Input/output error on newly created file

[Nikolaus Rath <Nikolaus@rath.org>]

Hello,

I just created an innocent 10 MB on a btrfs file system, yet my attempt
to read it a few seconds later (and ever since), just gives:

$ ls -l in-progress/mysterious-io-error 
-rw-rw-r-- 1 nikratio nikratio 10485760 May  8 14:41 in-progress/mysterious-io-error
$ cat in-progress/mysterious-io-error 
cat: in-progress/mysterious-io-error: Input/output error

I was hoping the kernel might tell me a little more about this, but:

$ dmesg | tail -3
[   48.982851] wlan0: RX AssocResp from 00:1f:33:be:9a:c4 (capab=0x411 status=0 aid=3)
[   48.983757] wlan0: associated
[ 2770.464505] kvm: zapping shadow pages for mmio generation wraparound


How can I find out the reason for the error? Is it a bug in BTRFS,
or somewhere else in the kernel ? Is my hardware broken?

Kernel is Debian's 4.5.0-0.bpo.1-amd64. This is a btrfs file system on a
LVM LV backed by a bcache array with two backing devices and one caching
device.


Best,
-Nikolaus

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