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SubjectRe: [PATCH] mm: cma: support sysfs
On Fri, Feb 05, 2021 at 02:55:26AM +0000, Matthew Wilcox wrote:
> 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.

OMG. Let me fix it.

>
> > +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);

It's a legacy when I used the lock there but removed finally.
Will follow your suggestion.

> }
>
> > + 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?

I am not sure what could be in the end but at least, I have
5+ candidates (but could be shrink or extend) and yes,
want to keep track them individually.
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