bcache TRIM support buggy - mkfs.ext4 error discarding blocks

Bug #1810276 reported by Robert Collins on 2019-01-02

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linux (Ubuntu)
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Bug Description

Sorry that this is a little vague, I ran into it and didn't run it down to ground; this was on the cosmic daily server installer build.

hardware: 4 HDD;s, 1 NVMe SSD.

configuration: 1x 512MB ESP per drive, then for the HDDs the second partition for an mdraid raid5 set.
layered on that, bcache with the SSD as cache, and md0 as backing
layered on that, lvm with one big vg and a lv for root
mkfs.ext4 on that lv would break, as a TRIM command it issued would error in bcache.

The cache was constructed like so: make-bcache -o 7741440 -w 2k -B /dev/md127 -C /dev/nvme0n1p2

I'm not familiar enough with TRIM/discard to know whether commands /layers are meant to not issue them unless supported, or whether they should be issued and discarded; either way something breaks here - bcache may be incorrectly advertising that bcache0 supports trim, or lvm may be checking in the wrong way, or mkfs.ext4 etc etc.

Though I can rule mkfs.ext4 out - lvremove also issues a discard and fails in the same way.

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1810276

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

Changed in linux (Ubuntu):
status: New → Incomplete
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