diff --git a/fs/bcachefs/alloc_background.c b/fs/bcachefs/alloc_background.c
index 645b5ed4babb..4e4a448f6931 100644
--- a/fs/bcachefs/alloc_background.c
+++ b/fs/bcachefs/alloc_background.c
@@ -332,7 +332,6 @@ void bch2_alloc_v4_swab(struct bkey_s k)
 	a->io_time[1]		= swab64(a->io_time[1]);
 	a->stripe		= swab32(a->stripe);
 	a->nr_external_backpointers = swab32(a->nr_external_backpointers);
-	a->fragmentation_lru	= swab64(a->fragmentation_lru);
 	a->stripe_sectors	= swab32(a->stripe_sectors);
 
 	bps = alloc_v4_backpointers(a);
@@ -347,6 +346,7 @@ void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c
 {
 	struct bch_alloc_v4 _a;
 	const struct bch_alloc_v4 *a = bch2_alloc_to_v4(k, &_a);
+	struct bch_dev *ca = c ? bch2_dev_bucket_tryget_noerror(c, k.k->p) : NULL;
 
 	prt_newline(out);
 	printbuf_indent_add(out, 2);
@@ -364,9 +364,13 @@ void bch2_alloc_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c
 	prt_printf(out, "stripe_redundancy %u\n",	a->stripe_redundancy);
 	prt_printf(out, "io_time[READ]     %llu\n",	a->io_time[READ]);
 	prt_printf(out, "io_time[WRITE]    %llu\n",	a->io_time[WRITE]);
-	prt_printf(out, "fragmentation     %llu\n",	a->fragmentation_lru);
+
+	if (ca)
+		prt_printf(out, "fragmentation     %llu\n",	alloc_lru_idx_fragmentation(*a, ca));
 	prt_printf(out, "bp_start          %llu\n", BCH_ALLOC_V4_BACKPOINTERS_START(a));
 	printbuf_indent_sub(out, 2);
+
+	bch2_dev_put(ca);
 }
 
 void __bch2_alloc_to_v4(struct bkey_s_c k, struct bch_alloc_v4 *out)
@@ -882,12 +886,13 @@ int bch2_trigger_alloc(struct btree_trans *trans,
 				goto err;
 		}
 
-		new_a->fragmentation_lru = alloc_lru_idx_fragmentation(*new_a, ca);
-		if (old_a->fragmentation_lru != new_a->fragmentation_lru) {
+		old_lru = alloc_lru_idx_fragmentation(*old_a, ca);
+		new_lru = alloc_lru_idx_fragmentation(*new_a, ca);
+		if (old_lru != new_lru) {
 			ret = bch2_lru_change(trans,
 					BCH_LRU_FRAGMENTATION_START,
 					bucket_to_u64(new.k->p),
-					old_a->fragmentation_lru, new_a->fragmentation_lru);
+					old_lru, new_lru);
 			if (ret)
 				goto err;
 		}
@@ -1629,18 +1634,22 @@ static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
 	if (ret)
 		return ret;
 
+	struct bch_dev *ca = bch2_dev_tryget_noerror(c, alloc_k.k->p.inode);
+	if (!ca)
+		return 0;
+
 	a = bch2_alloc_to_v4(alloc_k, &a_convert);
 
-	if (a->fragmentation_lru) {
+	u64 lru_idx = alloc_lru_idx_fragmentation(*a, ca);
+	if (lru_idx) {
 		ret = bch2_lru_check_set(trans, BCH_LRU_FRAGMENTATION_START,
-					 a->fragmentation_lru,
-					 alloc_k, last_flushed);
+					 lru_idx, alloc_k, last_flushed);
 		if (ret)
-			return ret;
+			goto err;
 	}
 
 	if (a->data_type != BCH_DATA_cached)
-		return 0;
+		goto err;
 
 	if (fsck_err_on(!a->io_time[READ],
 			trans, alloc_key_cached_but_read_time_zero,
@@ -1669,6 +1678,7 @@ static int bch2_check_alloc_to_lru_ref(struct btree_trans *trans,
 		goto err;
 err:
 fsck_err:
+	bch2_dev_put(ca);
 	printbuf_exit(&buf);
 	return ret;
 }
diff --git a/fs/bcachefs/alloc_background_format.h b/fs/bcachefs/alloc_background_format.h
index f754a2951d8a..befdaa95c515 100644
--- a/fs/bcachefs/alloc_background_format.h
+++ b/fs/bcachefs/alloc_background_format.h
@@ -70,7 +70,7 @@ struct bch_alloc_v4 {
 	__u32			stripe;
 	__u32			nr_external_backpointers;
 	/* end of fields in original version of alloc_v4 */
-	__u64			fragmentation_lru;
+	__u64			_fragmentation_lru; /* obsolete */
 	__u32			stripe_sectors;
 	__u32			pad;
 } __packed __aligned(8);
diff --git a/fs/bcachefs/btree_gc.c b/fs/bcachefs/btree_gc.c
index 660d2fa02da2..771154e3a291 100644
--- a/fs/bcachefs/btree_gc.c
+++ b/fs/bcachefs/btree_gc.c
@@ -828,8 +828,6 @@ static int bch2_alloc_write_key(struct btree_trans *trans,
 			return ret;
 	}
 
-	gc.fragmentation_lru = alloc_lru_idx_fragmentation(gc, ca);
-
 	if (fsck_err_on(new.data_type != gc.data_type,
 			trans, alloc_key_data_type_wrong,
 			"bucket %llu:%llu gen %u has wrong data_type"
@@ -857,7 +855,6 @@ static int bch2_alloc_write_key(struct btree_trans *trans,
 	copy_bucket_field(alloc_key_cached_sectors_wrong,	cached_sectors);
 	copy_bucket_field(alloc_key_stripe_wrong,		stripe);
 	copy_bucket_field(alloc_key_stripe_redundancy_wrong,	stripe_redundancy);
-	copy_bucket_field(alloc_key_fragmentation_lru_wrong,	fragmentation_lru);
 #undef copy_bucket_field
 
 	if (!bch2_alloc_v4_cmp(*old, new))
diff --git a/fs/bcachefs/lru.c b/fs/bcachefs/lru.c
index dd5df668131a..10857eccdeaf 100644
--- a/fs/bcachefs/lru.c
+++ b/fs/bcachefs/lru.c
@@ -133,7 +133,9 @@ static int bch2_check_lru_key(struct btree_trans *trans,
 	u64 idx;
 	int ret;
 
-	if (fsck_err_on(!bch2_dev_bucket_exists(c, alloc_pos),
+	struct bch_dev *ca = bch2_dev_bucket_tryget_noerror(c, alloc_pos);
+
+	if (fsck_err_on(!ca,
 			trans, lru_entry_to_invalid_bucket,
 			"lru key points to nonexistent device:bucket %llu:%llu",
 			alloc_pos.inode, alloc_pos.offset))
@@ -151,7 +153,7 @@ static int bch2_check_lru_key(struct btree_trans *trans,
 		idx = alloc_lru_idx_read(*a);
 		break;
 	case BCH_LRU_fragmentation:
-		idx = a->fragmentation_lru;
+		idx = alloc_lru_idx_fragmentation(*a, ca);
 		break;
 	}
 
@@ -174,6 +176,7 @@ static int bch2_check_lru_key(struct btree_trans *trans,
 err:
 fsck_err:
 	bch2_trans_iter_exit(trans, &iter);
+	bch2_dev_put(ca);
 	printbuf_exit(&buf2);
 	printbuf_exit(&buf1);
 	return ret;
diff --git a/fs/bcachefs/move.c b/fs/bcachefs/move.c
index 7d3920e03742..8c456d8b8b99 100644
--- a/fs/bcachefs/move.c
+++ b/fs/bcachefs/move.c
@@ -692,7 +692,7 @@ int bch2_evacuate_bucket(struct moving_context *ctxt,
 	a = bch2_alloc_to_v4(k, &a_convert);
 	dirty_sectors = bch2_bucket_sectors_dirty(*a);
 	bucket_size = ca->mi.bucket_size;
-	fragmentation = a->fragmentation_lru;
+	fragmentation = alloc_lru_idx_fragmentation(*a, ca);
 
 	ret = bch2_btree_write_buffer_tryflush(trans);
 	bch_err_msg(c, ret, "flushing btree write buffer");
diff --git a/fs/bcachefs/movinggc.c b/fs/bcachefs/movinggc.c
index d86565bf07c8..d658be90f737 100644
--- a/fs/bcachefs/movinggc.c
+++ b/fs/bcachefs/movinggc.c
@@ -73,6 +73,7 @@ move_bucket_in_flight_add(struct buckets_in_flight *list, struct move_bucket b)
 static int bch2_bucket_is_movable(struct btree_trans *trans,
 				  struct move_bucket *b, u64 time)
 {
+	struct bch_fs *c = trans->c;
 	struct btree_iter iter;
 	struct bkey_s_c k;
 	struct bch_alloc_v4 _a;
@@ -90,14 +91,19 @@ static int bch2_bucket_is_movable(struct btree_trans *trans,
 	if (ret)
 		return ret;
 
+	struct bch_dev *ca = bch2_dev_tryget(c, k.k->p.inode);
+	if (!ca)
+		goto out;
+
 	a = bch2_alloc_to_v4(k, &_a);
 	b->k.gen	= a->gen;
 	b->sectors	= bch2_bucket_sectors_dirty(*a);
+	u64 lru_idx	= alloc_lru_idx_fragmentation(*a, ca);
 
-	ret = data_type_movable(a->data_type) &&
-		a->fragmentation_lru &&
-		a->fragmentation_lru <= time;
+	ret = lru_idx && lru_idx <= time;
 
+	bch2_dev_put(ca);
+out:
 	bch2_trans_iter_exit(trans, &iter);
 	return ret;
 }
diff --git a/fs/bcachefs/sb-errors_format.h b/fs/bcachefs/sb-errors_format.h
index 6a63d24180ca..b4024870b65e 100644
--- a/fs/bcachefs/sb-errors_format.h
+++ b/fs/bcachefs/sb-errors_format.h
@@ -115,8 +115,8 @@ enum bch_fsck_flags {
 	x(alloc_key_data_type_inconsistency,			101,	0)		\
 	x(alloc_key_to_missing_dev_bucket,			102,	0)		\
 	x(alloc_key_cached_inconsistency,			103,	0)		\
-	x(alloc_key_cached_but_read_time_zero,			104,	0)		\
-	x(alloc_key_to_missing_lru_entry,			105,	0)		\
+	x(alloc_key_cached_but_read_time_zero,			104,	FSCK_AUTOFIX)	\
+	x(alloc_key_to_missing_lru_entry,			105,	FSCK_AUTOFIX)	\
 	x(alloc_key_data_type_wrong,				106,	FSCK_AUTOFIX)	\
 	x(alloc_key_gen_wrong,					107,	FSCK_AUTOFIX)	\
 	x(alloc_key_dirty_sectors_wrong,			108,	FSCK_AUTOFIX)	\