[kbuild-all] Re: [PATCH 2/2] bdi: Use might_alloc()

Hi Daniel, I love your patch! Yet something to improve: [auto build test ERROR on mmotm/master] url: https://github.com/0day-ci/linux/commits/Daniel-Vetter/mm-dmapool-Use-mig... base: git://git.cmpxchg.org/linux-mmotm.git master config: openrisc-randconfig-r011-20210113 (attached as .config) compiler: or1k-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/95ad71591084350229e768f9c2be5350d... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Daniel-Vetter/mm-dmapool-Use-might_alloc/20210113-215207 git checkout 95ad71591084350229e768f9c2be5350d504f896 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=openrisc If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): mm/backing-dev.c: In function 'wb_get_create': 647 | might_alloc(gfp); | ^~~~~~~~~~~ | might_lock cc1: some warnings being treated as errors vim +647 mm/backing-dev.c 616 617 /** 618 * wb_get_create - get wb for a given memcg, create if necessary 619 * @bdi: target bdi 620 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) 621 * @gfp: allocation mask to use 622 * 623 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to 624 * create one. The returned wb has its refcount incremented. 625 * 626 * This function uses css_get() on @memcg_css and thus expects its refcnt 627 * to be positive on invocation. IOW, rcu_read_lock() protection on 628 * @memcg_css isn't enough. try_get it before calling this function. 629 * 630 * A wb is keyed by its associated memcg. As blkcg implicitly enables 631 * memcg on the default hierarchy, memcg association is guaranteed to be 632 * more specific (equal or descendant to the associated blkcg) and thus can 633 * identify both the memcg and blkcg associations. 634 * 635 * Because the blkcg associated with a memcg may change as blkcg is enabled 636 * and disabled closer to root in the hierarchy, each wb keeps track of 637 * both the memcg and blkcg associated with it and verifies the blkcg on 638 * each lookup. On mismatch, the existing wb is discarded and a new one is 639 * created. 640 */ 641 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi, 642 struct cgroup_subsys_state *memcg_css, 643 gfp_t gfp) 644 { 645 struct bdi_writeback *wb; 646 648 649 if (!memcg_css->parent) 650 return &bdi->wb; 651 652 do { 653 rcu_read_lock(); 654 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); 655 if (wb) { 656 struct cgroup_subsys_state *blkcg_css; 657 658 /* see whether the blkcg association has changed */ 659 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, 660 &io_cgrp_subsys); 661 if (unlikely(wb->blkcg_css != blkcg_css || 662 !wb_tryget(wb))) 663 wb = NULL; 664 css_put(blkcg_css); 665 } 666 rcu_read_unlock(); 667 } while (!wb && !cgwb_create(bdi, memcg_css, gfp)); 668 669 return wb; 670 } 671 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org