Host operating system: output of uname -a

Linux sarbian 5.13.5-arch1-1 #1 SMP PREEMPT Sun, 25 Jul 2021 18:02:58 +0000 x86_64 GNU/Linux

node_exporter version: output of node_exporter --version

node_exporter, version 1.2.0 (branch: tarball, revision: 1.2.0)
build user: someone@builder
build date:
go version: go1.16.5
platform: linux/amd64

node_exporter command line flags

--collector.systemd --collector.perf --collector.interrupts --no-collector.rapl --collector.bcache --collector.bcache.priorityStats --collector.textfile.directory=/var/lib/prometheus/node-exporter

Are you running node_exporter in Docker?

No

What did you do that produced an error?

Updated to kernel 5.13 from 5.11

What did you expect to see?

Metrics starting with node_bcache like node_bcache_cache_hits_total

What did you see instead?

No bcache metrics at all
$ curl -s 192.168.1.3:9100/metrics | grep node_bcache | wc -l
0

Errors filling the service log:
Jul 28 20:48:27 sarbian prometheus-node-exporter[2198407]: level=error ts=2021-07-28T18:48:27.138Z caller=collector.go:169 msg="collector failed" name=bcache duration_seconds=0.004825363 err="failed to retrieve bcache stats: failed to read: /sys/fs/bcache/13838fb3-547e-404f-bbd1-d4da4aec10ae/stats_five_minute/cache_readaheads"

$ ls -l
ls -l /sys/fs/bcache/13838fb3-547e-404f-bbd1-d4da4aec10ae/stats_five_minute
total 0
-r--r--r-- 1 root root 4096 Jul 26 18:10 bypassed
-r--r--r-- 1 root root 4096 Jul 26 18:10 cache_bypass_hits
-r--r--r-- 1 root root 4096 Jul 26 18:10 cache_bypass_misses
-r--r--r-- 1 root root 4096 Jul 28 20:47 cache_hit_ratio
-r--r--r-- 1 root root 4096 Jul 26 18:10 cache_hits
-r--r--r-- 1 root root 4096 Jul 26 18:10 cache_miss_collisions
-r--r--r-- 1 root root 4096 Jul 26 18:10 cache_misses

cache_readaheads was removed in Linux kernel 5.13:
https://lkml.org/lkml/2021/5/31/1602