linuxkpi: Add mmap_lock.h

[manu]

Summary

This contain mmap_read_lock, mmap_read_unlock and mmap_write_lock_killable
which are abstraction around down_read, up_read and down_write_killable.
Note that in Linux 5.8 mmap_sem was renamed to mmap_lock.
We might want to do the same at some point but some drivers still uses
the old mmap locking API.

MFC after: 2 weeks
Sponsored by: Beckhoff Automation GmbH & Co. KG

[wulf]

sys/compat/linuxkpi/common/include/linux/mm_types.h

48

Can anonymous union be used to handle both names?

[manu]

sys/compat/linuxkpi/common/include/linux/mm_types.h

48

Probably yes but using the new API I think that you're not supposed to use or know the underlying name.

[bz]

Otherwise looks okay to me.

sys/compat/linuxkpi/common/include/linux/mmap_lock.h

29

{{{
#include <linux/mm_types.h>
#include <linux/rwsem.h>
}}}