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McKenney" , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Zqiang , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , rcu@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 6/8] mm/slab: wrap rcu sheaf handling with ifdef Date: Thu, 16 Apr 2026 18:10:20 +0900 Message-ID: <20260416091022.36823-7-harry@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260416091022.36823-1-harry@kernel.org> References: <20260416091022.36823-1-harry@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 8F54040005 X-Stat-Signature: 9ar14ijtu94u7hq1tj9q6fzuoszx4896 X-Rspam-User: X-HE-Tag: 1776330648-798629 X-HE-Meta: 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 aqEfHape 3pGW5AQMQ3d2FW7x9QtFDzVyP7EL9OQ/HnVAq+2/ZYFs3IL0G9PNOaB84zDJBHHRCENP2/g65XlN6f+Tzi0GwCuQi9KGQCy+DjjlHDNFaZ5GH/C3NBs0zh1AgCxaSwkhc9tHUsTATHR/cbOp19t8W9eHJJTD+xTuxMe0HseU4s4wozC/tPgKd244b4NxuewCuXg59jCswnVRaCRmZnp/mx8O74SEt55xOikxzLuD4aUpJRa4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Freeing objects via rcu sheaves is only done with CONFIG_KVFREE_RCU_BATCHED. Wrap the related functions and struct fields with ifdef to make this dependency explicit. Also remove a TODO about implementing __kvfree_rcu_barrier_on_cache() for a specific slab cache, as there doesn't seem to be a simple and effective way to do so. Signed-off-by: Harry Yoo (Oracle) --- mm/slab.h | 3 +++ mm/slab_common.c | 4 ---- mm/slub.c | 27 +++++++++++++++++++++++++-- 3 files changed, 28 insertions(+), 6 deletions(-) diff --git a/mm/slab.h b/mm/slab.h index d7fd7626e9fe..bdad5f389490 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -409,9 +409,12 @@ static inline bool is_kmalloc_normal(struct kmem_cache *s) return !(s->flags & (SLAB_CACHE_DMA|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT)); } +#ifdef CONFIG_KVFREE_RCU_BATCHED bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj, bool allow_spin); void flush_all_rcu_sheaves(void); void flush_rcu_sheaves_on_cache(struct kmem_cache *s); +#endif + void defer_kvfree_rcu_barrier(void); #define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | \ diff --git a/mm/slab_common.c b/mm/slab_common.c index 46a2bee1662b..347e52f1538c 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -2289,10 +2289,6 @@ void kvfree_rcu_barrier_on_cache(struct kmem_cache *s) rcu_barrier(); } - /* - * TODO: Introduce a version of __kvfree_rcu_barrier() that works - * on a specific slab cache. - */ __kvfree_rcu_barrier(); } EXPORT_SYMBOL_GPL(kvfree_rcu_barrier_on_cache); diff --git a/mm/slub.c b/mm/slub.c index d0db8d070570..91b8827d65da 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -421,7 +421,9 @@ struct slub_percpu_sheaves { local_trylock_t lock; struct slab_sheaf *main; /* never NULL when unlocked */ struct slab_sheaf *spare; /* empty or full, may be NULL */ +#ifdef CONFIG_KVFREE_RCU_BATCHED struct slab_sheaf *rcu_free; /* for batching kfree_rcu() */ +#endif }; /* @@ -2923,6 +2925,7 @@ static void sheaf_flush_unused(struct kmem_cache *s, struct slab_sheaf *sheaf) sheaf->size = 0; } +#ifdef CONFIG_KVFREE_RCU_BATCHED static bool __rcu_free_sheaf_prepare(struct kmem_cache *s, struct slab_sheaf *sheaf) { @@ -2965,6 +2968,7 @@ static void rcu_free_sheaf_nobarn(struct rcu_head *head) free_empty_sheaf(s, sheaf); } +#endif /* * Caller needs to make sure migration is disabled in order to fully flush @@ -2978,7 +2982,10 @@ static void rcu_free_sheaf_nobarn(struct rcu_head *head) static void pcs_flush_all(struct kmem_cache *s) { struct slub_percpu_sheaves *pcs; - struct slab_sheaf *spare, *rcu_free; + struct slab_sheaf *spare; +#ifdef CONFIG_KVFREE_RCU_BATCHED + struct slab_sheaf *rcu_free; +#endif local_lock(&s->cpu_sheaves->lock); pcs = this_cpu_ptr(s->cpu_sheaves); @@ -2986,8 +2993,10 @@ static void pcs_flush_all(struct kmem_cache *s) spare = pcs->spare; pcs->spare = NULL; +#ifdef CONFIG_KVFREE_RCU_BATCHED rcu_free = pcs->rcu_free; pcs->rcu_free = NULL; +#endif local_unlock(&s->cpu_sheaves->lock); @@ -2996,8 +3005,10 @@ static void pcs_flush_all(struct kmem_cache *s) free_empty_sheaf(s, spare); } +#ifdef CONFIG_KVFREE_RCU_BATCHED if (rcu_free) call_rcu(&rcu_free->rcu_head, rcu_free_sheaf_nobarn); +#endif sheaf_flush_main(s); } @@ -3016,10 +3027,12 @@ static void __pcs_flush_all_cpu(struct kmem_cache *s, unsigned int cpu) pcs->spare = NULL; } +#ifdef CONFIG_KVFREE_RCU_BATCHED if (pcs->rcu_free) { call_rcu(&pcs->rcu_free->rcu_head, rcu_free_sheaf_nobarn); pcs->rcu_free = NULL; } +#endif } static void pcs_destroy(struct kmem_cache *s) @@ -3056,7 +3069,9 @@ static void pcs_destroy(struct kmem_cache *s) */ WARN_ON(pcs->spare); +#ifdef CONFIG_KVFREE_RCU_BATCHED WARN_ON(pcs->rcu_free); +#endif if (!WARN_ON(pcs->main->size)) { free_empty_sheaf(s, pcs->main); @@ -3937,7 +3952,11 @@ static bool has_pcs_used(int cpu, struct kmem_cache *s) pcs = per_cpu_ptr(s->cpu_sheaves, cpu); - return (pcs->spare || pcs->rcu_free || pcs->main->size); +#ifdef CONFIG_KVFREE_RCU_BATCHED + if (pcs->rcu_free) + return true; +#endif + return (pcs->spare || pcs->main->size); } /* @@ -3995,6 +4014,7 @@ static void flush_all(struct kmem_cache *s) cpus_read_unlock(); } +#ifdef CONFIG_KVFREE_RCU_BATCHED static void flush_rcu_sheaf(struct work_struct *w) { struct slub_percpu_sheaves *pcs; @@ -4071,6 +4091,7 @@ void flush_all_rcu_sheaves(void) rcu_barrier(); } +#endif /* CONFIG_KVFREE_RCU_BATCHED */ static int slub_cpu_setup(unsigned int cpu) { @@ -5825,6 +5846,7 @@ bool free_to_pcs(struct kmem_cache *s, void *object, bool allow_spin) return true; } +#ifdef CONFIG_KVFREE_RCU_BATCHED static void rcu_free_sheaf(struct rcu_head *head) { struct slab_sheaf *sheaf; @@ -6005,6 +6027,7 @@ bool __kfree_rcu_sheaf(struct kmem_cache *s, void *obj, bool allow_spin) lock_map_release(&kfree_rcu_sheaf_map); return false; } +#endif /* CONFIG_KVFREE_RCU_BATCHED */ static __always_inline bool can_free_to_pcs(struct slab *slab) { -- 2.43.0