I/O Error Test 3 ================ commit "bcache: fix inaccurate io state for detached bcache devices" Probçem: on detached bcache devices, iostat reports non-zero 'avgqu-sz' and '%util' even after IO stopped. Original kernel: iostat fields are non-zero on I/O idle. Modified kernel: iostat fields are all zero on I/O idle. Original -------- # uname -rv 4.15.0-55-generic #60-Ubuntu SMP Tue Jul 2 18:22:20 UTC 2019 # ./setup.sh >/dev/null 2>&1 [ 118.371172] bcache: register_bdev() registered backing device dm-0 [ 118.377221] bcache: run_cache_set() invalidating existing data [ 118.386614] bcache: register_cache() registered cache device dm-1 [ 120.373682] bcache: bch_cached_dev_attach() Caching dm-0 as bcache0 on set 4f2b6518-1a58-42e0-8720-42b535cb826f # lsblk -e 252 NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT loop0 7:0 0 1G 0 loop └─fake-loop0 253:0 0 1024M 0 dm └─bcache0 251:0 0 1024M 0 disk loop1 7:1 0 1G 0 loop └─fake-loop1 253:1 0 1024M 0 dm └─bcache0 251:0 0 1024M 0 disk # echo 1 > /sys/block/bcache0/bcache/detach [ 131.847360] bcache: cached_dev_detach_finish() Caching disabled for dm-0 # lsblk -e 252 NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT loop0 7:0 0 1G 0 loop └─fake-loop0 253:0 0 1024M 0 dm └─bcache0 251:0 0 1024M 0 disk loop1 7:1 0 1G 0 loop └─fake-loop1 253:1 0 1024M 0 dm # dd if=/dev/zero of=/dev/bcache0 bs=4k dd: error writing '/dev/bcache0': No space left on device 262142+0 records in 262141+0 records out 1073729536 bytes (1.1 GB, 1.0 GiB) copied, 3.86316 s, 278 MB/s # sync # iostat -xy 1 10 /dev/bcache0 | grep bcache0 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 262224.00 0.00 0.00 0.00 100.00 Modified -------- # uname -rv 4.15.0-55-generic #60+test20190703build1bcache1-Ubuntu SMP Wed Jul 3 21:41:37 UTC # ./setup.sh >/dev/null 2>&1 [ 26.923296] bcache: register_bdev() registered backing device dm-0 [ 26.928998] bcache: run_cache_set() invalidating existing data [ 26.940144] bcache: register_cache() registered cache device dm-1 [ 28.920772] bcache: bch_cached_dev_attach() Caching dm-0 as bcache0 on set bf256397-22a4-40ac-8ff3-0026fd28354c # lsblk -e 252 NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT loop0 7:0 0 1G 0 loop └─fake-loop0 253:0 0 1024M 0 dm └─bcache0 251:0 0 1024M 0 disk loop1 7:1 0 1G 0 loop └─fake-loop1 253:1 0 1024M 0 dm └─bcache0 251:0 0 1024M 0 disk # echo 1 > /sys/block/bcache0/bcache/detach [ 42.292538] bcache: cached_dev_detach_finish() Caching disabled for dm-0 # lsblk -e 252 NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT loop0 7:0 0 1G 0 loop └─fake-loop0 253:0 0 1024M 0 dm └─bcache0 251:0 0 1024M 0 disk loop1 7:1 0 1G 0 loop └─fake-loop1 253:1 0 1024M 0 dm # dd if=/dev/zero of=/dev/bcache0 bs=4k dd: error writing '/dev/bcache0': No space left on device 262142+0 records in 262141+0 records out 1073729536 bytes (1.1 GB, 1.0 GiB) copied, 3.86123 s, 278 MB/s # sync # iostat -xy 1 10 /dev/bcache0 | grep bcache0 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 bcache0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00