[paulmck-rcu:dev.2026.09.18a 24/34] block.c:undefined reference to `cmpxchg_emu_u8'

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2026.09.18a
head:   90599c372e13369d11f6c1a01ff0094b16f72cf8
commit: c98d10b438b5626edb3f4e06f4f62bcb6ed6fe90 [24/34] lib: Add two-byte cmpxchg emulation function
config: xtensa-randconfig-1000-20260929 (https://download.01.org/0day-ci/archive/20260930/202609301117.nVKrDSkb-lkp@xxxxxxxxx/config)
compiler: xtensa-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260930/202609301117.nVKrDSkb-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202609301117.nVKrDSkb-lkp@xxxxxxxxx/

All errors (new ones prefixed by >>):

   xtensa-linux-ld: fs/crypto/block.o: in function `fscrypt_limit_io_blocks':
>> block.c:(.text+0x300): undefined reference to `cmpxchg_emu_u8'
   xtensa-linux-ld: fs/crypto/block.o: in function `fscrypt_zeroout_range_end_io':
   block.c:(.text+0x31c): undefined reference to `cmpxchg_emu_u8'
   xtensa-linux-ld: fs/btrfs/bio.o: in function `btrfs_bio_alloc':
>> bio.c:(.text+0x88c): undefined reference to `cmpxchg_emu_u8'
   xtensa-linux-ld: fs/btrfs/bio.o: in function `btrfs_bio_end_io':
   bio.c:(.text+0x8e8): undefined reference to `cmpxchg_emu_u8'
   `.exit.text' referenced in section `__jump_table' of drivers/staging/vme_user/vme_fake.o: defined in discarded section `.exit.text' of drivers/staging/vme_user/vme_fake.o
   `.exit.text' referenced in section `__jump_table' of drivers/staging/vme_user/vme_fake.o: defined in discarded section `.exit.text' of drivers/staging/vme_user/vme_fake.o
   xtensa-linux-ld: block/blk-crypto-fallback.o: in function `blk_crypto_fallback_decrypt_endio':
>> blk-crypto-fallback.c:(.text+0x10c): undefined reference to `cmpxchg_emu_u8'
   xtensa-linux-ld: block/blk-crypto-fallback.o:blk-crypto-fallback.c:(.text+0x18c): more undefined references to `cmpxchg_emu_u8' follow

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