On 6/14/20 8:38 AM, Muchun Song wrote:
> When a kmem_cache is initialized with SLAB_ACCOUNT slab flag, we must
> not call kmem_cache_alloc with __GFP_ACCOUNT GFP flag. In this case,
> we can be accounted to kmemcg twice. This is not correct. So we add a
Are you sure? How does that happen?
The only place I see these evaluated is this condition in slab_pre_alloc_hook():
if (memcg_kmem_enabled() &&
((flags & __GFP_ACCOUNT) || (s->flags & SLAB_ACCOUNT)))
return memcg_kmem_get_cache(s);
And it doesn't matter if one or both are set? Am I missing something?
> __GFP_ACCOUNT GFP flag check for slab allocation.
>
> We also introduce a new helper named fixup_gfp_flags to do that check.
> We can reuse the fixup_gfp_flags for SLAB/SLUB.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
> mm/slab.c | 10 +---------
> mm/slab.h | 21 +++++++++++++++++++++
> mm/slub.c | 10 +---------
> 3 files changed, 23 insertions(+), 18 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 9350062ffc1a..6e0110bef2d6 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -126,8 +126,6 @@
>
> #include <trace/events/kmem.h>
>
> -#include "internal.h"
> -
> #include "slab.h"
>
> /*
> @@ -2579,13 +2577,7 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep,
> * Be lazy and only check for valid flags here, keeping it out of the
> * critical path in kmem_cache_alloc().
> */
> - if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
> - gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
> - flags &= ~GFP_SLAB_BUG_MASK;
> - pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
> - invalid_mask, &invalid_mask, flags, &flags);
> - dump_stack();
> - }
> + flags = fixup_gfp_flags(cachep, flags);
> WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));
> local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);
>
> diff --git a/mm/slab.h b/mm/slab.h
> index 815e4e9a94cd..0b91f2a7b033 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -109,6 +109,7 @@ struct memcg_cache_params {
> #include <linux/kmemleak.h>
> #include <linux/random.h>
> #include <linux/sched/mm.h>
> +#include "internal.h"
>
> /*
> * State of the slab allocator.
> @@ -627,6 +628,26 @@ struct kmem_cache_node {
>
> };
>
> +static inline gfp_t fixup_gfp_flags(struct kmem_cache *s, gfp_t flags)
> +{
> + gfp_t invalid_mask = 0;
> +
> + if (unlikely(flags & GFP_SLAB_BUG_MASK))
> + invalid_mask |= flags & GFP_SLAB_BUG_MASK;
> +
> + if (unlikely(flags & __GFP_ACCOUNT && s->flags & SLAB_ACCOUNT))
> + invalid_mask |= __GFP_ACCOUNT;
> +
> + if (unlikely(invalid_mask)) {
> + flags &= ~invalid_mask;
> + pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
> + invalid_mask, &invalid_mask, flags, &flags);
> + dump_stack();
> + }
> +
> + return flags;
> +}
> +
> static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
> {
> return s->node[node];
> diff --git a/mm/slub.c b/mm/slub.c
> index b8f798b50d44..49b5cb7da318 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -37,8 +37,6 @@
>
> #include <trace/events/kmem.h>
>
> -#include "internal.h"
> -
> /*
> * Lock order:
> * 1. slab_mutex (Global Mutex)
> @@ -1745,13 +1743,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
>
> static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
> {
> - if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
> - gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
> - flags &= ~GFP_SLAB_BUG_MASK;
> - pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
> - invalid_mask, &invalid_mask, flags, &flags);
> - dump_stack();
> - }
> + flags = fixup_gfp_flags(s, flags);
>
> return allocate_slab(s,
> flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
>
