Hi Luis,

I love your patch! Yet something to improve:

[auto build test ERROR on block/for-next]
[also build test ERROR on v5.12-rc8 next-20210423]
[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/Luis-Chamberlain/zram-fix-few-sysfs-races/20210423-091311
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
config: x86_64-rhel-8.3-kselftests (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/f5a504c4eb54fd32acdbb779e3ede281f3039a5a
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Luis-Chamberlain/zram-fix-few-sysfs-races/20210423-091311
        git checkout f5a504c4eb54fd32acdbb779e3ede281f3039a5a
        # save the attached .config to linux build tree
        make W=1 W=1 ARCH=x86_64 

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

All errors (new ones prefixed by >>):

   drivers/block/zram/zram_drv.c: In function 'writeback_limit_enable_show':
>> drivers/block/zram/zram_drv.c:451:3: error: 'len' undeclared (first use in this function)
     451 |   len = -ENODEV;
         |   ^~~
   drivers/block/zram/zram_drv.c:451:3: note: each undeclared identifier is reported only once for each function it appears in
   drivers/block/zram/zram_drv.c:469:1: error: control reaches end of non-void function [-Werror=return-type]
     469 | }
         | ^
   cc1: some warnings being treated as errors


vim +/len +451 drivers/block/zram/zram_drv.c

   440	
   441	static ssize_t writeback_limit_enable_show(struct device *dev,
   442			struct device_attribute *attr, char *buf)
   443	{
   444		bool val;
   445		struct zram *zram;
   446	
   447		if (!try_module_get(THIS_MODULE))
   448			return -ENODEV;
   449	
   450		if (!bdgrab(dev_to_bdev(dev))) {
 > 451			len = -ENODEV;
   452			goto out_nodev;
   453		}
   454	
   455		zram = dev_to_zram(dev);
   456	
   457		down_read(&zram->init_lock);
   458		spin_lock(&zram->wb_limit_lock);
   459		val = zram->wb_limit_enable;
   460		spin_unlock(&zram->wb_limit_lock);
   461		up_read(&zram->init_lock);
   462		len = scnprintf(buf, PAGE_SIZE, "%d\n", val);
   463	
   464		bdput(dev_to_bdev(dev));
   465	out_nodev:
   466		module_put(THIS_MODULE);
   467	
   468		return len;
   469	}
   470	

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