I'm using my own compilation of OpenWrt. I had no problems till latest release.
In newest version (18.06.1) I cannot get working lvm2:
# vgchange -ay
io_setup failed
Failed to create bcache io engine.
I'm not using bcache nor lvmcache.
Compiling 18.06.0 from same config.seed results in working lvm2
Target device x86-64 (apu2).
I tried to check dm-cache and bcache (CONFIG_BCACHE=y and CONFIG_DM_CACHE=y) in kernel_menuconfig but it didn't help.
I reverted lvm2 package to commit eebe024835d27f8457005ba30817703435a11f18.
It works.
Reported here
At first glance, it looks like CONFIG_AIO is required.
edit: On a second glance, version 177 is still used on 18.06.1.
Oh it gets better. CONFIG_AIO=y is specified in target/generic/config-
But when compiling, the kernel that is built has CONFIG_AIO undefined.
Anyway, I have a workaround. Doesn't get rid of the message though.
That’s possible that 18.06.1 uses 177.
I had problem with one package from revision specified in feeds.conf - I couldn't download it so I updated to feeds to latest revision.