs <sys/uio.h>
Add Anton Ivanov to UML maintainers
um: remove redundant generic-y
um: Optimize Flush TLB for force/fork case
um: Avoid marking pages with "changed protection"
um: Skip TLB flushing where not needed
um: Optimize TLB operations v2
um: Remove unnecessary faulted check in uaccess.c
um: Add support for DISCARD in the UBD Driver
um: Remove unsafe printks from the io thread
um: Clean-up command processing in UML UBD driver
um: Switch to block-mq constants in the UML UBD driver
um: Make GCOV depend on !KCOV
um: Include sys/uio.h to have writev()
um: Add HAVE_DEBUG_BUGVERBOSE
um: Update maintainers file entry
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