This patch isolates the check for whether memcg accounts hugetlb.
This condition can only be true if the memcg mount option
memory_hugetlb_accounting is on, which includes hugetlb usage
in memory.current.

Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>

---
 mm/memcontrol.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f3a9653cef0e..97f63ec9c9fb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1425,6 +1425,9 @@ unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item)
 		memcg_page_state_output_unit(item);
 }
 
+/* Forward declaration */
+bool memcg_accounts_hugetlb(void);
+
 static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
 {
 	int i;
@@ -1446,7 +1449,7 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
 
 #ifdef CONFIG_HUGETLB_PAGE
 		if (unlikely(memory_stats[i].idx == NR_HUGETLB) &&
-		    !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
+			!memcg_accounts_hugetlb())
 			continue;
 #endif
 		size = memcg_page_state_output(memcg, memory_stats[i].idx);
@@ -4483,6 +4486,15 @@ int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
 	return ret;
 }
 
+bool memcg_accounts_hugetlb(void)
+{
+#ifdef CONFIG_HUGETLB_PAGE
+	return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
+#else
+	return false;
+#endif
+}
+
 /**
  * mem_cgroup_hugetlb_try_charge - try to charge the memcg for a hugetlb folio
  * @memcg: memcg to charge.
@@ -4508,8 +4520,7 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
 	 * but do not attempt to commit charge later (or cancel on error) either.
 	 */
 	if (mem_cgroup_disabled() || !memcg ||
-		!cgroup_subsys_on_dfl(memory_cgrp_subsys) ||
-		!(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
+		!cgroup_subsys_on_dfl(memory_cgrp_subsys) || !memcg_accounts_hugetlb())
 		return -EOPNOTSUPP;
 
 	if (try_charge(memcg, gfp, nr_pages))
-- 
2.43.5

On Fri, Nov 08, 2024 at 01:29:44PM -0800, Joshua Hahn wrote:
> This patch isolates the check for whether memcg accounts hugetlb.
> This condition can only be true if the memcg mount option
> memory_hugetlb_accounting is on, which includes hugetlb usage
> in memory.current.
> 
> Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> 
> ---
>  mm/memcontrol.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f3a9653cef0e..97f63ec9c9fb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1425,6 +1425,9 @@ unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item)
>  		memcg_page_state_output_unit(item);
>  }
>  
> +/* Forward declaration */
> +bool memcg_accounts_hugetlb(void);

No need for forward declaration. Just define it here and make it static.

> +
>  static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>  {
>  	int i;
> @@ -1446,7 +1449,7 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>  
>  #ifdef CONFIG_HUGETLB_PAGE
>  		if (unlikely(memory_stats[i].idx == NR_HUGETLB) &&
> -		    !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
> +			!memcg_accounts_hugetlb())
>  			continue;
>  #endif
>  		size = memcg_page_state_output(memcg, memory_stats[i].idx);
> @@ -4483,6 +4486,15 @@ int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
>  	return ret;
>  }
>  
> +bool memcg_accounts_hugetlb(void)
> +{
> +#ifdef CONFIG_HUGETLB_PAGE
> +	return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
> +#else
> +	return false;
> +#endif
> +}
> +
>  /**
>   * mem_cgroup_hugetlb_try_charge - try to charge the memcg for a hugetlb folio
>   * @memcg: memcg to charge.
> @@ -4508,8 +4520,7 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
>  	 * but do not attempt to commit charge later (or cancel on error) either.
>  	 */
>  	if (mem_cgroup_disabled() || !memcg ||
> -		!cgroup_subsys_on_dfl(memory_cgrp_subsys) ||
> -		!(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
> +		!cgroup_subsys_on_dfl(memory_cgrp_subsys) || !memcg_accounts_hugetlb())
>  		return -EOPNOTSUPP;
>  
>  	if (try_charge(memcg, gfp, nr_pages))
> -- 
> 2.43.5
>

On Fri, Nov 8, 2024 at 2:21 PM Shakeel Butt <shakeel.butt@linux.dev> wrote:
>
> On Fri, Nov 08, 2024 at 01:29:44PM -0800, Joshua Hahn wrote:
> > This patch isolates the check for whether memcg accounts hugetlb.
> > This condition can only be true if the memcg mount option
> > memory_hugetlb_accounting is on, which includes hugetlb usage
> > in memory.current.
> >
> > Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> >
> > ---
> >  mm/memcontrol.c | 17 ++++++++++++++---
> >  1 file changed, 14 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index f3a9653cef0e..97f63ec9c9fb 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -1425,6 +1425,9 @@ unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item)
> >               memcg_page_state_output_unit(item);
> >  }
> >
> > +/* Forward declaration */
> > +bool memcg_accounts_hugetlb(void);
>
> No need for forward declaration. Just define it here and make it static.

Also please pull the #ifdef outside the function definition, e.g.

#ifdef CONFIG_HUGETLB_PAGE
static bool memcg_accounts_hugetlb(void)
{
     return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
}
#else /* CONFIG_HUGETLB_PAGE */
static bool memcg_accounts_hugetlb(void) { return false; }
{
     return false;
}
#endif /* CONFIG_HUGETLB_PAGE */

>
> > +
> >  static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> >  {
> >       int i;
> > @@ -1446,7 +1449,7 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> >
> >  #ifdef CONFIG_HUGETLB_PAGE
> >               if (unlikely(memory_stats[i].idx == NR_HUGETLB) &&
> > -                 !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
> > +                     !memcg_accounts_hugetlb())
> >                       continue;
> >  #endif
> >               size = memcg_page_state_output(memcg, memory_stats[i].idx);
> > @@ -4483,6 +4486,15 @@ int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
> >       return ret;
> >  }
> >
> > +bool memcg_accounts_hugetlb(void)
> > +{
> > +#ifdef CONFIG_HUGETLB_PAGE
> > +     return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
> > +#else
> > +     return false;
> > +#endif
> > +}
> > +
> >  /**
> >   * mem_cgroup_hugetlb_try_charge - try to charge the memcg for a hugetlb folio
> >   * @memcg: memcg to charge.
> > @@ -4508,8 +4520,7 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
> >        * but do not attempt to commit charge later (or cancel on error) either.
> >        */
> >       if (mem_cgroup_disabled() || !memcg ||
> > -             !cgroup_subsys_on_dfl(memory_cgrp_subsys) ||
> > -             !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
> > +             !cgroup_subsys_on_dfl(memory_cgrp_subsys) || !memcg_accounts_hugetlb())
> >               return -EOPNOTSUPP;
> >
> >       if (try_charge(memcg, gfp, nr_pages))
> > --
> > 2.43.5
> >
>

On Fri, Nov 8, 2024 at 6:03 PM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Fri, Nov 8, 2024 at 2:21 PM Shakeel Butt <shakeel.butt@linux.dev> wrote:
> >
> > On Fri, Nov 08, 2024 at 01:29:44PM -0800, Joshua Hahn wrote:
> > > This patch isolates the check for whether memcg accounts hugetlb.
> > > This condition can only be true if the memcg mount option
> > > memory_hugetlb_accounting is on, which includes hugetlb usage
> > > in memory.current.
> > >
> > > Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> > >
> > > ---
> > >  mm/memcontrol.c | 17 ++++++++++++++---
> > >  1 file changed, 14 insertions(+), 3 deletions(-)
> > > +/* Forward declaration */
> > > +bool memcg_accounts_hugetlb(void);
> >
> > No need for forward declaration. Just define it here and make it static.
>
> Also please pull the #ifdef outside the function definition, e.g.
>
> #ifdef CONFIG_HUGETLB_PAGE
> static bool memcg_accounts_hugetlb(void)
> {
>      return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
> }
> #else /* CONFIG_HUGETLB_PAGE */
> static bool memcg_accounts_hugetlb(void) { return false; }
> {
>      return false;
> }
> #endif /* CONFIG_HUGETLB_PAGE */
>

Hello Shakeel and Yosry,

Thank you for taking the time to review my patch.
Yes -- I will just declare the function & make it static. It was my
intention to group the new memcg charging functions together,
and in that effort I just made a forward declaration above.
However, I think that it does make the code look a bit more
messy, which is against the spirit of this patch series!

And Yosry, thank you for your feedback, I will separate the
definitions based on the #ifdef.

Thank you both, I hope you have a great day!
Joshua