]> git.ipfire.org Git - thirdparty/kernel/linux.git/commitdiff
bcachefs: Rip out freelists from btree key cache
authorKent Overstreet <kent.overstreet@linux.dev>
Sun, 9 Jun 2024 02:32:40 +0000 (22:32 -0400)
committerKent Overstreet <kent.overstreet@linux.dev>
Mon, 9 Sep 2024 13:41:47 +0000 (09:41 -0400)
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
fs/bcachefs/btree_key_cache.c
fs/bcachefs/btree_key_cache_types.h
fs/bcachefs/btree_types.h

index fda7998734cbc1acd00e0c4a171ded929c9f8fda..dfaeb0810c5e4332e6ce5f0a1ecbc98d8c49dc04 100644 (file)
@@ -79,130 +79,39 @@ static bool bkey_cached_lock_for_evict(struct bkey_cached *ck)
        return true;
 }
 
-static void bkey_cached_evict(struct btree_key_cache *c,
+static bool bkey_cached_evict(struct btree_key_cache *c,
                              struct bkey_cached *ck)
 {
-       BUG_ON(rhashtable_remove_fast(&c->table, &ck->hash,
-                                     bch2_btree_key_cache_params));
-       memset(&ck->key, ~0, sizeof(ck->key));
-
-       atomic_long_dec(&c->nr_keys);
-}
-
-static void bkey_cached_free(struct btree_key_cache *bc,
-                            struct bkey_cached *ck)
-{
-       struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
-
-       BUG_ON(test_bit(BKEY_CACHED_DIRTY, &ck->flags));
-
-       ck->btree_trans_barrier_seq =
-               start_poll_synchronize_srcu(&c->btree_trans_barrier);
-
-       if (ck->c.lock.readers) {
-               list_move_tail(&ck->list, &bc->freed_pcpu);
-               bc->nr_freed_pcpu++;
-       } else {
-               list_move_tail(&ck->list, &bc->freed_nonpcpu);
-               bc->nr_freed_nonpcpu++;
+       bool ret = !rhashtable_remove_fast(&c->table, &ck->hash,
+                                     bch2_btree_key_cache_params);
+       if (ret) {
+               memset(&ck->key, ~0, sizeof(ck->key));
+               atomic_long_dec(&c->nr_keys);
        }
-       atomic_long_inc(&bc->nr_freed);
-
-       kfree(ck->k);
-       ck->k           = NULL;
-       ck->u64s        = 0;
 
-       six_unlock_write(&ck->c.lock);
-       six_unlock_intent(&ck->c.lock);
+       return ret;
 }
 
-#ifdef __KERNEL__
-static void __bkey_cached_move_to_freelist_ordered(struct btree_key_cache *bc,
-                                                  struct bkey_cached *ck)
+static void __bkey_cached_free(struct rcu_head *rcu)
 {
-       struct bkey_cached *pos;
-
-       bc->nr_freed_nonpcpu++;
+       struct bkey_cached *ck = container_of(rcu, struct bkey_cached, rcu);
 
-       list_for_each_entry_reverse(pos, &bc->freed_nonpcpu, list) {
-               if (ULONG_CMP_GE(ck->btree_trans_barrier_seq,
-                                pos->btree_trans_barrier_seq)) {
-                       list_move(&ck->list, &pos->list);
-                       return;
-               }
-       }
-
-       list_move(&ck->list, &bc->freed_nonpcpu);
+       kmem_cache_free(bch2_key_cache, ck);
 }
-#endif
-
-static void bkey_cached_move_to_freelist(struct btree_key_cache *bc,
-                                        struct bkey_cached *ck)
-{
-       BUG_ON(test_bit(BKEY_CACHED_DIRTY, &ck->flags));
-
-       if (!ck->c.lock.readers) {
-#ifdef __KERNEL__
-               struct btree_key_cache_freelist *f;
-               bool freed = false;
-
-               preempt_disable();
-               f = this_cpu_ptr(bc->pcpu_freed);
 
-               if (f->nr < ARRAY_SIZE(f->objs)) {
-                       f->objs[f->nr++] = ck;
-                       freed = true;
-               }
-               preempt_enable();
-
-               if (!freed) {
-                       mutex_lock(&bc->lock);
-                       preempt_disable();
-                       f = this_cpu_ptr(bc->pcpu_freed);
-
-                       while (f->nr > ARRAY_SIZE(f->objs) / 2) {
-                               struct bkey_cached *ck2 = f->objs[--f->nr];
-
-                               __bkey_cached_move_to_freelist_ordered(bc, ck2);
-                       }
-                       preempt_enable();
-
-                       __bkey_cached_move_to_freelist_ordered(bc, ck);
-                       mutex_unlock(&bc->lock);
-               }
-#else
-               mutex_lock(&bc->lock);
-               list_move_tail(&ck->list, &bc->freed_nonpcpu);
-               bc->nr_freed_nonpcpu++;
-               mutex_unlock(&bc->lock);
-#endif
-       } else {
-               mutex_lock(&bc->lock);
-               list_move_tail(&ck->list, &bc->freed_pcpu);
-               bc->nr_freed_pcpu++;
-               mutex_unlock(&bc->lock);
-       }
-}
-
-static void bkey_cached_free_fast(struct btree_key_cache *bc,
-                                 struct bkey_cached *ck)
+static void bkey_cached_free(struct btree_key_cache *bc,
+                            struct bkey_cached *ck)
 {
        struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
 
-       ck->btree_trans_barrier_seq =
-               start_poll_synchronize_srcu(&c->btree_trans_barrier);
-
-       list_del_init(&ck->list);
-       atomic_long_inc(&bc->nr_freed);
-
        kfree(ck->k);
        ck->k           = NULL;
        ck->u64s        = 0;
 
-       bkey_cached_move_to_freelist(bc, ck);
-
        six_unlock_write(&ck->c.lock);
        six_unlock_intent(&ck->c.lock);
+
+       call_srcu(&c->btree_trans_barrier, &ck->rcu, __bkey_cached_free);
 }
 
 static struct bkey_cached *__bkey_cached_alloc(unsigned key_u64s, gfp_t gfp)
@@ -222,78 +131,10 @@ static struct bkey_cached *__bkey_cached_alloc(unsigned key_u64s, gfp_t gfp)
 static struct bkey_cached *
 bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path, unsigned key_u64s)
 {
-       struct bch_fs *c = trans->c;
-       struct btree_key_cache *bc = &c->btree_key_cache;
-       struct bkey_cached *ck = NULL;
        bool pcpu_readers = btree_uses_pcpu_readers(path->btree_id);
        int ret;
 
-       if (!pcpu_readers) {
-#ifdef __KERNEL__
-               struct btree_key_cache_freelist *f;
-
-               preempt_disable();
-               f = this_cpu_ptr(bc->pcpu_freed);
-               if (f->nr)
-                       ck = f->objs[--f->nr];
-               preempt_enable();
-
-               if (!ck) {
-                       mutex_lock(&bc->lock);
-                       preempt_disable();
-                       f = this_cpu_ptr(bc->pcpu_freed);
-
-                       while (!list_empty(&bc->freed_nonpcpu) &&
-                              f->nr < ARRAY_SIZE(f->objs) / 2) {
-                               ck = list_last_entry(&bc->freed_nonpcpu, struct bkey_cached, list);
-                               list_del_init(&ck->list);
-                               bc->nr_freed_nonpcpu--;
-                               f->objs[f->nr++] = ck;
-                       }
-
-                       ck = f->nr ? f->objs[--f->nr] : NULL;
-                       preempt_enable();
-                       mutex_unlock(&bc->lock);
-               }
-#else
-               mutex_lock(&bc->lock);
-               if (!list_empty(&bc->freed_nonpcpu)) {
-                       ck = list_last_entry(&bc->freed_nonpcpu, struct bkey_cached, list);
-                       list_del_init(&ck->list);
-                       bc->nr_freed_nonpcpu--;
-               }
-               mutex_unlock(&bc->lock);
-#endif
-       } else {
-               mutex_lock(&bc->lock);
-               if (!list_empty(&bc->freed_pcpu)) {
-                       ck = list_last_entry(&bc->freed_pcpu, struct bkey_cached, list);
-                       list_del_init(&ck->list);
-                       bc->nr_freed_pcpu--;
-               }
-               mutex_unlock(&bc->lock);
-       }
-
-       if (ck) {
-               ret = btree_node_lock_nopath(trans, &ck->c, SIX_LOCK_intent, _THIS_IP_);
-               if (unlikely(ret)) {
-                       bkey_cached_move_to_freelist(bc, ck);
-                       return ERR_PTR(ret);
-               }
-
-               btree_path_cached_set(trans, path, ck, BTREE_NODE_INTENT_LOCKED);
-
-               ret = bch2_btree_node_lock_write(trans, path, &ck->c);
-               if (unlikely(ret)) {
-                       btree_node_unlock(trans, path, 0);
-                       bkey_cached_move_to_freelist(bc, ck);
-                       return ERR_PTR(ret);
-               }
-
-               return ck;
-       }
-
-       ck = allocate_dropping_locks(trans, ret,
+       struct bkey_cached *ck = allocate_dropping_locks(trans, ret,
                                     __bkey_cached_alloc(key_u64s, _gfp));
        if (ret) {
                if (ck)
@@ -305,7 +146,6 @@ bkey_cached_alloc(struct btree_trans *trans, struct btree_path *path, unsigned k
        if (!ck)
                return NULL;
 
-       INIT_LIST_HEAD(&ck->list);
        bch2_btree_lock_init(&ck->c, pcpu_readers ? SIX_LOCK_INIT_PCPU : 0);
 
        ck->c.cached = true;
@@ -322,21 +162,21 @@ bkey_cached_reuse(struct btree_key_cache *c)
        struct bkey_cached *ck;
        unsigned i;
 
-       mutex_lock(&c->lock);
        rcu_read_lock();
        tbl = rht_dereference_rcu(c->table.tbl, &c->table);
        for (i = 0; i < tbl->size; i++)
                rht_for_each_entry_rcu(ck, pos, tbl, i, hash) {
                        if (!test_bit(BKEY_CACHED_DIRTY, &ck->flags) &&
                            bkey_cached_lock_for_evict(ck)) {
-                               bkey_cached_evict(c, ck);
-                               goto out;
+                               if (bkey_cached_evict(c, ck))
+                                       goto out;
+                               six_unlock_write(&ck->c.lock);
+                               six_unlock_intent(&ck->c.lock);
                        }
                }
        ck = NULL;
 out:
        rcu_read_unlock();
-       mutex_unlock(&c->lock);
        return ck;
 }
 
@@ -415,7 +255,7 @@ static int btree_key_cache_create(struct btree_trans *trans, struct btree_path *
        path->uptodate = BTREE_ITER_UPTODATE;
        return 0;
 err:
-       bkey_cached_free_fast(bc, ck);
+       bkey_cached_free(bc, ck);
        mark_btree_node_locked_noreset(path, 0, BTREE_NODE_UNLOCKED);
 
        return ret;
@@ -611,8 +451,12 @@ evict:
                }
 
                mark_btree_node_locked_noreset(path, 0, BTREE_NODE_UNLOCKED);
-               bkey_cached_evict(&c->btree_key_cache, ck);
-               bkey_cached_free_fast(&c->btree_key_cache, ck);
+               if (bkey_cached_evict(&c->btree_key_cache, ck)) {
+                       bkey_cached_free(&c->btree_key_cache, ck);
+               } else {
+                       six_unlock_write(&ck->c.lock);
+                       six_unlock_intent(&ck->c.lock);
+               }
        }
 out:
        bch2_trans_iter_exit(trans, &b_iter);
@@ -722,7 +566,7 @@ void bch2_btree_key_cache_drop(struct btree_trans *trans,
        }
 
        bkey_cached_evict(bc, ck);
-       bkey_cached_free_fast(bc, ck);
+       bkey_cached_free(bc, ck);
 
        mark_btree_node_locked(trans, path, 0, BTREE_NODE_UNLOCKED);
        btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
@@ -735,48 +579,14 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
        struct bch_fs *c = shrink->private_data;
        struct btree_key_cache *bc = &c->btree_key_cache;
        struct bucket_table *tbl;
-       struct bkey_cached *ck, *t;
+       struct bkey_cached *ck;
        size_t scanned = 0, freed = 0, nr = sc->nr_to_scan;
-       unsigned start, flags;
+       unsigned iter, start;
        int srcu_idx;
 
-       mutex_lock(&bc->lock);
-       bc->requested_to_free += sc->nr_to_scan;
-
        srcu_idx = srcu_read_lock(&c->btree_trans_barrier);
-       flags = memalloc_nofs_save();
-
-       /*
-        * Newest freed entries are at the end of the list - once we hit one
-        * that's too new to be freed, we can bail out:
-        */
-       list_for_each_entry_safe(ck, t, &bc->freed_nonpcpu, list) {
-               if (!poll_state_synchronize_srcu(&c->btree_trans_barrier,
-                                                ck->btree_trans_barrier_seq))
-                       break;
-
-               list_del(&ck->list);
-               six_lock_exit(&ck->c.lock);
-               kmem_cache_free(bch2_key_cache, ck);
-               atomic_long_dec(&bc->nr_freed);
-               bc->nr_freed_nonpcpu--;
-               bc->freed++;
-       }
-
-       list_for_each_entry_safe(ck, t, &bc->freed_pcpu, list) {
-               if (!poll_state_synchronize_srcu(&c->btree_trans_barrier,
-                                                ck->btree_trans_barrier_seq))
-                       break;
-
-               list_del(&ck->list);
-               six_lock_exit(&ck->c.lock);
-               kmem_cache_free(bch2_key_cache, ck);
-               atomic_long_dec(&bc->nr_freed);
-               bc->nr_freed_pcpu--;
-               bc->freed++;
-       }
-
        rcu_read_lock();
+
        tbl = rht_dereference_rcu(bc->table.tbl, &bc->table);
 
        /*
@@ -792,17 +602,18 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
                return SHRINK_STOP;
        }
 
-       if (bc->shrink_iter >= tbl->size)
-               bc->shrink_iter = 0;
-       start = bc->shrink_iter;
+       iter = bc->shrink_iter;
+       if (iter >= tbl->size)
+               iter = 0;
+       start = iter;
 
        do {
                struct rhash_head *pos, *next;
 
-               pos = rht_ptr_rcu(&tbl->buckets[bc->shrink_iter]);
+               pos = rht_ptr_rcu(&tbl->buckets[iter]);
 
                while (!rht_is_a_nulls(pos)) {
-                       next = rht_dereference_bucket_rcu(pos->next, tbl, bc->shrink_iter);
+                       next = rht_dereference_bucket_rcu(pos->next, tbl, iter);
                        ck = container_of(pos, struct bkey_cached, hash);
 
                        if (test_bit(BKEY_CACHED_DIRTY, &ck->flags)) {
@@ -812,29 +623,31 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
                                bc->skipped_accessed++;
                        } else if (!bkey_cached_lock_for_evict(ck)) {
                                bc->skipped_lock_fail++;
-                       } else {
-                               bkey_cached_evict(bc, ck);
+                       } else if (bkey_cached_evict(bc, ck)) {
                                bkey_cached_free(bc, ck);
-                               bc->moved_to_freelist++;
+                               bc->freed++;
                                freed++;
+                       } else {
+                               six_unlock_write(&ck->c.lock);
+                               six_unlock_intent(&ck->c.lock);
                        }
 
                        scanned++;
                        if (scanned >= nr)
-                               break;
+                               goto out;
 
                        pos = next;
                }
 
-               bc->shrink_iter++;
-               if (bc->shrink_iter >= tbl->size)
-                       bc->shrink_iter = 0;
-       } while (scanned < nr && bc->shrink_iter != start);
+               iter++;
+               if (iter >= tbl->size)
+                       iter = 0;
+       } while (scanned < nr && iter != start);
+out:
+       bc->shrink_iter = iter;
 
        rcu_read_unlock();
-       memalloc_nofs_restore(flags);
        srcu_read_unlock(&c->btree_trans_barrier, srcu_idx);
-       mutex_unlock(&bc->lock);
 
        return freed;
 }
@@ -862,18 +675,13 @@ void bch2_fs_btree_key_cache_exit(struct btree_key_cache *bc)
 {
        struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
        struct bucket_table *tbl;
-       struct bkey_cached *ck, *n;
+       struct bkey_cached *ck;
        struct rhash_head *pos;
        LIST_HEAD(items);
        unsigned i;
-#ifdef __KERNEL__
-       int cpu;
-#endif
 
        shrinker_free(bc->shrink);
 
-       mutex_lock(&bc->lock);
-
        /*
         * The loop is needed to guard against racing with rehash:
         */
@@ -892,44 +700,14 @@ void bch2_fs_btree_key_cache_exit(struct btree_key_cache *bc)
                        for (i = 0; i < tbl->size; i++)
                                while (pos = rht_ptr_rcu(&tbl->buckets[i]), !rht_is_a_nulls(pos)) {
                                        ck = container_of(pos, struct bkey_cached, hash);
-                                       bkey_cached_evict(bc, ck);
-                                       list_add(&ck->list, &items);
+                                       BUG_ON(!bkey_cached_evict(bc, ck));
+                                       kfree(ck->k);
+                                       kmem_cache_free(bch2_key_cache, ck);
                                }
                }
                rcu_read_unlock();
        }
 
-#ifdef __KERNEL__
-       if (bc->pcpu_freed) {
-               for_each_possible_cpu(cpu) {
-                       struct btree_key_cache_freelist *f =
-                               per_cpu_ptr(bc->pcpu_freed, cpu);
-
-                       for (i = 0; i < f->nr; i++) {
-                               ck = f->objs[i];
-                               list_add(&ck->list, &items);
-                       }
-               }
-       }
-#endif
-
-       BUG_ON(list_count_nodes(&bc->freed_pcpu) != bc->nr_freed_pcpu);
-       BUG_ON(list_count_nodes(&bc->freed_nonpcpu) != bc->nr_freed_nonpcpu);
-
-       list_splice(&bc->freed_pcpu,    &items);
-       list_splice(&bc->freed_nonpcpu, &items);
-
-       mutex_unlock(&bc->lock);
-
-       list_for_each_entry_safe(ck, n, &items, list) {
-               cond_resched();
-
-               list_del(&ck->list);
-               kfree(ck->k);
-               six_lock_exit(&ck->c.lock);
-               kmem_cache_free(bch2_key_cache, ck);
-       }
-
        if (atomic_long_read(&bc->nr_dirty) &&
            !bch2_journal_error(&c->journal) &&
            test_bit(BCH_FS_was_rw, &c->flags))
@@ -942,15 +720,10 @@ void bch2_fs_btree_key_cache_exit(struct btree_key_cache *bc)
 
        if (bc->table_init_done)
                rhashtable_destroy(&bc->table);
-
-       free_percpu(bc->pcpu_freed);
 }
 
 void bch2_fs_btree_key_cache_init_early(struct btree_key_cache *c)
 {
-       mutex_init(&c->lock);
-       INIT_LIST_HEAD(&c->freed_pcpu);
-       INIT_LIST_HEAD(&c->freed_nonpcpu);
 }
 
 int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
@@ -958,12 +731,6 @@ int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
        struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
        struct shrinker *shrink;
 
-#ifdef __KERNEL__
-       bc->pcpu_freed = alloc_percpu(struct btree_key_cache_freelist);
-       if (!bc->pcpu_freed)
-               return -BCH_ERR_ENOMEM_fs_btree_cache_init;
-#endif
-
        if (rhashtable_init(&bc->table, &bch2_btree_key_cache_params))
                return -BCH_ERR_ENOMEM_fs_btree_cache_init;
 
@@ -984,45 +751,19 @@ int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
 
 void bch2_btree_key_cache_to_text(struct printbuf *out, struct btree_key_cache *bc)
 {
-       struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
-
        printbuf_tabstop_push(out, 24);
        printbuf_tabstop_push(out, 12);
 
-       unsigned flags = memalloc_nofs_save();
-       mutex_lock(&bc->lock);
        prt_printf(out, "keys:\t%lu\r\n",               atomic_long_read(&bc->nr_keys));
        prt_printf(out, "dirty:\t%lu\r\n",              atomic_long_read(&bc->nr_dirty));
-       prt_printf(out, "freelist:\t%lu\r\n",           atomic_long_read(&bc->nr_freed));
-       prt_printf(out, "nonpcpu freelist:\t%zu\r\n",   bc->nr_freed_nonpcpu);
-       prt_printf(out, "pcpu freelist:\t%zu\r\n",      bc->nr_freed_pcpu);
+       prt_printf(out, "table size:\t%u\r\n",          bc->table.tbl->size);
 
        prt_printf(out, "\nshrinker:\n");
        prt_printf(out, "requested_to_free:\t%lu\r\n",  bc->requested_to_free);
        prt_printf(out, "freed:\t%lu\r\n",              bc->freed);
-       prt_printf(out, "moved_to_freelist:\t%lu\r\n",  bc->moved_to_freelist);
        prt_printf(out, "skipped_dirty:\t%lu\r\n",      bc->skipped_dirty);
        prt_printf(out, "skipped_accessed:\t%lu\r\n",   bc->skipped_accessed);
        prt_printf(out, "skipped_lock_fail:\t%lu\r\n",  bc->skipped_lock_fail);
-
-       prt_printf(out, "srcu seq:\t%lu\r\n",           get_state_synchronize_srcu(&c->btree_trans_barrier));
-
-       struct bkey_cached *ck;
-       unsigned iter = 0;
-       list_for_each_entry(ck, &bc->freed_nonpcpu, list) {
-               prt_printf(out, "freed_nonpcpu:\t%lu\r\n", ck->btree_trans_barrier_seq);
-               if (++iter > 10)
-                       break;
-       }
-
-       iter = 0;
-       list_for_each_entry(ck, &bc->freed_pcpu, list) {
-               prt_printf(out, "freed_pcpu:\t%lu\r\n", ck->btree_trans_barrier_seq);
-               if (++iter > 10)
-                       break;
-       }
-       mutex_unlock(&bc->lock);
-       memalloc_flags_restore(flags);
 }
 
 void bch2_btree_key_cache_exit(void)
index 237e8bb3ac407f1273ee781069b945fade71f0cb..e026c65f54e150943e4cdaf2d0bdf9e906ce154b 100644 (file)
@@ -2,33 +2,19 @@
 #ifndef _BCACHEFS_BTREE_KEY_CACHE_TYPES_H
 #define _BCACHEFS_BTREE_KEY_CACHE_TYPES_H
 
-struct btree_key_cache_freelist {
-       struct bkey_cached      *objs[16];
-       unsigned                nr;
-};
-
 struct btree_key_cache {
-       struct mutex            lock;
        struct rhashtable       table;
        bool                    table_init_done;
 
-       struct list_head        freed_pcpu;
-       size_t                  nr_freed_pcpu;
-       struct list_head        freed_nonpcpu;
-       size_t                  nr_freed_nonpcpu;
-
        struct shrinker         *shrink;
        unsigned                shrink_iter;
-       struct btree_key_cache_freelist __percpu *pcpu_freed;
 
-       atomic_long_t           nr_freed;
        atomic_long_t           nr_keys;
        atomic_long_t           nr_dirty;
 
        /* shrinker stats */
        unsigned long           requested_to_free;
        unsigned long           freed;
-       unsigned long           moved_to_freelist;
        unsigned long           skipped_dirty;
        unsigned long           skipped_accessed;
        unsigned long           skipped_lock_fail;
index b256b2a20a4f86017107c4bea0b06f98b3d52e26..bca56b6359e771c2bada2bcb336c927b02783a3b 100644 (file)
@@ -386,17 +386,17 @@ struct bkey_cached {
        struct btree_bkey_cached_common c;
 
        unsigned long           flags;
-       unsigned long           btree_trans_barrier_seq;
        u16                     u64s;
        struct bkey_cached_key  key;
 
        struct rhash_head       hash;
-       struct list_head        list;
 
        struct journal_entry_pin journal;
        u64                     seq;
 
        struct bkey_i           *k;
+
+       struct rcu_head         rcu;
 };
 
 static inline struct bpos btree_node_pos(struct btree_bkey_cached_common *b)