http://bugzilla.novell.com/show_bug.cgi?id=908706
--- Comment #15 from Neil Brown ---
Hi Mark,
thanks for all the details.
Part of the problem is that your /var/cache/fscache is in a 'btrfs' volume.
fscache doesn't work on btrfs. It requires the filesystem to provide a 'bmap'
interface user e.g. by the FIBMAP ioctl. btrfs doesn't provide that (for good
reason).
fscache (or more acturately: cachefiles which is the cache backend in use)
refuses to work if bmap isn't available, and this results in the
[ 859.668561] CacheFiles: Lookup failed error -1
[ 859.672224] CacheFiles: Lookup failed error -1
[ 859.675402] CacheFiles: Lookup failed error -1
[ 859.694269] CacheFiles: Lookup failed error -1
messages, and results in all the files always being empty.
The crash:
[ 859.700614] FS-Cache: Assertion failed
[ 859.700704] ------------[ cut here ]------------
[ 859.700765] kernel BUG at ../fs/fscache/operation.c:38!
seems to be caused by the object being removed from the cache before it has
even been added. I suspect that is being caused because creating the object
fails due to the lack of 'bmap'.
Is there any way you can mount some other filesystem on /var/cache/fscache?
You could possible create a large file somewhere, then
losetup /dev/loop0 /my/large/file
mkfs.ext4 /dev/loop0
mount /dev/loop0 /var/cache/fscache
Then restart cachefilesd.
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