bcachefs: don't block reads if we're promoting

The promote path calls data_update_init() and now that we take locks here,
there's potential for promote to block our read path, just error
when we can't take the lock instead of blocking.

Signed-off-by: Daniel Hill <daniel@gluo.nz>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/bcachefs/io.c b/fs/bcachefs/io.c
index 1436863fe418..6f7e4dac4268 100644
--- a/fs/bcachefs/io.c
+++ b/fs/bcachefs/io.c
@@ -2023,6 +2023,13 @@ static struct promote_op *__promote_alloc(struct btree_trans *trans,
 				.write_flags	= BCH_WRITE_ALLOC_NOWAIT|BCH_WRITE_CACHED,
 			},
 			btree_id, k);
+	if (ret == -BCH_ERR_nocow_lock_blocked) {
+		ret = rhashtable_remove_fast(&c->promote_table, &op->hash,
+					bch_promote_params);
+		BUG_ON(ret);
+		goto err;
+	}
+
 	BUG_ON(ret);
 	op->write.op.end_io = promote_done;