Re: [PATCH v4] mm: cma: support sysfs

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Mar 19, 2021 at 05:19:47PM +0300, Dmitry Osipenko wrote:
> 19.03.2021 16:51, Dmitry Osipenko пишет:
> > 19.03.2021 16:47, Greg Kroah-Hartman пишет:
> >> On Fri, Mar 19, 2021 at 04:45:21PM +0300, Dmitry Osipenko wrote:
> >>> 19.03.2021 16:42, Greg Kroah-Hartman пишет:
> >>>> On Fri, Mar 19, 2021 at 04:39:41PM +0300, Dmitry Osipenko wrote:
> >>>>> 19.03.2021 15:44, Dmitry Osipenko пишет:
> >>>>> ...
> >>>>>>>  #include <linux/debugfs.h>
> >>>>>>> +#include <linux/kobject.h>
> >>>>>>> +
> >>>>>>> +struct cma_stat {
> >>>>>>> +	spinlock_t lock;
> >>>>>>> +	/* the number of CMA page successful allocations */
> >>>>>>> +	unsigned long nr_pages_succeeded;
> >>>>>>> +	/* the number of CMA page allocation failures */
> >>>>>>> +	unsigned long nr_pages_failed;
> >>>>>>> +	struct kobject kobj;
> >>>>>>> +};
> >>>>>>>  
> >>>>>>>  struct cma {
> >>>>>>>  	unsigned long   base_pfn;
> >>>>>>> @@ -16,6 +26,9 @@ struct cma {
> >>>>>>>  	struct debugfs_u32_array dfs_bitmap;
> >>>>>>>  #endif
> >>>>>>>  	char name[CMA_MAX_NAME];
> >>>>>>> +#ifdef CONFIG_CMA_SYSFS
> >>>>>>> +	struct cma_stat	*stat;
> >>>>>>> +#endif
> >>>>>
> >>>>> What is the point of allocating stat dynamically?
> >>>>
> >>>> Because static kobjects make me cry.
> >>>>
> >>>
> >>> I meant that it's already a part of struct cma, it looks like the stat
> >>> could be embedded into struct cma and then kobj could be initialized
> >>> separately.
> >>
> >> But that structure is statically allocated, so it can not be.  This has
> >> been discussed in the past threads for when this was reviewed if you are
> >> curious :)
> > 
> > Indeed, I missed that cma_areas[] is static, thank you.
> > 
> 
> And in this case should be better to make only the kobj allocated
> dynamically instead of the whole cma_stat.

Why does it matter?