Hi Shaohua,

[auto build test ERROR on linus/master]
[also build test ERROR on v4.12-rc5]
[cannot apply to driver-core/driver-core-testing block/for-next next-20170615]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Shaohua-Li/kernfs-implement-i_generation/20170615-211524
config: x86_64-randconfig-x014-201724 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   block/bfq-cgroup.c: In function 'bfq_bic_update_cgroup':
>> block/bfq-cgroup.c:679:2: error: implicit declaration of function 'blkg_path' [-Werror=implicit-function-declaration]
     blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path));
     ^~~~~~~~~
   cc1: some warnings being treated as errors

vim +/blkg_path +679 block/bfq-cgroup.c

8f9bebc3 Paolo Valente 2017-06-05  673  	 * Finally, note that bfqg itself needs to be protected from
8f9bebc3 Paolo Valente 2017-06-05  674  	 * destruction on the blkg_free of the original blkg (which
8f9bebc3 Paolo Valente 2017-06-05  675  	 * invokes bfq_pd_free). We use an additional private
8f9bebc3 Paolo Valente 2017-06-05  676  	 * refcounter for bfqg, to let it disappear only after no
8f9bebc3 Paolo Valente 2017-06-05  677  	 * bfq_queue refers to it any longer.
8f9bebc3 Paolo Valente 2017-06-05  678  	 */
8f9bebc3 Paolo Valente 2017-06-05 @679  	blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path));
ea25da48 Paolo Valente 2017-04-19  680  	bic->blkcg_serial_nr = serial_nr;
ea25da48 Paolo Valente 2017-04-19  681  out:
ea25da48 Paolo Valente 2017-04-19  682  	rcu_read_unlock();

:::::: The code at line 679 was first introduced by commit
:::::: 8f9bebc33dd718283183582fc4a762e178552fb8 block, bfq: access and cache blkg data only when safe

:::::: TO: Paolo Valente <paolo.valente@linaro.org>
:::::: CC: Jens Axboe <axboe@fb.com>

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