Hi John,

I love your patch! Perhaps something to improve:

[auto build test WARNING on block/for-next]
[also build test WARNING on v5.14-rc5 next-20210809]
[cannot apply to mkp-scsi/for-next ceph-client/for-linus scsi/for-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/John-Garry/blk-mq-Reduce-static-requests-memory-footprint-for-shared-sbitmap/20210809-223943
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
config: hexagon-randconfig-r036-20210809 (attached as .config)
compiler: clang version 12.0.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/535293cab26a196d29b64d9ce8a7274bfd1806d8
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review John-Garry/blk-mq-Reduce-static-requests-memory-footprint-for-shared-sbitmap/20210809-223943
        git checkout 535293cab26a196d29b64d9ce8a7274bfd1806d8
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=hexagon 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> block/blk-mq.c:2313:6: warning: no previous prototype for function 'blk_mq_clear_rq_mapping' [-Wmissing-prototypes]
   void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
        ^
   block/blk-mq.c:2313:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
   ^
   static 
   1 warning generated.


vim +/blk_mq_clear_rq_mapping +2313 block/blk-mq.c

  2311	
  2312	/* called before freeing request pool in @tags */
> 2313	void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
  2314				     struct blk_mq_tags *tags)
  2315	{
  2316		struct page *page;
  2317		unsigned long flags;
  2318	
  2319		list_for_each_entry(page, &tags->page_list, lru) {
  2320			unsigned long start = (unsigned long)page_address(page);
  2321			unsigned long end = start + order_to_size(page->private);
  2322			int i;
  2323	
  2324			for (i = 0; i < drv_tags->nr_tags; i++) {
  2325				struct request *rq = drv_tags->rqs[i];
  2326				unsigned long rq_addr = (unsigned long)rq;
  2327	
  2328				if (rq_addr >= start && rq_addr < end) {
  2329					WARN_ON_ONCE(refcount_read(&rq->ref) != 0);
  2330					cmpxchg(&drv_tags->rqs[i], rq, NULL);
  2331				}
  2332			}
  2333		}
  2334	
  2335		/*
  2336		 * Wait until all pending iteration is done.
  2337		 *
  2338		 * Request reference is cleared and it is guaranteed to be observed
  2339		 * after the ->lock is released.
  2340		 */
  2341		spin_lock_irqsave(&drv_tags->lock, flags);
  2342		spin_unlock_irqrestore(&drv_tags->lock, flags);
  2343	}
  2344	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org