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bpf: Remove bpf_selem_free_fields*_rcu
This patch removes the bpf_selem_free_fields*_rcu. The bpf_obj_free_fields() can be done before the call_rcu_trasks_trace() and kfree_rcu(). It is needed when a later patch uses bpf_mem_cache_alloc/free. In bpf hashtab, bpf_obj_free_fields() is also called before calling bpf_mem_cache_free. The discussion can be found in https://lore.kernel.org/bpf/f67021ee-21d9-bfae-6134-4ca542fab843@linux.dev/ Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Link: https://lore.kernel.org/r/20230308065936.1550103-8-martin.lau@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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@ -109,27 +109,6 @@ static void bpf_local_storage_free_rcu(struct rcu_head *rcu)
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kfree_rcu(local_storage, rcu);
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}
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static void bpf_selem_free_fields_rcu(struct rcu_head *rcu)
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{
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struct bpf_local_storage_elem *selem;
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struct bpf_local_storage_map *smap;
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selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
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/* protected by the rcu_barrier*() */
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smap = rcu_dereference_protected(SDATA(selem)->smap, true);
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bpf_obj_free_fields(smap->map.record, SDATA(selem)->data);
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kfree(selem);
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}
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static void bpf_selem_free_fields_trace_rcu(struct rcu_head *rcu)
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{
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/* Free directly if Tasks Trace RCU GP also implies RCU GP */
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if (rcu_trace_implies_rcu_gp())
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bpf_selem_free_fields_rcu(rcu);
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else
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call_rcu(rcu, bpf_selem_free_fields_rcu);
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}
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static void bpf_selem_free_trace_rcu(struct rcu_head *rcu)
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{
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struct bpf_local_storage_elem *selem;
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@ -151,7 +130,6 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
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{
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struct bpf_local_storage_map *smap;
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bool free_local_storage;
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struct btf_record *rec;
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void *owner;
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smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
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@ -192,26 +170,11 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
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SDATA(selem))
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RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
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/* A different RCU callback is chosen whenever we need to free
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* additional fields in selem data before freeing selem.
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* bpf_local_storage_map_free only executes rcu_barrier to wait for RCU
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* callbacks when it has special fields, hence we can only conditionally
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* dereference smap, as by this time the map might have already been
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* freed without waiting for our call_rcu callback if it did not have
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* any special fields.
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*/
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rec = smap->map.record;
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if (!reuse_now) {
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if (!IS_ERR_OR_NULL(rec))
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call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_fields_trace_rcu);
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else
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call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu);
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} else {
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if (!IS_ERR_OR_NULL(rec))
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call_rcu(&selem->rcu, bpf_selem_free_fields_rcu);
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else
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kfree_rcu(selem, rcu);
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}
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bpf_obj_free_fields(smap->map.record, SDATA(selem)->data);
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if (!reuse_now)
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call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu);
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else
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kfree_rcu(selem, rcu);
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if (rcu_access_pointer(local_storage->smap) == smap)
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RCU_INIT_POINTER(local_storage->smap, NULL);
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@ -769,26 +732,6 @@ void bpf_local_storage_map_free(struct bpf_map *map,
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*/
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synchronize_rcu();
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/* Only delay freeing of smap, buckets are not needed anymore */
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kvfree(smap->buckets);
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/* When local storage has special fields, callbacks for
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* bpf_selem_free_fields_rcu and bpf_selem_free_fields_trace_rcu will
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* keep using the map BTF record, we need to execute an RCU barrier to
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* wait for them as the record will be freed right after our map_free
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* callback.
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*/
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if (!IS_ERR_OR_NULL(smap->map.record)) {
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rcu_barrier_tasks_trace();
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/* We cannot skip rcu_barrier() when rcu_trace_implies_rcu_gp()
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* is true, because while call_rcu invocation is skipped in that
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* case in bpf_selem_free_fields_trace_rcu (and all local
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* storage maps pass reuse_now = false), there can be
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* call_rcu callbacks based on reuse_now = true in the
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* while ((selem = ...)) loop above or when owner's free path
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* calls bpf_local_storage_unlink_nolock.
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*/
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rcu_barrier();
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}
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bpf_map_area_free(smap);
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}
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