On Mon, Apr 6, 2020 at 9:05 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Mon, Apr 06, 2020 at 08:54:07AM -0400, Yafang Shao wrote: > > When I run my memcg testcase which creates lots of memcgs, I found > > there're unexpected out of memory logs while there're still enough > > available free memory. The error log is, > > mkdir: cannot create directory 'foo.65533': Cannot allocate memory > > > > The reason is when we try to create more than MEM_CGROUP_ID_MAX memcgs, an > > -ENOMEM errno will be set by mem_cgroup_css_alloc(), but the right errno > > should be -ENOSPC, as explained above the function idr_alloc(). > > I think idr_alloc() is wrong. I think the right errno to return here is > EBUSY "Device or resource busy". > Agree with you that EBUSY is better. I will correct it. > > -static struct mem_cgroup *mem_cgroup_alloc(void) > > +static struct mem_cgroup *mem_cgroup_alloc(long *error) > > The normal way to do this is to return an ERR_PTR(). See > include/linux/err.h. > Thanks for your advise. I will take a look at it. Thanks Yafang
