Hello, I'm using bcache on a very basic setup: no MD or LVM involved. /dev/sda4 (900Mo) is the backing device while /dev/sdb (120G) is the cache device. On top of bcache0 I'm using ext4 and I'm using it as my root device. I initially created the bcache0 device with default using writethough mode. I haven't (yet) experienced any issues using this mode: I successfully installed my system (archlinux) on it. I decided to switch to writeback mode and encounter several times the same issue: after doing a lot of IOs (for example when installing new packages) one process is stuck in D state. Currently I can see this: # ps aux | grep D+ root 1080 0.0 0.0 41796 5728 pts/0 D+ 12:59 0:00 gtk-update-icon # cat /proc/1080/stack [<ffffffff8113270e>] sleep_on_page+0xe/0x20 [<ffffffff811324bf>] wait_on_page_bit+0x7f/0x90 [<ffffffff8113264b>] filemap_fdatawait_range+0x11b/0x1a0 [<ffffffff81133d3f>] filemap_write_and_wait_range+0x3f/0x70 [<ffffffffa02ad4da>] ext4_sync_file+0xba/0x390 [ext4] [<ffffffff811cde56>] do_fsync+0x56/0x80 [<ffffffff811ce0e0>] SyS_fsync+0x10/0x20 [<ffffffff814ea5dd>] system_call_fastpath+0x1a/0x1f [<ffffffffffffffff>] 0xffffffffffffffff >From that point I'm not really sure what I should do to restore the system without loosing or breaking badly my rootfs. Any advices are welcome. Please find below some additionnal information that might help to fix this issue: # mount | grep bcache /dev/bcache0 on / type ext4 (rw,relatime,data=ordered) # uname -r 3.11.6-1-ARCH # bcache-super-show /dev/sda4 sb.magic ok sb.first_sector 8 [match] sb.csum F828E134D5AB890C [match] sb.version 1 [backing device] dev.label (empty) dev.uuid 62839366-e5a9-43a9-9984-fc8f2aefe9de dev.sectors_per_block 1 dev.sectors_per_bucket 1024 dev.data.first_sector 16 dev.data.cache_mode 1 [writeback] dev.data.cache_state 2 [dirty] cset.uuid 50485be4-15f7-424f-a01b-4c65fdf8487d # bcache-super-show /dev/sdb sb.magic ok sb.first_sector 8 [match] sb.csum 692BB25984E31571 [match] sb.version 3 [cache device] dev.label (empty) dev.uuid a63ec68a-6a71-497e-86db-0dd71bbfb404 dev.sectors_per_block 1 dev.sectors_per_bucket 1024 dev.cache.first_sector 1024 dev.cache.cache_sectors 234439680 dev.cache.total_sectors 234440704 dev.cache.ordered yes dev.cache.discard yes dev.cache.pos 0 dev.cache.replacement 0 [lru] cset.uuid 50485be4-15f7-424f-a01b-4c65fdf8487d I attached dmesg output which has been generated after doing "echo t >/proc/sysrq-trigger" Thanks -- Francis
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