Re: [RFC][PATCH] hugetlb: add information and interface in sysfs [Was Re: [RFC][PATCH 4/5] Documentation: add node files to sysfs ABI]

[Greg KH <gregkh@suse.de>]

On Tue, Apr 29, 2008 at 11:14:15AM -0700, Nishanth Aravamudan wrote:
> On 29.04.2008 [10:22:43 -0700], Greg KH wrote:
> > On Tue, Apr 29, 2008 at 10:11:15AM -0700, Nishanth Aravamudan wrote:
> > > +struct hstate_attribute {
> > > +	struct attribute attr;
> > > +	ssize_t (*show)(struct hstate *h, char *buf);
> > > +	ssize_t (*store)(struct hstate *h, const char *buf, size_t count);
> > > +};
> > 
> > Do you need your own attribute type with show and store?  Can't you just
> > use the "default" kobject attributes?
> 
> Hrm, I don't know? Probably. Like I said, I was using the
> /sys/kernel/slab code as my reference. Can you explain this more? Or
> just point me to the source/documentation I should read for info.

Documentation/kobject.txt, with sample examples in samples/kobject/ for
you to copy and use.

> Are you referring to kobj_attr_show/kobj_attr_store? Should I just be
> using kobj_sysfs_ops, then, most likely?

See the above examples for more details.

> > Also, you have no release function for your kobject to be cleaned up,
> > that's a major bug.
> 
> Well, these kobjects never go away? They will be statically initialized
> at boot-time and then stick around until the kernel goes away. Looking
> at /sys/kernel/slab's code, again, the release() function there does a
> kfree() on the containing kmem_cache, but for hugetlb, the hstates are
> static... If we do move to dynamic allocations ever (or allow adding
> hugepage sizes at run-time somehow), then perhaps we'll need a release
> method then?

Yes you will.  Please always create one, what happens when you want to
clean them up at shut-down time...

thanks,

greg k-h

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