sbull.c: implicit declaration of function blk_alloc_queue against kernel version 5.14.9

[QuantumForge]

sbull.c fails to compile due to missing reference to blk_alloc_queue:

make[2]: Entering directory '/home/whanlon/kernelbuild/linux-5.14.9'
  CC [M]  /home/whanlon/LinuxDeviceDrivers/examples/ldd3/sbull/sbull.o
/home/whanlon/LinuxDeviceDrivers/examples/ldd3/sbull/sbull.c: In function 'blk_generic_alloc_queue':
/home/whanlon/LinuxDeviceDrivers/examples/ldd3/sbull/sbull.c:110:17: error: implicit declaration of function 'blk_alloc_queue'; did you mean 'blk_sync_queue'? [-Werror=implicit-function-declaration]
  110 |         return (blk_alloc_queue(node_id));
      |                 ^~~~~~~~~~~~~~~
      |                 blk_sync_queue
/home/whanlon/LinuxDeviceDrivers/examples/ldd3/sbull/sbull.c:110:17: warning: returning 'int' from a function with return type 'struct request_queue *' makes pointer from integer without a cast [-Wint-conversion]
  110 |         return (blk_alloc_queue(node_id));
      |                ~^~~~~~~~~~~~~~~~~~~~~~~~~

This is followed by a cascade of other errors, the end result is "make" fails when trying to compile sbull.c

Looking in the kernel source I find blk_alloc_queue in block/blk-core.c, but nowhere in linux-5.14.9/include. I also notice that blk_alloc_queue in blk-core.c is not followed by EXPORT_SYMBOL. Is this function deprecated in 5.14+ kernels? How to fix this to get ldd3 to compile?

[dwalkes]

See https://stackoverflow.com/questions/60275288/implicit-declaration-of-blk-init-queue and https://prog.world/linux-kernel-5-0-we-write-simple-block-device-under-blk-mq/

Looks like we need to move to blk_mq_init_queue