Messages in this thread | | | From | SeongJae Park <> | Subject | Re: [PATCH v1] mm/damon: add DAMON_OBJ macro | Date | Wed, 21 Sep 2022 16:41:43 +0000 |
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Hi Xin,
On Wed, 21 Sep 2022 11:49:42 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:
> In damon/sysfs.c file, we use 'container_of' macro to get > damon_sysfs_xxx struct instances, but i think it has a little > inconvenience, because we have to pass three arguments to > 'container_of', and the codes also look a bit long, so there i add a > 'DAMON_OBJ' macro, you just need to pass one arguments, then you can get > the right damon_sysfs_xxx struct instance.
Thank you always for your helps and efforts, but I have some comments below.
> > Signed-off-by: Xin Hao <xhao@linux.alibaba.com> > --- > include/linux/damon.h | 7 ++ > mm/damon/sysfs.c | 230 +++++++++++++++++------------------------- > 2 files changed, 102 insertions(+), 135 deletions(-) > > diff --git a/include/linux/damon.h b/include/linux/damon.h > index e7808a84675f..a3b577677caa 100644 > --- a/include/linux/damon.h > +++ b/include/linux/damon.h > @@ -24,6 +24,13 @@ static inline unsigned long damon_rand(unsigned long l, unsigned long r) > return l + prandom_u32_max(r - l); > } > > +/* > + * Get damon_sysfs_xxx relative struct instance. > + */ > +#define DAMON_OBJ(_type) ({ \ > + const typeof(((struct _type *)0)->kobj)*__mptr = (kobj); \ > + (struct _type *)((char *)__mptr - offsetof(struct _type, kobj)); }) > +
So, this macro assumes two implicit rules. 1. The caller would have a relevant 'struct kobject *' variable called 'kobj', and 2. The '_type' would have the field 'kobj'.
I think the implicit rules could make some people confused, so would be better to be well documented. Even though those are well documented, I think it cannot intuitively read by everyone. Making the name better self-explaining might help, but then the length of the code would be not so different.
So IMHO, this change makes the code a little bit shorter but unclear to understand what it does. And at least to my humble eyes, use of 'container_of()' makes the code a little bit more verbose, but clear to understand. I have no idea how we can make this code shorter while keeping it still easily understandable, and I think the level of verboseness is acceptable for the readability. So Nack at the moment, sorry.
Thanks, SJ
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