This test does:
1. mount a volume
2. kill a brick in the volume
3. mkdir (/somedir)
In my local tests and in , I see that mkdir in step 3 fails because
there is no dht-layout on root directory.
The reason I think is by the time first lookup on "/" hit dht, a brick was
killed as per step 2. This means layout was not healed for "/" and since
this is a new volume, no layout is present on it. Note that the first
lookup done on "/" by fuse-bridge is not synchronized with parent process
of daemonized glusterfs mount completing. IOW, by the time glusterfs cmd
executed there is no guarantee that lookup on "/" is complete. So, if step
2 races ahead of fuse_first_lookup on "/", we end up with an invalid
dht-layout on "/" resulting in failures.
I've sent a patch  to fix this race condition.
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