Hi Sergei,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.9-rc7]
[cannot apply to block/for-next sparc-next/master next-20201002]
[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/Sergei-Shtepa/Block-snapshot-module-and-block-layer-filter-API/20201002-210406
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 472e5b056f000a778abb41f1e443de58eb259783
config: sparc-allyesconfig (attached as .config)
compiler: sparc64-linux-gcc (GCC) 9.3.0
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/61a37e3bb74afbef1b725eaf80405e0e6e5d64b7
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Sergei-Shtepa/Block-snapshot-module-and-block-layer-filter-API/20201002-210406
        git checkout 61a37e3bb74afbef1b725eaf80405e0e6e5d64b7
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=sparc 

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

All error/warnings (new ones prefixed by >>):

   drivers/block/blk-snap/snapstore_mem.c: In function 'snapstore_mem_destroy':
>> drivers/block/blk-snap/snapstore_mem.c:48:4: error: implicit declaration of function 'vfree'; did you mean 'kvfree'? [-Werror=implicit-function-declaration]
      48 |    vfree(buffer_el->buff);
         |    ^~~~~
         |    kvfree
   drivers/block/blk-snap/snapstore_mem.c: In function 'snapstore_mem_get_block':
>> drivers/block/blk-snap/snapstore_mem.c:74:20: error: implicit declaration of function '__vmalloc'; did you mean '__kmalloc'? [-Werror=implicit-function-declaration]
      74 |  buffer_el->buff = __vmalloc(snapstore_block_size() * SECTOR_SIZE, GFP_NOIO);
         |                    ^~~~~~~~~
         |                    __kmalloc
>> drivers/block/blk-snap/snapstore_mem.c:74:18: warning: assignment to 'void *' from 'int' makes pointer from integer without a cast [-Wint-conversion]
      74 |  buffer_el->buff = __vmalloc(snapstore_block_size() * SECTOR_SIZE, GFP_NOIO);
         |                  ^
   cc1: some warnings being treated as errors

vim +48 drivers/block/blk-snap/snapstore_mem.c

    28	
    29	void snapstore_mem_destroy(struct snapstore_mem *mem)
    30	{
    31		struct buffer_el *buffer_el;
    32	
    33		if (mem == NULL)
    34			return;
    35	
    36		do {
    37			buffer_el = NULL;
    38	
    39			mutex_lock(&mem->blocks_lock);
    40			if (!list_empty(&mem->blocks)) {
    41				buffer_el = list_entry(mem->blocks.next, struct buffer_el, link);
    42	
    43				list_del(&buffer_el->link);
    44			}
    45			mutex_unlock(&mem->blocks_lock);
    46	
    47			if (buffer_el) {
  > 48				vfree(buffer_el->buff);
    49				kfree(buffer_el);
    50			}
    51		} while (buffer_el);
    52	
    53		blk_descr_mem_pool_done(&mem->pool);
    54	
    55		kfree(mem);
    56	}
    57	
    58	void *snapstore_mem_get_block(struct snapstore_mem *mem)
    59	{
    60		struct buffer_el *buffer_el;
    61	
    62		if (mem->blocks_allocated >= mem->blocks_limit) {
    63			pr_err("Unable to get block from snapstore in memory\n");
    64			pr_err("Block limit is reached, allocated %ld, limit %ld\n", mem->blocks_allocated,
    65			       mem->blocks_limit);
    66			return NULL;
    67		}
    68	
    69		buffer_el = kzalloc(sizeof(struct buffer_el), GFP_KERNEL);
    70		if (buffer_el == NULL)
    71			return NULL;
    72		INIT_LIST_HEAD(&buffer_el->link);
    73	
  > 74		buffer_el->buff = __vmalloc(snapstore_block_size() * SECTOR_SIZE, GFP_NOIO);

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