Re: [PATCH v2 07/16] mm/slab: replace struct partial_context with slab_alloc_context

[Hao Li <hao.li@linux.dev>]

On Wed, Jun 10, 2026 at 05:40:09PM +0200, Vlastimil Babka (SUSE) wrote:
> Refactor get_from_partial_node(), get_from_any_partial(),
> get_from_partial() and ___slab_alloc().
> 
> Remove struct partial_context, which used to be more substantial but
> shrank as part of the sheaves conversion. Instead pass gfp_flags and
> pointer to the new slab_alloc_context, which together is a superset of
> partial_context.
> 
> This means alloc_flags are now available and we can use them to
> determine if spinning is allowed, further reducing false positive "not
> allowed" in the slow path due to gfp flags lacking __GFP_RECLAIM.
> 
> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> ---
>  mm/slub.c | 52 ++++++++++++++++++++++++----------------------------
>  1 file changed, 24 insertions(+), 28 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index ef745b37d063..98b79e5e7679 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -220,12 +220,6 @@ struct slab_alloc_context {
>  	unsigned int alloc_flags;
>  };
>  
> -/* Structure holding parameters for get_from_partial() call chain */
> -struct partial_context {
> -	gfp_t flags;
> -	unsigned int orig_size;
> -};
> -
>  /* Structure holding parameters for get_partial_node_bulk() */
>  struct partial_bulk_context {
>  	gfp_t flags;
> @@ -3826,7 +3820,8 @@ static bool get_partial_node_bulk(struct kmem_cache *s,
>   */
>  static void *get_from_partial_node(struct kmem_cache *s,
>  				   struct kmem_cache_node *n,
> -				   struct partial_context *pc)
> +				   gfp_t gfp_flags,
> +				   struct slab_alloc_context *ac)
>  {
>  	struct slab *slab, *slab2;
>  	unsigned long flags;
> @@ -3841,7 +3836,7 @@ static void *get_from_partial_node(struct kmem_cache *s,
>  	if (!n || !n->nr_partial)
>  		return NULL;
>  
> -	if (gfpflags_allow_spinning(pc->flags))
> +	if (alloc_flags_allow_spinning(ac->alloc_flags))
>  		spin_lock_irqsave(&n->list_lock, flags);
>  	else if (!spin_trylock_irqsave(&n->list_lock, flags))
>  		return NULL;
> @@ -3849,12 +3844,12 @@ static void *get_from_partial_node(struct kmem_cache *s,
>  
>  		struct freelist_counters old, new;
>  
> -		if (!pfmemalloc_match(slab, pc->flags))
> +		if (!pfmemalloc_match(slab, gfp_flags))
>  			continue;
>  
>  		if (IS_ENABLED(CONFIG_SLUB_TINY) || kmem_cache_debug(s)) {
>  			object = alloc_single_from_partial(s, n, slab,
> -							pc->orig_size);
> +							ac->orig_size);
>  			if (object)
>  				break;
>  			continue;
> @@ -3888,15 +3883,16 @@ static void *get_from_partial_node(struct kmem_cache *s,
>  /*
>   * Get an object from somewhere. Search in increasing NUMA distances.
>   */
> -static void *get_from_any_partial(struct kmem_cache *s, struct partial_context *pc)
> +static void *get_from_any_partial(struct kmem_cache *s, gfp_t gfp_flags,
> +				  struct slab_alloc_context *ac)
>  {
>  #ifdef CONFIG_NUMA
>  	struct zonelist *zonelist;
>  	struct zoneref *z;
>  	struct zone *zone;
> -	enum zone_type highest_zoneidx = gfp_zone(pc->flags);
> +	enum zone_type highest_zoneidx = gfp_zone(gfp_flags);
>  	unsigned int cpuset_mems_cookie;
> -	bool allow_spin = gfpflags_allow_spinning(pc->flags);
> +	bool allow_spin = alloc_flags_allow_spinning(ac->alloc_flags);
>  
>  	/*
>  	 * The defrag ratio allows a configuration of the tradeoffs between
> @@ -3930,16 +3926,17 @@ static void *get_from_any_partial(struct kmem_cache *s, struct partial_context *
>  		if (allow_spin)
>  			cpuset_mems_cookie = read_mems_allowed_begin();
>  
> -		zonelist = node_zonelist(mempolicy_slab_node(), pc->flags);
> +		zonelist = node_zonelist(mempolicy_slab_node(), gfp_flags);
>  		for_each_zone_zonelist(zone, z, zonelist, highest_zoneidx) {
>  			struct kmem_cache_node *n;
>  
>  			n = get_node(s, zone_to_nid(zone));
>  
> -			if (n && cpuset_zone_allowed(zone, pc->flags) &&
> +			if (n && cpuset_zone_allowed(zone, gfp_flags) &&
>  					n->nr_partial > s->min_partial) {
>  
> -				void *object = get_from_partial_node(s, n, pc);
> +				void *object = get_from_partial_node(s, n,
> +								gfp_flags, ac);
>  
>  				if (object) {
>  					/*
> @@ -3961,8 +3958,8 @@ static void *get_from_any_partial(struct kmem_cache *s, struct partial_context *
>  /*
>   * Get an object from a partial slab
>   */
> -static void *get_from_partial(struct kmem_cache *s, int node,
> -			      struct partial_context *pc)
> +static void *get_from_partial(struct kmem_cache *s, int node, gfp_t flags,
> +			      struct slab_alloc_context *ac)
>  {
>  	int searchnode = node;
>  	void *object;
> @@ -3970,11 +3967,11 @@ static void *get_from_partial(struct kmem_cache *s, int node,
>  	if (node == NUMA_NO_NODE)
>  		searchnode = numa_mem_id();
>  
> -	object = get_from_partial_node(s, get_node(s, searchnode), pc);
> -	if (object || (node != NUMA_NO_NODE && (pc->flags & __GFP_THISNODE)))
> +	object = get_from_partial_node(s, get_node(s, searchnode), flags, ac);
> +	if (object || (node != NUMA_NO_NODE && (flags & __GFP_THISNODE)))
>  		return object;
>  
> -	return get_from_any_partial(s, pc);
> +	return get_from_any_partial(s, flags, ac);
>  }
>  
>  static bool has_pcs_used(int cpu, struct kmem_cache *s)
> @@ -4454,16 +4451,16 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>  			   struct slab_alloc_context *ac)
>  {
>  	bool allow_spin = alloc_flags_allow_spinning(ac->alloc_flags);
> +	gfp_t trynode_flags;
>  	void *object;
>  	struct slab *slab;
> -	struct partial_context pc;
>  	bool try_thisnode = true;
>  
>  	stat(s, ALLOC_SLOWPATH);
>  
>  new_objects:
>  
> -	pc.flags = gfpflags;
> +	trynode_flags = gfpflags;
>  	/*
>  	 * When a preferred node is indicated but no __GFP_THISNODE
>  	 *
> @@ -4479,17 +4476,16 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>  		     && try_thisnode)) {
>  		if (unlikely(!allow_spin))
>  			/* Do not upgrade gfp to NOWAIT from more restrictive mode */
> -			pc.flags = gfpflags | __GFP_THISNODE;
> +			trynode_flags = gfpflags | __GFP_THISNODE;
>  		else
> -			pc.flags = GFP_NOWAIT | __GFP_THISNODE;
> +			trynode_flags = GFP_NOWAIT | __GFP_THISNODE;

nit: the comment "__GFP_THISNODE in pc.flags" also needs to be updated to "trynode_flags"

otherwise, looks good to me.
Reviewed-by: Hao Li <hao.li@linux.dev>

-- 
Thanks,
Hao