Re: [PATCH 04/11] mm/zsmalloc: Introduce objcgs pointer in struct zspage

Joshua Hahn
2026-03-11T20:22:42Z

On Wed, 11 Mar 2026 13:17:22 -0700 Nhat Pham <nphamcs@gmail.com> wrote:

> On Wed, Mar 11, 2026 at 12:52 PM Joshua Hahn <joshua.hahnjy@gmail.com> wrote:
> >
> > Introduce an array of struct obj_cgroup pointers to zspage to keep track
> > of compressed objects' memcg ownership, if the zs_pool has been made to
> > be memcg-aware at creation time.
> >
> > Move the error path for alloc_zspage to a jump label to simplify the
> > growing error handling path for a failed zpdesc allocation.
> >
> > Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
> > Suggested-by: Harry Yoo <harry.yoo@oracle.com>
> > Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> > ---
> > mm/zsmalloc.c | 34 ++++++++++++++++++++++++++--------
> > 1 file changed, 26 insertions(+), 8 deletions(-)
> >
> > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > index 3f0f42b78314..dcf99516227c 100644
> > --- a/mm/zsmalloc.c
> > +++ b/mm/zsmalloc.c
> > @@ -39,6 +39,7 @@
> > #include <linux/zsmalloc.h>
> > #include <linux/fs.h>
> > #include <linux/workqueue.h>
> > +#include <linux/memcontrol.h>
> > #include "zpdesc.h"
> >
> > #define ZSPAGE_MAGIC 0x58
> > @@ -273,6 +274,7 @@ struct zspage {
> > struct zpdesc *first_zpdesc;
> > struct list_head list; /* fullness list */
> > struct zs_pool *pool;
> > + struct obj_cgroup **objcgs;
> > struct zspage_lock zsl;
> > };
> >
> > @@ -825,6 +827,8 @@ static void __free_zspage(struct zs_pool *pool, struct size_class *class,
> > zpdesc = next;
> > } while (zpdesc != NULL);
> >
> > + if (pool->memcg_aware)
> > + kfree(zspage->objcgs);
> > cache_free_zspage(zspage);
> >
> > class_stat_sub(class, ZS_OBJS_ALLOCATED, class->objs_per_zspage);
> > @@ -946,6 +950,16 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
> > if (!IS_ENABLED(CONFIG_COMPACTION))
> > gfp &= ~__GFP_MOVABLE;
> >
> > + if (pool->memcg_aware) {
> > + zspage->objcgs = kcalloc(class->objs_per_zspage,
> > + sizeof(struct obj_cgroup *),
> > + gfp & ~__GFP_HIGHMEM);
>
> I remembered asking this, so my apologies if I missed/forgot your
> response - but would vmalloc work here? i.e kvcalloc to fallback to
> vmalloc etc.?

Hello Nhat : -)

Thank you for reviewing, and for your acks on the other parts!

You're right, I missed changing that on my end after v1. No reason
vmalloc shouldn't work here, let me make that change in v3.

Thanks, I hope you have a great day!
Joshua