PROBLEM: 5.9.0-rc6 fails to compile due to 'redefinition of ‘dax_supported’'

[Stuart Little]

I am trying to compile for an x86_64 machine (Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz). The config file I am currently using is at

https://termbin.com/xin7

The build for 5.9.0-rc6 fails with the following errors:

--- cut here ---

drivers/dax/super.c:325:6: error: redefinition of ‘dax_supported’
  325 | bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev,
      |      ^~~~~~~~~~~~~
In file included from drivers/dax/super.c:16:
./include/linux/dax.h:162:20: note: previous definition of ‘dax_supported’ was here
  162 | static inline bool dax_supported(struct dax_device *dax_dev,
      |                    ^~~~~~~~~~~~~
  CC      lib/memregion.o
  CC [M]  drivers/gpu/drm/drm_gem_vram_helper.o
make[2]: *** [scripts/Makefile.build:283: drivers/dax/super.o] Error 1
make[1]: *** [scripts/Makefile.build:500: drivers/dax] Error 2
make[1]: *** Waiting for unfinished jobs....

--- end ---

That's earlier on, and then later, at the end of the (failed) build:

make: *** [Makefile:1784: drivers] Error 2

The full build log is at

https://termbin.com/ihxj

but I do not see anything else amiss. 5.9.0-rc5 built fine last week.