bcachefs: Make various async objs visible in debugfs

Add async objs list for
- promote_op
- bch_read_bio
- btree_read_bio
- btree_write_bio

This gets us introspection on in-flight async ops, and because under the
hood it uses fast_lists (percpu slot buffer on top of a radix tree),
it'll be fast enough to enable in production.

This will be very helpful for debugging "something got stuck" issues,
which have been cropping up from time to time (in the CI, especially
with folio writeback).

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

1 files changed, 26 insertions, 13 deletions

diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index df96e2c8ceda..abfd3a4c1d7d 100644
--- a/fs/bcachefs/io_read.c
+++ b/fs/bcachefs/io_read.c
@@ -9,6 +9,7 @@
 #include "bcachefs.h"
 #include "alloc_background.h"
 #include "alloc_foreground.h"
+#include "async_objs.h"
 #include "btree_update.h"
 #include "buckets.h"
 #include "checksum.h"
@@ -88,18 +89,6 @@ static bool bch2_target_congested(struct bch_fs *c, u16 target)
 
 /* Cache promotion on read */
 
-struct promote_op {
-	struct rcu_head		rcu;
-	u64			start_time;
-
-	struct rhash_head	hash;
-	struct bpos		pos;
-
-	struct work_struct	work;
-	struct data_update	write;
-	struct bio_vec		bi_inline_vecs[]; /* must be last */
-};
-
 static const struct rhashtable_params bch_promote_params = {
 	.head_offset		= offsetof(struct promote_op, hash),
 	.key_offset		= offsetof(struct promote_op, pos),
@@ -177,6 +166,8 @@ static noinline void promote_free(struct bch_read_bio *rbio)
 					 bch_promote_params);
 	BUG_ON(ret);
 
+	async_object_list_del(c, promote, op->list_idx);
+
 	bch2_data_update_exit(&op->write);
 
 	enumerated_ref_put(&c->writes, BCH_WRITE_REF_promote);
@@ -262,6 +253,10 @@ static struct bch_read_bio *__promote_alloc(struct btree_trans *trans,
 		goto err;
 	}
 
+	ret = async_object_list_add(c, promote, op, &op->list_idx);
+	if (ret < 0)
+		goto err_remove_hash;
+
 	ret = bch2_data_update_init(trans, NULL, NULL, &op->write,
 			writepoint_hashed((unsigned long) current),
 			&orig->opts,
@@ -273,7 +268,7 @@ static struct bch_read_bio *__promote_alloc(struct btree_trans *trans,
 	 * -BCH_ERR_ENOSPC_disk_reservation:
 	 */
 	if (ret)
-		goto err_remove_hash;
+		goto err_remove_list;
 
 	rbio_init_fragment(&op->write.rbio.bio, orig);
 	op->write.rbio.bounce	= true;
@@ -281,6 +276,8 @@ static struct bch_read_bio *__promote_alloc(struct btree_trans *trans,
 	op->write.op.end_io = promote_done;
 
 	return &op->write.rbio;
+err_remove_list:
+	async_object_list_del(c, promote, op->list_idx);
 err_remove_hash:
 	BUG_ON(rhashtable_remove_fast(&c->promote_table, &op->hash,
 				      bch_promote_params));
@@ -353,6 +350,18 @@ nopromote:
 	return NULL;
 }
 
+void bch2_promote_op_to_text(struct printbuf *out, struct promote_op *op)
+{
+	if (!op->write.read_done) {
+		prt_printf(out, "parent read: %px\n", op->write.rbio.parent);
+		printbuf_indent_add(out, 2);
+		bch2_read_bio_to_text(out, op->write.rbio.parent);
+		printbuf_indent_sub(out, 2);
+	}
+
+	bch2_data_update_to_text(out, &op->write);
+}
+
 /* Read */
 
 static int bch2_read_err_msg_trans(struct btree_trans *trans, struct printbuf *out,
@@ -421,6 +430,8 @@ static inline struct bch_read_bio *bch2_rbio_free(struct bch_read_bio *rbio)
 			else
 				promote_free(rbio);
 		} else {
+			async_object_list_del(rbio->c, rbio, rbio->list_idx);
+
 			if (rbio->bounce)
 				bch2_bio_free_pages_pool(rbio->c, &rbio->bio);
 
@@ -1246,6 +1257,8 @@ retry_pick:
 	rbio->bio.bi_iter.bi_sector = pick.ptr.offset;
 	rbio->bio.bi_end_io	= bch2_read_endio;
 
+	async_object_list_add(c, rbio, rbio, &rbio->list_idx);
+
 	if (rbio->bounce)
 		trace_and_count(c, io_read_bounce, &rbio->bio);