bcachefs: bch2_bkey_get_iter() helpers

Introduce new helpers for a common pattern:

  bch2_trans_iter_init();
  bch2_btree_iter_peek_slot();

 - bch2_bkey_get_iter_type() returns -ENOENT if it doesn't find a key of
   the correct type
 - bch2_bkey_get_val_typed() copies the val out of the btree to a
   (typically stack allocated) variable; it handles the case where the
   value in the btree is smaller than the current version of the type,
   zeroing out the remainder.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

15 files changed, 162 insertions, 218 deletions

diff --git a/fs/bcachefs/alloc_background.c b/fs/bcachefs/alloc_background.c
index 968b6103e979..b938c37cb0fe 100644
--- a/fs/bcachefs/alloc_background.c
+++ b/fs/bcachefs/alloc_background.c
@@ -540,14 +540,13 @@ bch2_trans_start_alloc_update(struct btree_trans *trans, struct btree_iter *iter
 	struct bkey_i_alloc_v4 *a;
 	int ret;
 
-	bch2_trans_iter_init(trans, iter, BTREE_ID_alloc, pos,
+	k = bch2_bkey_get_iter(trans, iter, BTREE_ID_alloc, pos,
 			     BTREE_ITER_WITH_UPDATES|
 			     BTREE_ITER_CACHED|
 			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(iter);
 	ret = bkey_err(k);
 	if (unlikely(ret))
-		goto err;
+		return ERR_PTR(ret);
 
 	a = bch2_alloc_to_v4_mut_inlined(trans, k);
 	ret = PTR_ERR_OR_ZERO(a);
@@ -789,13 +788,12 @@ static int bch2_bucket_do_index(struct btree_trans *trans,
 		return 0;
 	}
 
-	bch2_trans_iter_init(trans, &iter, btree,
+	old = bch2_bkey_get_iter(trans, &iter, btree,
 			     bkey_start_pos(&k->k),
 			     BTREE_ITER_INTENT);
-	old = bch2_btree_iter_peek_slot(&iter);
 	ret = bkey_err(old);
 	if (ret)
-		goto err;
+		return ret;
 
 	if (ca->mi.freespace_initialized &&
 	    test_bit(BCH_FS_CHECK_ALLOC_DONE, &c->flags) &&
@@ -833,13 +831,12 @@ static noinline int bch2_bucket_gen_update(struct btree_trans *trans,
 	if (ret)
 		return ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_bucket_gens, pos,
-			     BTREE_ITER_INTENT|
-			     BTREE_ITER_WITH_UPDATES);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_bucket_gens, pos,
+			       BTREE_ITER_INTENT|
+			       BTREE_ITER_WITH_UPDATES);
 	ret = bkey_err(k);
 	if (ret)
-		goto err;
+		return ret;
 
 	if (k.k->type != KEY_TYPE_bucket_gens) {
 		bkey_bucket_gens_init(&g->k_i);
@@ -851,7 +848,6 @@ static noinline int bch2_bucket_gen_update(struct btree_trans *trans,
 	g->v.gens[offset] = gen;
 
 	ret = bch2_trans_update(trans, &iter, &g->k_i, 0);
-err:
 	bch2_trans_iter_exit(trans, &iter);
 	return ret;
 }
@@ -1312,18 +1308,16 @@ static int bch2_check_discard_freespace_key(struct btree_trans *trans,
 	pos.offset &= ~(~0ULL << 56);
 	genbits = iter->pos.offset & (~0ULL << 56);
 
-	bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc, pos, 0);
+	alloc_k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc, pos, 0);
+	ret = bkey_err(alloc_k);
+	if (ret)
+		return ret;
 
 	if (fsck_err_on(!bch2_dev_bucket_exists(c, pos), c,
 			"entry in %s btree for nonexistant dev:bucket %llu:%llu",
 			bch2_btree_ids[iter->btree_id], pos.inode, pos.offset))
 		goto delete;
 
-	alloc_k = bch2_btree_iter_peek_slot(&alloc_iter);
-	ret = bkey_err(alloc_k);
-	if (ret)
-		goto err;
-
 	a = bch2_alloc_to_v4(alloc_k, &a_convert);
 
 	if (fsck_err_on(a->data_type != state ||
@@ -1336,7 +1330,6 @@ static int bch2_check_discard_freespace_key(struct btree_trans *trans,
 			genbits >> 56, alloc_freespace_genbits(*a) >> 56))
 		goto delete;
 out:
-err:
 fsck_err:
 	bch2_trans_iter_exit(trans, &alloc_iter);
 	printbuf_exit(&buf);
@@ -1525,7 +1518,7 @@ static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
 	struct btree_iter lru_iter;
 	struct bch_alloc_v4 a_convert;
 	const struct bch_alloc_v4 *a;
-	struct bkey_s_c alloc_k, k;
+	struct bkey_s_c alloc_k, lru_k;
 	struct printbuf buf = PRINTBUF;
 	int ret;
 
@@ -1542,21 +1535,20 @@ static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
 	if (a->data_type != BCH_DATA_cached)
 		return 0;
 
-	bch2_trans_iter_init(trans, &lru_iter, BTREE_ID_lru,
+	lru_k = bch2_bkey_get_iter(trans, &lru_iter, BTREE_ID_lru,
 			     lru_pos(alloc_k.k->p.inode,
 				     bucket_to_u64(alloc_k.k->p),
 				     a->io_time[READ]), 0);
-	k = bch2_btree_iter_peek_slot(&lru_iter);
-	ret = bkey_err(k);
+	ret = bkey_err(lru_k);
 	if (ret)
-		goto err;
+		return ret;
 
 	if (fsck_err_on(!a->io_time[READ], c,
 			"cached bucket with read_time 0\n"
 			"  %s",
 		(printbuf_reset(&buf),
 		 bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf)) ||
-	    fsck_err_on(k.k->type != KEY_TYPE_set, c,
+	    fsck_err_on(lru_k.k->type != KEY_TYPE_set, c,
 			"missing lru entry\n"
 			"  %s",
 			(printbuf_reset(&buf),
@@ -1645,10 +1637,9 @@ static int bch2_discard_one_bucket(struct btree_trans *trans,
 		goto out;
 	}
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
-			     need_discard_iter->pos,
-			     BTREE_ITER_CACHED);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_alloc,
+			       need_discard_iter->pos,
+			       BTREE_ITER_CACHED);
 	ret = bkey_err(k);
 	if (ret)
 		goto out;
diff --git a/fs/bcachefs/alloc_foreground.c b/fs/bcachefs/alloc_foreground.c
index 368355de5f26..ec77601ebd0c 100644
--- a/fs/bcachefs/alloc_foreground.c
+++ b/fs/bcachefs/alloc_foreground.c
@@ -303,8 +303,9 @@ static struct open_bucket *try_alloc_bucket(struct btree_trans *trans, struct bc
 		goto err;
 	}
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc, POS(ca->dev_idx, b), BTREE_ITER_CACHED);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter,
+			       BTREE_ID_alloc, POS(ca->dev_idx, b),
+			       BTREE_ITER_CACHED);
 	ret = bkey_err(k);
 	if (ret) {
 		ob = ERR_PTR(ret);
diff --git a/fs/bcachefs/backpointers.c b/fs/bcachefs/backpointers.c
index e8666c3ed465..e9ae623cf4a8 100644
--- a/fs/bcachefs/backpointers.c
+++ b/fs/bcachefs/backpointers.c
@@ -158,12 +158,11 @@ int bch2_bucket_backpointer_mod_nowritebuffer(struct btree_trans *trans,
 		set_bkey_val_u64s(&bp_k->k, 0);
 	}
 
-	bch2_trans_iter_init(trans, &bp_iter, BTREE_ID_backpointers,
-			     bp_k->k.p,
-			     BTREE_ITER_INTENT|
-			     BTREE_ITER_SLOTS|
-			     BTREE_ITER_WITH_UPDATES);
-	k = bch2_btree_iter_peek_slot(&bp_iter);
+	k = bch2_bkey_get_iter(trans, &bp_iter, BTREE_ID_backpointers,
+			       bp_k->k.p,
+			       BTREE_ITER_INTENT|
+			       BTREE_ITER_SLOTS|
+			       BTREE_ITER_WITH_UPDATES);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
@@ -202,9 +201,8 @@ int bch2_get_next_backpointer(struct btree_trans *trans,
 		goto done;
 
 	if (gen >= 0) {
-		bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc,
-				     bucket, BTREE_ITER_CACHED|iter_flags);
-		k = bch2_btree_iter_peek_slot(&alloc_iter);
+		k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc,
+				       bucket, BTREE_ITER_CACHED|iter_flags);
 		ret = bkey_err(k);
 		if (ret)
 			goto out;
@@ -381,10 +379,8 @@ static int bch2_check_btree_backpointer(struct btree_trans *trans, struct btree_
 
 	ca = bch_dev_bkey_exists(c, k.k->p.inode);
 
-	bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc,
-			     bp_pos_to_bucket(c, k.k->p), 0);
-
-	alloc_k = bch2_btree_iter_peek_slot(&alloc_iter);
+	alloc_k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc,
+				     bp_pos_to_bucket(c, k.k->p), 0);
 	ret = bkey_err(alloc_k);
 	if (ret)
 		goto out;
@@ -442,10 +438,9 @@ static int check_bp_exists(struct btree_trans *trans,
 	if (!bch2_dev_bucket_exists(c, bucket))
 		goto missing;
 
-	bch2_trans_iter_init(trans, &bp_iter, BTREE_ID_backpointers,
-			     bucket_pos_to_bp(c, bucket, bp.bucket_offset),
-			     0);
-	bp_k = bch2_btree_iter_peek_slot(&bp_iter);
+	bp_k = bch2_bkey_get_iter(trans, &bp_iter, BTREE_ID_backpointers,
+				  bucket_pos_to_bp(c, bucket, bp.bucket_offset),
+				  0);
 	ret = bkey_err(bp_k);
 	if (ret)
 		goto err;
diff --git a/fs/bcachefs/btree_iter.h b/fs/bcachefs/btree_iter.h
index 112e89943137..f257f58d3060 100644
--- a/fs/bcachefs/btree_iter.h
+++ b/fs/bcachefs/btree_iter.h
@@ -483,6 +483,62 @@ static inline void *bch2_trans_kmalloc_nomemzero(struct btree_trans *trans, size
 	}
 }
 
+static inline struct bkey_s_c __bch2_bkey_get_iter(struct btree_trans *trans,
+				struct btree_iter *iter,
+				unsigned btree_id, struct bpos pos,
+				unsigned flags, unsigned type)
+{
+	struct bkey_s_c k;
+
+	bch2_trans_iter_init(trans, iter, btree_id, pos, flags);
+	k = bch2_btree_iter_peek_slot(iter);
+
+	if (!bkey_err(k) && type && k.k->type != type)
+		k = bkey_s_c_err(-ENOENT);
+	if (unlikely(bkey_err(k)))
+		bch2_trans_iter_exit(trans, iter);
+	return k;
+}
+
+static inline struct bkey_s_c bch2_bkey_get_iter(struct btree_trans *trans,
+				struct btree_iter *iter,
+				unsigned btree_id, struct bpos pos,
+				unsigned flags)
+{
+	return __bch2_bkey_get_iter(trans, iter, btree_id, pos, flags, 0);
+}
+
+#define bch2_bkey_get_iter_typed(_trans, _iter, _btree_id, _pos, _flags, _type)\
+	bkey_s_c_to_##_type(__bch2_bkey_get_iter(_trans, _iter,			\
+				       _btree_id, _pos, _flags, KEY_TYPE_##_type))
+
+static inline int __bch2_bkey_get_val_typed(struct btree_trans *trans,
+				unsigned btree_id, struct bpos pos,
+				unsigned flags, unsigned type,
+				unsigned val_size, void *val)
+{
+	struct btree_iter iter;
+	struct bkey_s_c k;
+	int ret;
+
+	k = __bch2_bkey_get_iter(trans, &iter, btree_id, pos, flags, type);
+	ret = bkey_err(k);
+	if (!ret) {
+		unsigned b = min_t(unsigned, bkey_val_bytes(k.k), val_size);
+
+		memcpy(val, k.v, b);
+		if (unlikely(b < sizeof(*val)))
+			memset((void *) val + b, 0, sizeof(*val) - b);
+		bch2_trans_iter_exit(trans, &iter);
+	}
+
+	return ret;
+}
+
+#define bch2_bkey_get_val_typed(_trans, _btree_id, _pos, _flags, _type, _val)\
+	__bch2_bkey_get_val_typed(_trans, _btree_id, _pos, _flags,	\
+				  KEY_TYPE_##_type, sizeof(*_val), _val)
+
 static inline struct bkey_i *bch2_bkey_make_mut(struct btree_trans *trans, struct bkey_s_c k)
 {
 	struct bkey_i *mut = bch2_trans_kmalloc_nomemzero(trans, bkey_bytes(k.k));
diff --git a/fs/bcachefs/btree_key_cache.c b/fs/bcachefs/btree_key_cache.c
index a483bd23a336..727ea2d0e58d 100644
--- a/fs/bcachefs/btree_key_cache.c
+++ b/fs/bcachefs/btree_key_cache.c
@@ -386,10 +386,9 @@ static int btree_key_cache_fill(struct btree_trans *trans,
 	struct bkey_i *new_k = NULL;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, ck->key.btree_id, ck->key.pos,
-			     BTREE_ITER_KEY_CACHE_FILL|
-			     BTREE_ITER_CACHED_NOFILL);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, ck->key.btree_id, ck->key.pos,
+			       BTREE_ITER_KEY_CACHE_FILL|
+			       BTREE_ITER_CACHED_NOFILL);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
diff --git a/fs/bcachefs/data_update.c b/fs/bcachefs/data_update.c
index cffb3c14d539..c709538ce9c2 100644
--- a/fs/bcachefs/data_update.c
+++ b/fs/bcachefs/data_update.c
@@ -57,10 +57,9 @@ static int insert_snapshot_whiteouts(struct btree_trans *trans,
 
 			whiteout_pos.snapshot = k.k->p.snapshot;
 
-			bch2_trans_iter_init(trans, &iter2, id, whiteout_pos,
-					     BTREE_ITER_NOT_EXTENTS|
-					     BTREE_ITER_INTENT);
-			k2 = bch2_btree_iter_peek_slot(&iter2);
+			k2 = bch2_bkey_get_iter(trans, &iter2, id, whiteout_pos,
+						BTREE_ITER_NOT_EXTENTS|
+						BTREE_ITER_INTENT);
 			ret = bkey_err(k2);
 
 			if (!ret && k2.k->type == KEY_TYPE_deleted) {
diff --git a/fs/bcachefs/ec.c b/fs/bcachefs/ec.c
index cf9f8c026034..439fa540323f 100644
--- a/fs/bcachefs/ec.c
+++ b/fs/bcachefs/ec.c
@@ -452,9 +452,8 @@ static int get_stripe_key_trans(struct btree_trans *trans, u64 idx,
 	struct bkey_s_c k;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_stripes,
-			     POS(0, idx), BTREE_ITER_SLOTS);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_stripes,
+			       POS(0, idx), BTREE_ITER_SLOTS);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
@@ -755,9 +754,8 @@ static int ec_stripe_delete(struct btree_trans *trans, u64 idx)
 	struct bkey_s_c_stripe s;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_stripes, POS(0, idx),
-			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_stripes, POS(0, idx),
+			       BTREE_ITER_INTENT);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
@@ -835,9 +833,8 @@ static int ec_stripe_key_update(struct btree_trans *trans,
 	struct bkey_s_c k;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_stripes,
-			     new->k.p, BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_stripes,
+			       new->k.p, BTREE_ITER_INTENT);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
diff --git a/fs/bcachefs/fsck.c b/fs/bcachefs/fsck.c
index eda1f030f784..142e64922d8f 100644
--- a/fs/bcachefs/fsck.c
+++ b/fs/bcachefs/fsck.c
@@ -72,26 +72,14 @@ static s64 bch2_count_subdirs(struct btree_trans *trans, u64 inum,
 static int __snapshot_lookup_subvol(struct btree_trans *trans, u32 snapshot,
 				    u32 *subvol)
 {
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots,
-			     POS(0, snapshot), 0);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
-	if (ret)
-		goto err;
-
-	if (k.k->type != KEY_TYPE_snapshot) {
+	struct bch_snapshot s;
+	int ret = bch2_bkey_get_val_typed(trans, BTREE_ID_snapshots,
+					  POS(0, snapshot), 0,
+					  snapshot, &s);
+	if (!ret)
+		*subvol = le32_to_cpu(s.subvol);
+	else if (ret == -ENOENT)
 		bch_err(trans->c, "snapshot %u not fonud", snapshot);
-		ret = -ENOENT;
-		goto err;
-	}
-
-	*subvol = le32_to_cpu(bkey_s_c_to_snapshot(k).v->subvol);
-err:
-	bch2_trans_iter_exit(trans, &iter);
 	return ret;
 
 }
@@ -152,9 +140,8 @@ static int __lookup_inode(struct btree_trans *trans, u64 inode_nr,
 	struct bkey_s_c k;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_inodes,
-			     SPOS(0, inode_nr, *snapshot), 0);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_inodes,
+			       SPOS(0, inode_nr, *snapshot), 0);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
@@ -259,10 +246,8 @@ static int fsck_inode_rm(struct btree_trans *trans, u64 inum, u32 snapshot)
 retry:
 	bch2_trans_begin(trans);
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_inodes,
-			     SPOS(0, inum, snapshot), BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_inodes,
+			       SPOS(0, inum, snapshot), BTREE_ITER_INTENT);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
@@ -453,22 +438,14 @@ static int remove_backpointer(struct btree_trans *trans,
 			      struct bch_inode_unpacked *inode)
 {
 	struct btree_iter iter;
-	struct bkey_s_c k;
+	struct bkey_s_c_dirent d;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_dirents,
-			     POS(inode->bi_dir, inode->bi_dir_offset), 0);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
-	if (ret)
-		goto out;
-	if (k.k->type != KEY_TYPE_dirent) {
-		ret = -ENOENT;
-		goto out;
-	}
-
-	ret = __remove_dirent(trans, k.k->p);
-out:
+	d = bch2_bkey_get_iter_typed(trans, &iter, BTREE_ID_dirents,
+				     POS(inode->bi_dir, inode->bi_dir_offset), 0,
+				     dirent);
+	ret =   bkey_err(d) ?:
+		__remove_dirent(trans, d.k->p);
 	bch2_trans_iter_exit(trans, &iter);
 	return ret;
 }
@@ -1081,20 +1058,7 @@ static struct bkey_s_c_dirent dirent_get_by_pos(struct btree_trans *trans,
 						struct btree_iter *iter,
 						struct bpos pos)
 {
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_iter_init(trans, iter, BTREE_ID_dirents, pos, 0);
-	k = bch2_btree_iter_peek_slot(iter);
-	ret = bkey_err(k);
-	if (!ret && k.k->type != KEY_TYPE_dirent)
-		ret = -ENOENT;
-	if (ret) {
-		bch2_trans_iter_exit(trans, iter);
-		return (struct bkey_s_c_dirent) { .k = ERR_PTR(ret) };
-	}
-
-	return bkey_s_c_to_dirent(k);
+	return bch2_bkey_get_iter_typed(trans, iter, BTREE_ID_dirents, pos, 0, dirent);
 }
 
 static bool inode_points_to_dirent(struct bch_inode_unpacked *inode,
diff --git a/fs/bcachefs/inode.c b/fs/bcachefs/inode.c
index 107210dd9c9a..ddcd7b125f32 100644
--- a/fs/bcachefs/inode.c
+++ b/fs/bcachefs/inode.c
@@ -329,13 +329,12 @@ int bch2_inode_peek(struct btree_trans *trans,
 	if (ret)
 		return ret;
 
-	bch2_trans_iter_init(trans, iter, BTREE_ID_inodes,
-			     SPOS(0, inum.inum, snapshot),
-			     flags|BTREE_ITER_CACHED);
-	k = bch2_btree_iter_peek_slot(iter);
+	k = bch2_bkey_get_iter(trans, iter, BTREE_ID_inodes,
+			       SPOS(0, inum.inum, snapshot),
+			       flags|BTREE_ITER_CACHED);
 	ret = bkey_err(k);
 	if (ret)
-		goto err;
+		return ret;
 
 	ret = bkey_is_inode(k.k) ? 0 : -ENOENT;
 	if (ret)
@@ -760,11 +759,9 @@ retry:
 	if (ret)
 		goto err;
 
-	bch2_trans_iter_init(&trans, &iter, BTREE_ID_inodes,
-			     SPOS(0, inum.inum, snapshot),
-			     BTREE_ITER_INTENT|BTREE_ITER_CACHED);
-	k = bch2_btree_iter_peek_slot(&iter);
-
+	k = bch2_bkey_get_iter(&trans, &iter, BTREE_ID_inodes,
+			       SPOS(0, inum.inum, snapshot),
+			       BTREE_ITER_INTENT|BTREE_ITER_CACHED);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
diff --git a/fs/bcachefs/io.c b/fs/bcachefs/io.c
index 110a92f38e86..1ae58d970c1b 100644
--- a/fs/bcachefs/io.c
+++ b/fs/bcachefs/io.c
@@ -2312,9 +2312,8 @@ static int __bch2_rbio_narrow_crcs(struct btree_trans *trans,
 	if (crc_is_compressed(rbio->pick.crc))
 		return 0;
 
-	bch2_trans_iter_init(trans, &iter, rbio->data_btree, rbio->data_pos,
-			     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, rbio->data_btree, rbio->data_pos,
+			       BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 	if ((ret = bkey_err(k)))
 		goto out;
 
@@ -2550,10 +2549,8 @@ int __bch2_read_indirect_extent(struct btree_trans *trans,
 	reflink_offset = le64_to_cpu(bkey_i_to_reflink_p(orig_k->k)->v.idx) +
 		*offset_into_extent;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_reflink,
-			     POS(0, reflink_offset),
-			     BTREE_ITER_SLOTS);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_reflink,
+			       POS(0, reflink_offset), 0);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
diff --git a/fs/bcachefs/lru.c b/fs/bcachefs/lru.c
index 0e6193d6b5f8..4f23e88f6ae1 100644
--- a/fs/bcachefs/lru.c
+++ b/fs/bcachefs/lru.c
@@ -114,8 +114,7 @@ static int bch2_check_lru_key(struct btree_trans *trans,
 			alloc_pos.inode, alloc_pos.offset))
 		return bch2_btree_delete_at(trans, lru_iter, 0);
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc, alloc_pos, 0);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_alloc, alloc_pos, 0);
 	ret = bkey_err(k);
 	if (ret)
 		goto err;
diff --git a/fs/bcachefs/movinggc.c b/fs/bcachefs/movinggc.c
index bd5d5221788a..0d96346d5040 100644
--- a/fs/bcachefs/movinggc.c
+++ b/fs/bcachefs/movinggc.c
@@ -91,12 +91,9 @@ static int bch2_bucket_is_movable(struct btree_trans *trans,
 				b->k.bucket.offset))
 		return 0;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
-			     b->k.bucket, BTREE_ITER_CACHED);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_alloc,
+			       b->k.bucket, BTREE_ITER_CACHED);
 	ret = bkey_err(k);
-	bch2_trans_iter_exit(trans, &iter);
-
 	if (ret)
 		return ret;
 
@@ -108,14 +105,7 @@ static int bch2_bucket_is_movable(struct btree_trans *trans,
 		a->fragmentation_lru &&
 		a->fragmentation_lru <= time;
 
-	if (!ret) {
-		struct printbuf buf = PRINTBUF;
-
-		bch2_bkey_val_to_text(&buf, trans->c, k);
-		pr_debug("%s", buf.buf);
-		printbuf_exit(&buf);
-	}
-
+	bch2_trans_iter_exit(trans, &iter);
 	return ret;
 }
 
diff --git a/fs/bcachefs/quota.c b/fs/bcachefs/quota.c
index 22cd662429d3..7734e0dfe523 100644
--- a/fs/bcachefs/quota.c
+++ b/fs/bcachefs/quota.c
@@ -901,10 +901,8 @@ static int bch2_set_quota_trans(struct btree_trans *trans,
 	struct bkey_s_c k;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_quotas, new_quota->k.p,
-			     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_quotas, new_quota->k.p,
+			       BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 	ret = bkey_err(k);
 	if (unlikely(ret))
 		return ret;
diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
index 91a66b5916eb..6214691fa441 100644
--- a/fs/bcachefs/recovery.c
+++ b/fs/bcachefs/recovery.c
@@ -1065,12 +1065,11 @@ static int bch2_fs_upgrade_for_subvolumes(struct btree_trans *trans)
 	struct bch_inode_unpacked inode;
 	int ret;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_inodes,
-			     SPOS(0, BCACHEFS_ROOT_INO, U32_MAX), 0);
-	k = bch2_btree_iter_peek_slot(&iter);
+	k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_inodes,
+			       SPOS(0, BCACHEFS_ROOT_INO, U32_MAX), 0);
 	ret = bkey_err(k);
 	if (ret)
-		goto err;
+		return ret;
 
 	if (!bkey_is_inode(k.k)) {
 		bch_err(trans->c, "root inode not found");
diff --git a/fs/bcachefs/subvolume.c b/fs/bcachefs/subvolume.c
index 31af41df09e3..376444860ac2 100644
--- a/fs/bcachefs/subvolume.c
+++ b/fs/bcachefs/subvolume.c
@@ -103,20 +103,8 @@ int bch2_mark_snapshot(struct btree_trans *trans,
 static int snapshot_lookup(struct btree_trans *trans, u32 id,
 			   struct bch_snapshot *s)
 {
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots, POS(0, id),
-			     BTREE_ITER_WITH_UPDATES);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k) ?: k.k->type == KEY_TYPE_snapshot ? 0 : -ENOENT;
-
-	if (!ret)
-		*s = *bkey_s_c_to_snapshot(k).v;
-
-	bch2_trans_iter_exit(trans, &iter);
-	return ret;
+	return bch2_bkey_get_val_typed(trans, BTREE_ID_snapshots, POS(0, id),
+				       BTREE_ITER_WITH_UPDATES, snapshot, s);
 }
 
 static int snapshot_live(struct btree_trans *trans, u32 id)
@@ -402,27 +390,20 @@ err:
 
 static int bch2_snapshot_node_delete(struct btree_trans *trans, u32 id)
 {
+	struct bch_fs *c = trans->c;
 	struct btree_iter iter, p_iter = (struct btree_iter) { NULL };
-	struct bkey_s_c k;
 	struct bkey_s_c_snapshot s;
 	u32 parent_id;
 	unsigned i;
 	int ret = 0;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots, POS(0, id),
-			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
-	if (ret)
-		goto err;
+	s = bch2_bkey_get_iter_typed(trans, &iter, BTREE_ID_snapshots, POS(0, id),
+				     BTREE_ITER_INTENT, snapshot);
+	ret = bkey_err(s);
+	bch2_fs_inconsistent_on(ret == -ENOENT, c, "missing snapshot %u", id);
 
-	if (k.k->type != KEY_TYPE_snapshot) {
-		bch2_fs_inconsistent(trans->c, "missing snapshot %u", id);
-		ret = -ENOENT;
+	if (ret)
 		goto err;
-	}
-
-	s = bkey_s_c_to_snapshot(k);
 
 	BUG_ON(!BCH_SNAPSHOT_DELETED(s.v));
 	parent_id = le32_to_cpu(s.v->parent);
@@ -436,7 +417,7 @@ static int bch2_snapshot_node_delete(struct btree_trans *trans, u32 id)
 		parent = bch2_bkey_get_mut_typed(trans, &p_iter, snapshot);
 		ret = PTR_ERR_OR_ZERO(parent);
 		if (unlikely(ret)) {
-			bch2_fs_inconsistent_on(ret == -ENOENT, trans->c, "missing snapshot %u", parent_id);
+			bch2_fs_inconsistent_on(ret == -ENOENT, c, "missing snapshot %u", parent_id);
 			goto err;
 		}
 
@@ -445,7 +426,7 @@ static int bch2_snapshot_node_delete(struct btree_trans *trans, u32 id)
 				break;
 
 		if (i == 2)
-			bch_err(trans->c, "snapshot %u missing child pointer to %u",
+			bch_err(c, "snapshot %u missing child pointer to %u",
 				parent_id, id);
 		else
 			parent->v.children[i] = 0;
@@ -756,21 +737,10 @@ bch2_subvolume_get_inlined(struct btree_trans *trans, unsigned subvol,
 			   int iter_flags,
 			   struct bch_subvolume *s)
 {
-	struct btree_iter iter;
-	struct bkey_s_c k;
-	int ret;
-
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_subvolumes, POS(0, subvol),
-			     iter_flags);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k) ?: k.k->type == KEY_TYPE_subvolume ? 0 : -ENOENT;
-
-	if (ret == -ENOENT && inconsistent_if_not_found)
-		bch2_fs_inconsistent(trans->c, "missing subvolume %u", subvol);
-	if (!ret)
-		*s = *bkey_s_c_to_subvolume(k).v;
-
-	bch2_trans_iter_exit(trans, &iter);
+	int ret = bch2_bkey_get_val_typed(trans, BTREE_ID_subvolumes, POS(0, subvol),
+					  iter_flags, subvolume, s);
+	bch2_fs_inconsistent_on(ret == -ENOENT && inconsistent_if_not_found,
+				trans->c, "missing subvolume %u", subvol);
 	return ret;
 }
 
@@ -813,28 +783,20 @@ int bch2_subvolume_get_snapshot(struct btree_trans *trans, u32 subvol,
 int bch2_subvolume_delete(struct btree_trans *trans, u32 subvolid)
 {
 	struct btree_iter iter;
-	struct bkey_s_c k;
 	struct bkey_s_c_subvolume subvol;
 	struct btree_trans_commit_hook *h;
 	u32 snapid;
 	int ret = 0;
 
-	bch2_trans_iter_init(trans, &iter, BTREE_ID_subvolumes,
-			     POS(0, subvolid),
-			     BTREE_ITER_CACHED|
-			     BTREE_ITER_INTENT);
-	k = bch2_btree_iter_peek_slot(&iter);
-	ret = bkey_err(k);
+	subvol = bch2_bkey_get_iter_typed(trans, &iter,
+				BTREE_ID_subvolumes, POS(0, subvolid),
+				BTREE_ITER_CACHED|BTREE_ITER_INTENT,
+				subvolume);
+	ret = bkey_err(subvol);
+	bch2_fs_inconsistent_on(ret == -ENOENT, trans->c, "missing subvolume %u", subvolid);
 	if (ret)
-		goto err;
-
-	if (k.k->type != KEY_TYPE_subvolume) {
-		bch2_fs_inconsistent(trans->c, "missing subvolume %u", subvolid);
-		ret = -EIO;
-		goto err;
-	}
+		return ret;
 
-	subvol = bkey_s_c_to_subvolume(k);
 	snapid = le32_to_cpu(subvol.v->snapshot);
 
 	ret = bch2_btree_delete_at(trans, &iter, 0);