On Wed, Feb 03, 2021 at 07:50:01AM -0800, Minchan Kim wrote: > +++ b/mm/Makefile > @@ -106,6 +106,7 @@ obj-$(CONFIG_ZSMALLOC) += zsmalloc.o > obj-$(CONFIG_Z3FOLD) += z3fold.o > obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o > obj-$(CONFIG_CMA) += cma.o > +obj-$(CONFIG_SYSFS) += cma_sysfs.o ehh ... if we have a kernel build with CMA=n, SYSFS=y, we'll get cma_sysfs built in with no cma to report on. > +static ssize_t cma_alloc_attempt_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + unsigned long val; > + struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj); > + > + val = stat->alloc_attempt; > + > + return sysfs_emit(buf, "%lu\n", val); Why not more simply: { struct cma_stat *stat = container_of(kobj, struct cma_stat, kobj); return sysfs_emit(buf, "%lu\n", stat->alloc_attempt); } > + for (i = 0; i < cma_area_count; i++) { > + cma = &cma_areas[i]; > + stat = kzalloc(sizeof(*stat), GFP_KERNEL); > + if (!stat) > + goto out; How many cma areas are there going to be? do we really want to allocate their stat individually?