Re: [PATCH v4 06/22] mm/zsmalloc: convert create_page_chain() and its users to use zpdesc

[Vishal Moola <vishal.moola@gmail.com>]

On Mon, Aug 05, 2024 at 04:20:15PM +0800, Alex Shi wrote:
> 
> 
> On 8/3/24 3:09 AM, Vishal Moola wrote:
> > On Mon, Jul 29, 2024 at 07:25:18PM +0800, alexs@kernel.org wrote:
> >> From: Alex Shi <alexs@kernel.org>
> >>
> >> Introduce a few helper functions for conversion to convert create_page_chain()
> >> to use zpdesc, then use zpdesc in replace_sub_page() too.
> > 
> > As a general note, I've been having trouble keeping track of your helper
> > functions throughout your patchset. Things get confusing when helper
> > functions are "add-ons" to patches and are then replaced/rewritten
> > in various subsequent patches - might just be me though.
> 
> Right, maybe too much helper doesn't give necessary help.
> 
> > 
> >> Originally-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> >> Signed-off-by: Alex Shi <alexs@kernel.org>
> >> ---
> >>  mm/zpdesc.h   |   6 +++
> >>  mm/zsmalloc.c | 115 +++++++++++++++++++++++++++++++++-----------------
> >>  2 files changed, 82 insertions(+), 39 deletions(-)
> >>
> >> diff --git a/mm/zpdesc.h b/mm/zpdesc.h
> >> index 79ec40b03956..2293453f5d57 100644
> >> --- a/mm/zpdesc.h
> >> +++ b/mm/zpdesc.h
> >> @@ -102,4 +102,10 @@ static inline struct zpdesc *pfn_zpdesc(unsigned long pfn)
> >>  {
> >>  	return page_zpdesc(pfn_to_page(pfn));
> >>  }
> >> +
> >> +static inline void __zpdesc_set_movable(struct zpdesc *zpdesc,
> >> +					const struct movable_operations *mops)
> >> +{
> >> +	__SetPageMovable(zpdesc_page(zpdesc), mops);
> >> +}
> >>  #endif
> >> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> >> index bbc165cb587d..a8f390beeab8 100644
> >> --- a/mm/zsmalloc.c
> >> +++ b/mm/zsmalloc.c
> >> @@ -248,6 +248,41 @@ static inline void *zpdesc_kmap_atomic(struct zpdesc *zpdesc)
> >>  	return kmap_atomic(zpdesc_page(zpdesc));
> >>  }
> >>  
> >> +static inline void zpdesc_set_zspage(struct zpdesc *zpdesc,
> >> +				     struct zspage *zspage)
> >> +{
> >> +	zpdesc->zspage = zspage;
> >> +}
> >> +
> >> +static inline void zpdesc_set_first(struct zpdesc *zpdesc)
> >> +{
> >> +	SetPagePrivate(zpdesc_page(zpdesc));
> >> +}
> >> +
> > 
> > I'm not a fan of the names above. IMO, naming should follow some
> > semblance of consistency regarding their purpose (or have comments
> > that describe their purpose instead).
> > 
> > At a glance zpdesc_set_zspage() and zpdesc_set_first() sound like they
> > are doing similar things, but I don't think they serve similar purposes?
> 
> zpdesc_set_zspage() only used in one place, a helper maynot needed. Let me remove it.
> Same thing for the alloc_zpdesc() and free_zpdesc(), they could be merge into using place.

alloc_zpdesc() and free_zpdesc() are fine as is. The helper functions
will be useful whenever memdescs can be allocated on their own, so its
better to introduce it now.

> Thanks
> Alex
> > 
> >> +static inline void zpdesc_inc_zone_page_state(struct zpdesc *zpdesc)
> >> +{
> >> +	inc_zone_page_state(zpdesc_page(zpdesc), NR_ZSPAGES);
> >> +}
> >> +
> >> +static inline void zpdesc_dec_zone_page_state(struct zpdesc *zpdesc)
> >> +{
> >> +	dec_zone_page_state(zpdesc_page(zpdesc), NR_ZSPAGES);
> >> +}
> >> +
> >> +static inline struct zpdesc *alloc_zpdesc(gfp_t gfp)
> >> +{
> >> +	struct page *page = alloc_page(gfp);
> >> +
> >> +	return page_zpdesc(page);
> >> +}
> >> +
> >> +static inline void free_zpdesc(struct zpdesc *zpdesc)
> >> +{
> >> +	struct page *page = zpdesc_page(zpdesc);
> >> +
> >> +	__free_page(page);
> >> +}
> >> +
> >