I'm (unsurprisingly) experiencing the same problem on sid. This appears to be the relevant section of the make.log
CC [M] /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/rx_kmutex.o In file included from /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/rx_kmutex.c:24: /var/lib/dkms/openafs/1.8.6/build/src/afs/LINUX/osi_compat.h: In function ‘kernel_setsockopt’: /var/lib/dkms/openafs/1.8.6/build/src/afs/LINUX/osi_compat.h:326:12: error: implicit declaration of function ‘get_ds’; did you mean ‘get_fs’? [-Werror=implicit-function-declaration] 326 | set_fs(get_ds()); | ^~~~~~ | get_fs /var/lib/dkms/openafs/1.8.6/build/src/afs/LINUX/osi_compat.h:326:12: error: incompatible type for argument 1 of ‘set_fs’ 326 | set_fs(get_ds()); | ^~~~~~~~ | | | int In file included from /usr/src/linux-headers-5.8.0-1-common/include/linux/uaccess.h:11, from /usr/src/linux-headers-5.8.0-1-common/include/linux/crypto.h:21, from /usr/src/linux-headers-5.8.0-1-common/include/crypto/hash.h:11, from /usr/src/linux-headers-5.8.0-1-common/include/linux/uio.h:10, from /usr/src/linux-headers-5.8.0-1-common/include/linux/socket.h:8, from /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/./h/socket.h:1, from /var/lib/dkms/openafs/1.8.6/build/src/rx/rx_kcommon.h:51, from /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/rx_kmutex.c:20: /usr/src/linux-headers-5.8.0-1-common/arch/x86/include/asm/uaccess.h:29:40: note: expected ‘mm_segment_t’ but argument is of type ‘int’ 29 | static inline void set_fs(mm_segment_t fs) | ~~~~~~~~~~~~~^~ In file included from /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/rx_kmutex.c:24: /var/lib/dkms/openafs/1.8.6/build/src/afs/LINUX/osi_compat.h: In function ‘kernel_getsockopt’: /var/lib/dkms/openafs/1.8.6/build/src/afs/LINUX/osi_compat.h:339:12: error: incompatible type for argument 1 of ‘set_fs’ 339 | set_fs(get_ds()); | ^~~~~~~~ | | | int In file included from /usr/src/linux-headers-5.8.0-1-common/include/linux/uaccess.h:11, from /usr/src/linux-headers-5.8.0-1-common/include/linux/crypto.h:21, from /usr/src/linux-headers-5.8.0-1-common/include/crypto/hash.h:11, from /usr/src/linux-headers-5.8.0-1-common/include/linux/uio.h:10, from /usr/src/linux-headers-5.8.0-1-common/include/linux/socket.h:8, from /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/./h/socket.h:1, from /var/lib/dkms/openafs/1.8.6/build/src/rx/rx_kcommon.h:51, from /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/rx_kmutex.c:20: /usr/src/linux-headers-5.8.0-1-common/arch/x86/include/asm/uaccess.h:29:40: note: expected ‘mm_segment_t’ but argument is of type ‘int’ 29 | static inline void set_fs(mm_segment_t fs) | ~~~~~~~~~~~~~^~ cc1: some warnings being treated as errors make[5]: *** [/usr/src/linux-headers-5.8.0-1-common/scripts/Makefile.build:286: /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP/rx_kmutex.o] Error 1 make[4]: *** [/usr/src/linux-headers-5.8.0-1-common/Makefile:1768: /var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP] Error 2 make[3]: *** [/usr/src/linux-headers-5.8.0-1-common/Makefile:185: __sub-make] Error 2 make[3]: Leaving directory '/usr/src/linux-headers-5.8.0-1-amd64' FAILURE: make exit code 2 make[2]: *** [Makefile.afs:279: openafs.ko] Error 1 make[2]: Leaving directory '/var/lib/dkms/openafs/1.8.6/build/src/libafs/MODLOAD-5.8.0-1-amd64-SP' make[1]: *** [Makefile:186: linux_compdirs] Error 2 make[1]: Leaving directory '/var/lib/dkms/openafs/1.8.6/build/src/libafs' make: *** [Makefile:15: all] Error 2