]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/btree_cache.c
Update bcachefs sources to b964c6cba8 bcachefs: Change lockrestart_do() to always...
[bcachefs-tools-debian] / libbcachefs / btree_cache.c
index bb94fa2341eea839eca31128f1245b190d8244f8..cd0c5009e167b9f529fc8f9d0edfeaac460ff902 100644 (file)
@@ -1,22 +1,19 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include "bcachefs.h"
+#include "bkey_buf.h"
 #include "btree_cache.h"
 #include "btree_io.h"
 #include "btree_iter.h"
 #include "btree_locking.h"
 #include "debug.h"
+#include "error.h"
 
 #include <linux/prefetch.h>
 #include <linux/sched/mm.h>
 #include <trace/events/bcachefs.h>
 
-const char * const bch2_btree_ids[] = {
-#define x(kwd, val, name) name,
-       BCH_BTREE_IDS()
-#undef x
-       NULL
-};
+struct lock_class_key bch2_btree_node_lock_key;
 
 void bch2_recalc_btree_reserve(struct bch_fs *c)
 {
@@ -38,21 +35,21 @@ static inline unsigned btree_cache_can_free(struct btree_cache *bc)
        return max_t(int, 0, bc->used - bc->reserve);
 }
 
-static void __btree_node_data_free(struct bch_fs *c, struct btree *b)
+static void btree_node_data_free(struct bch_fs *c, struct btree *b)
 {
+       struct btree_cache *bc = &c->btree_cache;
+
        EBUG_ON(btree_node_write_in_flight(b));
 
        kvpfree(b->data, btree_bytes(c));
        b->data = NULL;
+#ifdef __KERNEL__
        vfree(b->aux_data);
+#else
+       munmap(b->aux_data, btree_aux_data_bytes(b));
+#endif
        b->aux_data = NULL;
-}
-
-static void btree_node_data_free(struct bch_fs *c, struct btree *b)
-{
-       struct btree_cache *bc = &c->btree_cache;
 
-       __btree_node_data_free(c, b);
        bc->used--;
        list_move(&b->list, &bc->freed);
 }
@@ -80,8 +77,13 @@ static int btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
        b->data = kvpmalloc(btree_bytes(c), gfp);
        if (!b->data)
                return -ENOMEM;
-
+#ifdef __KERNEL__
        b->aux_data = vmalloc_exec(btree_aux_data_bytes(b), gfp);
+#else
+       b->aux_data = mmap(NULL, btree_aux_data_bytes(b),
+                          PROT_READ|PROT_WRITE|PROT_EXEC,
+                          MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
+#endif
        if (!b->aux_data) {
                kvpfree(b->data, btree_bytes(c));
                b->data = NULL;
@@ -98,14 +100,14 @@ static struct btree *__btree_node_mem_alloc(struct bch_fs *c)
                return NULL;
 
        bkey_btree_ptr_init(&b->key);
-       six_lock_init(&b->c.lock);
+       __six_lock_init(&b->c.lock, "b->c.lock", &bch2_btree_node_lock_key);
        INIT_LIST_HEAD(&b->list);
        INIT_LIST_HEAD(&b->write_blocked);
        b->byte_order = ilog2(btree_bytes(c));
        return b;
 }
 
-static struct btree *btree_node_mem_alloc(struct bch_fs *c)
+struct btree *__bch2_btree_node_mem_alloc(struct bch_fs *c)
 {
        struct btree_cache *bc = &c->btree_cache;
        struct btree *b = __btree_node_mem_alloc(c);
@@ -151,6 +153,11 @@ int bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b,
        b->c.level      = level;
        b->c.btree_id   = id;
 
+       if (level)
+               six_lock_pcpu_alloc(&b->c.lock);
+       else
+               six_lock_pcpu_free_rcu(&b->c.lock);
+
        mutex_lock(&bc->lock);
        ret = __bch2_btree_node_hash_insert(bc, b);
        if (!ret)
@@ -179,6 +186,17 @@ static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
        int ret = 0;
 
        lockdep_assert_held(&bc->lock);
+wait_on_io:
+       if (b->flags & ((1U << BTREE_NODE_dirty)|
+                       (1U << BTREE_NODE_read_in_flight)|
+                       (1U << BTREE_NODE_write_in_flight))) {
+               if (!flush)
+                       return -ENOMEM;
+
+               /* XXX: waiting on IO with btree cache lock held */
+               bch2_btree_node_wait_on_read(b);
+               bch2_btree_node_wait_on_write(b);
+       }
 
        if (!six_trylock_intent(&b->c.lock))
                return -ENOMEM;
@@ -186,38 +204,40 @@ static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
        if (!six_trylock_write(&b->c.lock))
                goto out_unlock_intent;
 
+       /* recheck under lock */
+       if (b->flags & ((1U << BTREE_NODE_read_in_flight)|
+                       (1U << BTREE_NODE_write_in_flight))) {
+               if (!flush)
+                       goto out_unlock;
+               six_unlock_write(&b->c.lock);
+               six_unlock_intent(&b->c.lock);
+               goto wait_on_io;
+       }
+
        if (btree_node_noevict(b))
                goto out_unlock;
 
        if (!btree_node_may_write(b))
                goto out_unlock;
 
-       if (btree_node_dirty(b) &&
-           test_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags))
-               goto out_unlock;
-
-       if (btree_node_dirty(b) ||
-           btree_node_write_in_flight(b) ||
-           btree_node_read_in_flight(b)) {
-               if (!flush)
+       if (btree_node_dirty(b)) {
+               if (!flush ||
+                   test_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags))
                        goto out_unlock;
-
-               wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
-                              TASK_UNINTERRUPTIBLE);
-
                /*
                 * Using the underscore version because we don't want to compact
                 * bsets after the write, since this node is about to be evicted
                 * - unless btree verify mode is enabled, since it runs out of
                 * the post write cleanup:
                 */
-               if (verify_btree_ondisk(c))
+               if (bch2_verify_btree_ondisk)
                        bch2_btree_node_write(c, b, SIX_LOCK_intent);
                else
-                       __bch2_btree_node_write(c, b, SIX_LOCK_read);
+                       __bch2_btree_node_write(c, b, false);
 
-               /* wait for any in flight btree write */
-               btree_node_wait_on_io(b);
+               six_unlock_write(&b->c.lock);
+               six_unlock_intent(&b->c.lock);
+               goto wait_on_io;
        }
 out:
        if (b->hash_val && !ret)
@@ -254,7 +274,7 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
        unsigned long freed = 0;
        unsigned i, flags;
 
-       if (btree_shrinker_disabled(c))
+       if (bch2_btree_shrinker_disabled)
                return SHRINK_STOP;
 
        /* Return -1 if we can't do anything right now */
@@ -328,9 +348,9 @@ restart:
                        clear_btree_node_accessed(b);
        }
 
-       memalloc_nofs_restore(flags);
        mutex_unlock(&bc->lock);
 out:
+       memalloc_nofs_restore(flags);
        return (unsigned long) freed * btree_pages(c);
 }
 
@@ -341,7 +361,7 @@ static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
                                        btree_cache.shrink);
        struct btree_cache *bc = &c->btree_cache;
 
-       if (btree_shrinker_disabled(c))
+       if (bch2_btree_shrinker_disabled)
                return 0;
 
        return btree_cache_can_free(bc) * btree_pages(c);
@@ -360,12 +380,10 @@ void bch2_fs_btree_cache_exit(struct bch_fs *c)
        flags = memalloc_nofs_save();
        mutex_lock(&bc->lock);
 
-#ifdef CONFIG_BCACHEFS_DEBUG
        if (c->verify_data)
                list_move(&c->verify_data->list, &bc->live);
 
        kvpfree(c->verify_ondisk, btree_bytes(c));
-#endif
 
        for (i = 0; i < BTREE_ID_NR; i++)
                if (c->btree_roots[i].b)
@@ -381,14 +399,17 @@ void bch2_fs_btree_cache_exit(struct bch_fs *c)
 
                if (btree_node_dirty(b))
                        bch2_btree_complete_write(c, b, btree_current_write(b));
-               clear_btree_node_dirty(b);
+               clear_btree_node_dirty(c, b);
 
                btree_node_data_free(c, b);
        }
 
+       BUG_ON(atomic_read(&c->btree_cache.dirty));
+
        while (!list_empty(&bc->freed)) {
                b = list_first_entry(&bc->freed, struct btree, list);
                list_del(&b->list);
+               six_lock_pcpu_free(&b->c.lock);
                kfree(b);
        }
 
@@ -416,36 +437,20 @@ int bch2_fs_btree_cache_init(struct bch_fs *c)
        bch2_recalc_btree_reserve(c);
 
        for (i = 0; i < bc->reserve; i++)
-               if (!btree_node_mem_alloc(c)) {
+               if (!__bch2_btree_node_mem_alloc(c)) {
                        ret = -ENOMEM;
                        goto out;
                }
 
        list_splice_init(&bc->live, &bc->freeable);
 
-#ifdef CONFIG_BCACHEFS_DEBUG
        mutex_init(&c->verify_lock);
 
-       c->verify_ondisk = kvpmalloc(btree_bytes(c), GFP_KERNEL);
-       if (!c->verify_ondisk) {
-               ret = -ENOMEM;
-               goto out;
-       }
-
-       c->verify_data = btree_node_mem_alloc(c);
-       if (!c->verify_data) {
-               ret = -ENOMEM;
-               goto out;
-       }
-
-       list_del_init(&c->verify_data->list);
-#endif
-
        bc->shrink.count_objects        = bch2_btree_cache_count;
        bc->shrink.scan_objects         = bch2_btree_cache_scan;
        bc->shrink.seeks                = 4;
        bc->shrink.batch                = btree_pages(c) * 2;
-       register_shrinker(&bc->shrink);
+       ret = register_shrinker(&bc->shrink);
 out:
        pr_verbose_init(c->opts, "ret %i", ret);
        return ret;
@@ -582,6 +587,7 @@ got_node:
        }
 
        BUG_ON(btree_node_hashed(b));
+       BUG_ON(btree_node_dirty(b));
        BUG_ON(btree_node_write_in_flight(b));
 out:
        b->flags                = 0;
@@ -590,7 +596,8 @@ out:
        b->sib_u64s[0]          = 0;
        b->sib_u64s[1]          = 0;
        b->whiteout_u64s        = 0;
-       bch2_btree_keys_init(b, &c->expensive_debug_checks);
+       bch2_btree_keys_init(b);
+       set_btree_node_accessed(b);
 
        bch2_time_stats_update(&c->times[BCH_TIME_btree_node_mem_alloc],
                               start_time);
@@ -634,14 +641,17 @@ static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
 {
        struct btree_cache *bc = &c->btree_cache;
        struct btree *b;
+       u32 seq;
 
        BUG_ON(level + 1 >= BTREE_MAX_DEPTH);
        /*
         * Parent node must be locked, else we could read in a btree node that's
         * been freed:
         */
-       if (iter && !bch2_btree_node_relock(iter, level + 1))
+       if (iter && !bch2_btree_node_relock(iter, level + 1)) {
+               btree_trans_restart(iter->trans);
                return ERR_PTR(-EINTR);
+       }
 
        b = bch2_btree_node_mem_alloc(c);
        if (IS_ERR(b))
@@ -663,25 +673,32 @@ static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
                return NULL;
        }
 
-       /*
-        * Unlock before doing IO:
-        *
-        * XXX: ideally should be dropping all btree node locks here
-        */
-       if (iter && btree_node_read_locked(iter, level + 1))
-               btree_node_unlock(iter, level + 1);
-
-       bch2_btree_node_read(c, b, sync);
+       set_btree_node_read_in_flight(b);
 
        six_unlock_write(&b->c.lock);
+       seq = b->c.lock.state.seq;
+       six_unlock_intent(&b->c.lock);
 
-       if (!sync) {
-               six_unlock_intent(&b->c.lock);
+       /* Unlock before doing IO: */
+       if (iter && sync)
+               bch2_trans_unlock(iter->trans);
+
+       bch2_btree_node_read(c, b, sync);
+
+       if (!sync)
                return NULL;
+
+       if (iter &&
+           (!bch2_trans_relock(iter->trans) ||
+            !bch2_btree_iter_relock_intent(iter))) {
+               BUG_ON(!iter->trans->restarted);
+               return ERR_PTR(-EINTR);
        }
 
-       if (lock_type == SIX_LOCK_read)
-               six_lock_downgrade(&b->c.lock);
+       if (!six_relock_type(&b->c.lock, lock_type, seq)) {
+               btree_trans_restart(iter->trans);
+               return ERR_PTR(-EINTR);
+       }
 
        return b;
 }
@@ -694,6 +711,40 @@ static int lock_node_check_fn(struct six_lock *lock, void *p)
        return b->hash_val == btree_ptr_hash_val(k) ? 0 : -1;
 }
 
+static noinline void btree_bad_header(struct bch_fs *c, struct btree *b)
+{
+       char buf1[200], buf2[100], buf3[100];
+
+       if (!test_bit(BCH_FS_INITIAL_GC_DONE, &c->flags))
+               return;
+
+       bch2_bkey_val_to_text(&PBUF(buf1), c, bkey_i_to_s_c(&b->key));
+       bch2_bpos_to_text(&PBUF(buf2), b->data->min_key);
+       bch2_bpos_to_text(&PBUF(buf3), b->data->max_key);
+
+       bch2_fs_inconsistent(c, "btree node header doesn't match ptr\n"
+                            "btree %s level %u\n"
+                            "ptr: %s\n"
+                            "header: btree %s level %llu\n"
+                            "min %s max %s\n",
+                            bch2_btree_ids[b->c.btree_id], b->c.level,
+                            buf1,
+                            bch2_btree_ids[BTREE_NODE_ID(b->data)],
+                            BTREE_NODE_LEVEL(b->data),
+                            buf2, buf3);
+}
+
+static inline void btree_check_header(struct bch_fs *c, struct btree *b)
+{
+       if (b->c.btree_id != BTREE_NODE_ID(b->data) ||
+           b->c.level != BTREE_NODE_LEVEL(b->data) ||
+           bpos_cmp(b->data->max_key, b->key.k.p) ||
+           (b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
+            bpos_cmp(b->data->min_key,
+                     bkey_i_to_btree_ptr_v2(&b->key)->v.min_key)))
+               btree_bad_header(c, b);
+}
+
 /**
  * bch_btree_node_get - find a btree node in the cache and lock it, reading it
  * in from disk if necessary.
@@ -703,19 +754,23 @@ static int lock_node_check_fn(struct six_lock *lock, void *p)
  * The btree node will have either a read or a write lock held, depending on
  * the @write parameter.
  */
-struct btree *bch2_btree_node_get(struct bch_fs *c, struct btree_iter *iter,
+struct btree *bch2_btree_node_get(struct btree_trans *trans, struct btree_iter *iter,
                                  const struct bkey_i *k, unsigned level,
-                                 enum six_lock_type lock_type)
+                                 enum six_lock_type lock_type,
+                                 unsigned long trace_ip)
 {
+       struct bch_fs *c = trans->c;
        struct btree_cache *bc = &c->btree_cache;
        struct btree *b;
        struct bset_tree *t;
 
        EBUG_ON(level >= BTREE_MAX_DEPTH);
 
-       b = btree_node_mem_ptr(k);
-       if (b)
-               goto lock_node;
+       if (c->opts.btree_node_mem_ptr_optimization) {
+               b = btree_node_mem_ptr(k);
+               if (b)
+                       goto lock_node;
+       }
 retry:
        b = btree_cache_find(bc, k);
        if (unlikely(!b)) {
@@ -767,8 +822,8 @@ lock_node:
                        btree_node_unlock(iter, level + 1);
 
                if (!btree_node_lock(b, k->k.p, level, iter, lock_type,
-                                    lock_node_check_fn, (void *) k)) {
-                       if (b->hash_val != btree_ptr_hash_val(k))
+                                    lock_node_check_fn, (void *) k, trace_ip)) {
+                       if (!trans->restarted)
                                goto retry;
                        return ERR_PTR(-EINTR);
                }
@@ -780,14 +835,37 @@ lock_node:
                        if (bch2_btree_node_relock(iter, level + 1))
                                goto retry;
 
-                       trace_trans_restart_btree_node_reused(iter->trans->ip);
+                       trace_trans_restart_btree_node_reused(trans->ip,
+                                                             trace_ip,
+                                                             iter->btree_id,
+                                                             &iter->real_pos);
+                       btree_trans_restart(trans);
                        return ERR_PTR(-EINTR);
                }
        }
 
-       /* XXX: waiting on IO with btree locks held: */
-       wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
-                      TASK_UNINTERRUPTIBLE);
+       if (unlikely(btree_node_read_in_flight(b))) {
+               u32 seq = b->c.lock.state.seq;
+
+               six_unlock_type(&b->c.lock, lock_type);
+               bch2_trans_unlock(trans);
+
+               bch2_btree_node_wait_on_read(b);
+
+               /*
+                * should_be_locked is not set on this iterator yet, so we need
+                * to relock it specifically:
+                */
+               if (iter &&
+                   (!bch2_trans_relock(trans) ||
+                    !bch2_btree_iter_relock_intent(iter))) {
+                       BUG_ON(!trans->restarted);
+                       return ERR_PTR(-EINTR);
+               }
+
+               if (!six_relock_type(&b->c.lock, lock_type, seq))
+                       goto retry;
+       }
 
        prefetch(b->aux_data);
 
@@ -808,9 +886,9 @@ lock_node:
                return ERR_PTR(-EIO);
        }
 
-       EBUG_ON(b->c.btree_id != iter->btree_id ||
-               BTREE_NODE_LEVEL(b->data) != level ||
-               bkey_cmp(b->data->max_key, k->k.p));
+       EBUG_ON(b->c.btree_id != iter->btree_id);
+       EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
+       btree_check_header(c, b);
 
        return b;
 }
@@ -818,7 +896,8 @@ lock_node:
 struct btree *bch2_btree_node_get_noiter(struct bch_fs *c,
                                         const struct bkey_i *k,
                                         enum btree_id btree_id,
-                                        unsigned level)
+                                        unsigned level,
+                                        bool nofill)
 {
        struct btree_cache *bc = &c->btree_cache;
        struct btree *b;
@@ -827,12 +906,17 @@ struct btree *bch2_btree_node_get_noiter(struct bch_fs *c,
 
        EBUG_ON(level >= BTREE_MAX_DEPTH);
 
-       b = btree_node_mem_ptr(k);
-       if (b)
-               goto lock_node;
+       if (c->opts.btree_node_mem_ptr_optimization) {
+               b = btree_node_mem_ptr(k);
+               if (b)
+                       goto lock_node;
+       }
 retry:
        b = btree_cache_find(bc, k);
        if (unlikely(!b)) {
+               if (nofill)
+                       goto out;
+
                b = bch2_btree_node_fill(c, NULL, k, btree_id,
                                         level, SIX_LOCK_read, true);
 
@@ -840,8 +924,12 @@ retry:
                if (!b)
                        goto retry;
 
+               if (IS_ERR(b) &&
+                   !bch2_btree_cache_cannibalize_lock(c, NULL))
+                       goto retry;
+
                if (IS_ERR(b))
-                       return b;
+                       goto out;
        } else {
 lock_node:
                ret = six_lock_read(&b->c.lock, lock_node_check_fn, (void *) k);
@@ -857,8 +945,7 @@ lock_node:
        }
 
        /* XXX: waiting on IO with btree locks held: */
-       wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
-                      TASK_UNINTERRUPTIBLE);
+       __bch2_btree_node_wait_on_read(b);
 
        prefetch(b->aux_data);
 
@@ -876,143 +963,72 @@ lock_node:
 
        if (unlikely(btree_node_read_error(b))) {
                six_unlock_read(&b->c.lock);
-               return ERR_PTR(-EIO);
+               b = ERR_PTR(-EIO);
+               goto out;
        }
 
-       EBUG_ON(b->c.btree_id != btree_id ||
-               BTREE_NODE_LEVEL(b->data) != level ||
-               bkey_cmp(b->data->max_key, k->k.p));
-
+       EBUG_ON(b->c.btree_id != btree_id);
+       EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
+       btree_check_header(c, b);
+out:
+       bch2_btree_cache_cannibalize_unlock(c);
        return b;
 }
 
-struct btree *bch2_btree_node_get_sibling(struct bch_fs *c,
-                                         struct btree_iter *iter,
-                                         struct btree *b,
-                                         enum btree_node_sibling sib)
+int bch2_btree_node_prefetch(struct bch_fs *c, struct btree_iter *iter,
+                            const struct bkey_i *k,
+                            enum btree_id btree_id, unsigned level)
 {
-       struct btree_trans *trans = iter->trans;
-       struct btree *parent;
-       struct btree_node_iter node_iter;
-       struct bkey_packed *k;
-       BKEY_PADDED(k) tmp;
-       struct btree *ret = NULL;
-       unsigned level = b->c.level;
-
-       parent = btree_iter_node(iter, level + 1);
-       if (!parent)
-               return NULL;
-
-       /*
-        * There's a corner case where a btree_iter might have a node locked
-        * that is just outside its current pos - when
-        * bch2_btree_iter_set_pos_same_leaf() gets to the end of the node.
-        *
-        * But the lock ordering checks in __bch2_btree_node_lock() go off of
-        * iter->pos, not the node's key: so if the iterator is marked as
-        * needing to be traversed, we risk deadlock if we don't bail out here:
-        */
-       if (iter->uptodate >= BTREE_ITER_NEED_TRAVERSE)
-               return ERR_PTR(-EINTR);
-
-       if (!bch2_btree_node_relock(iter, level + 1)) {
-               ret = ERR_PTR(-EINTR);
-               goto out;
-       }
-
-       node_iter = iter->l[parent->c.level].iter;
-
-       k = bch2_btree_node_iter_peek_all(&node_iter, parent);
-       BUG_ON(bkey_cmp_left_packed(parent, k, &b->key.k.p));
-
-       k = sib == btree_prev_sib
-               ? bch2_btree_node_iter_prev(&node_iter, parent)
-               : (bch2_btree_node_iter_advance(&node_iter, parent),
-                  bch2_btree_node_iter_peek(&node_iter, parent));
-       if (!k)
-               goto out;
-
-       bch2_bkey_unpack(parent, &tmp.k, k);
-
-       ret = bch2_btree_node_get(c, iter, &tmp.k, level,
-                                 SIX_LOCK_intent);
-
-       if (PTR_ERR_OR_ZERO(ret) == -EINTR && !trans->nounlock) {
-               struct btree_iter *linked;
-
-               if (!bch2_btree_node_relock(iter, level + 1))
-                       goto out;
-
-               /*
-                * We might have got -EINTR because trylock failed, and we're
-                * holding other locks that would cause us to deadlock:
-                */
-               trans_for_each_iter(trans, linked)
-                       if (btree_iter_cmp(iter, linked) < 0)
-                               __bch2_btree_iter_unlock(linked);
-
-               if (sib == btree_prev_sib)
-                       btree_node_unlock(iter, level);
-
-               ret = bch2_btree_node_get(c, iter, &tmp.k, level,
-                                         SIX_LOCK_intent);
-
-               /*
-                * before btree_iter_relock() calls btree_iter_verify_locks():
-                */
-               if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
-                       btree_node_unlock(iter, level + 1);
-
-               if (!bch2_btree_node_relock(iter, level)) {
-                       btree_iter_set_dirty(iter, BTREE_ITER_NEED_RELOCK);
-
-                       if (!IS_ERR(ret)) {
-                               six_unlock_intent(&ret->c.lock);
-                               ret = ERR_PTR(-EINTR);
-                       }
-               }
-
-               bch2_trans_relock(trans);
-       }
-out:
-       if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
-               btree_node_unlock(iter, level + 1);
-
-       if (PTR_ERR_OR_ZERO(ret) == -EINTR)
-               bch2_btree_iter_upgrade(iter, level + 2);
-
-       BUG_ON(!IS_ERR(ret) && !btree_node_locked(iter, level));
-
-       if (!IS_ERR_OR_NULL(ret)) {
-               struct btree *n1 = ret, *n2 = b;
-
-               if (sib != btree_prev_sib)
-                       swap(n1, n2);
+       struct btree_cache *bc = &c->btree_cache;
+       struct btree *b;
 
-               BUG_ON(bkey_cmp(bkey_successor(n1->key.k.p),
-                               n2->data->min_key));
-       }
+       BUG_ON(iter && !btree_node_locked(iter, level + 1));
+       BUG_ON(level >= BTREE_MAX_DEPTH);
 
-       bch2_btree_trans_verify_locks(trans);
+       b = btree_cache_find(bc, k);
+       if (b)
+               return 0;
 
-       return ret;
+       b = bch2_btree_node_fill(c, iter, k, btree_id, level, SIX_LOCK_read, false);
+       return PTR_ERR_OR_ZERO(b);
 }
 
-void bch2_btree_node_prefetch(struct bch_fs *c, struct btree_iter *iter,
-                             const struct bkey_i *k, unsigned level)
+void bch2_btree_node_evict(struct bch_fs *c, const struct bkey_i *k)
 {
        struct btree_cache *bc = &c->btree_cache;
        struct btree *b;
 
-       BUG_ON(!btree_node_locked(iter, level + 1));
-       BUG_ON(level >= BTREE_MAX_DEPTH);
-
        b = btree_cache_find(bc, k);
-       if (b)
+       if (!b)
                return;
+wait_on_io:
+       /* not allowed to wait on io with btree locks held: */
+
+       /* XXX we're called from btree_gc which will be holding other btree
+        * nodes locked
+        * */
+       __bch2_btree_node_wait_on_read(b);
+       __bch2_btree_node_wait_on_write(b);
+
+       six_lock_intent(&b->c.lock, NULL, NULL);
+       six_lock_write(&b->c.lock, NULL, NULL);
+
+       if (btree_node_dirty(b)) {
+               __bch2_btree_node_write(c, b, false);
+               six_unlock_write(&b->c.lock);
+               six_unlock_intent(&b->c.lock);
+               goto wait_on_io;
+       }
+
+       BUG_ON(btree_node_dirty(b));
 
-       bch2_btree_node_fill(c, iter, k, iter->btree_id,
-                            level, SIX_LOCK_read, false);
+       mutex_lock(&bc->lock);
+       btree_node_data_free(c, b);
+       bch2_btree_node_hash_remove(bc, b);
+       mutex_unlock(&bc->lock);
+
+       six_unlock_write(&b->c.lock);
+       six_unlock_intent(&b->c.lock);
 }
 
 void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
@@ -1025,20 +1041,19 @@ void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
 
        bch2_btree_keys_stats(b, &stats);
 
-       pr_buf(out,
-              "l %u %llu:%llu - %llu:%llu:\n"
-              "    ptrs: ",
-              b->c.level,
-              b->data->min_key.inode,
-              b->data->min_key.offset,
-              b->data->max_key.inode,
-              b->data->max_key.offset);
+       pr_buf(out, "l %u ", b->c.level);
+       bch2_bpos_to_text(out, b->data->min_key);
+       pr_buf(out, " - ");
+       bch2_bpos_to_text(out, b->data->max_key);
+       pr_buf(out, ":\n"
+              "    ptrs: ");
        bch2_val_to_text(out, c, bkey_i_to_s_c(&b->key));
+
        pr_buf(out, "\n"
               "    format: u64s %u fields %u %u %u %u %u\n"
               "    unpack fn len: %u\n"
               "    bytes used %zu/%zu (%zu%% full)\n"
-              "    sib u64s: %u, %u (merge threshold %zu)\n"
+              "    sib u64s: %u, %u (merge threshold %u)\n"
               "    nr packed keys %u\n"
               "    nr unpacked keys %u\n"
               "    floats %zu\n"
@@ -1055,9 +1070,16 @@ void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
               b->nr.live_u64s * 100 / btree_max_u64s(c),
               b->sib_u64s[0],
               b->sib_u64s[1],
-              BTREE_FOREGROUND_MERGE_THRESHOLD(c),
+              c->btree_foreground_merge_threshold,
               b->nr.packed_keys,
               b->nr.unpacked_keys,
               stats.floats,
               stats.failed);
 }
+
+void bch2_btree_cache_to_text(struct printbuf *out, struct bch_fs *c)
+{
+       pr_buf(out, "nr nodes:\t\t%u\n", c->btree_cache.used);
+       pr_buf(out, "nr dirty:\t\t%u\n", atomic_read(&c->btree_cache.dirty));
+       pr_buf(out, "cannibalize lock:\t%p\n", c->btree_cache.alloc_lock);
+}