Hi Cephers,
I'm using VSCode remote development with a docker server. It worked OK
but fails to start the debugger after /root mounted by ceph-fuse. The
log shows that the binary passes access X_OK check but cannot be
actually executed. see:
```
strace_log:
access("/root/.vscode-server/extensions/ms-vscode.cpptools-1.1.3/debugAdapters/OpenDebugAD7",
X_OK) = 0
root@develop:~# ls -alh
.vscode-server/extensions/ms-vscode.cpptools-1.1.3/debugAdapters/OpenDebugAD7
-rw-r--r-- 1 root root 978 Dec 10 13:06
.vscode-server/extensions/ms-vscode.cpptools-1.1.3/debugAdapters/OpenDebugAD7
```
I also test the access syscall on ext4, xfs and even cephfs kernel
client, all of them return -EACCES, which is expected (the extension
will then explicitly call chmod +x).
After some digging in the code, I found it is probably caused by
https://github.com/ceph/ceph/blob/master/src/client/Client.cc#L5549-L5550.
So here come two questions:
1. Is this a bug or is there any concern I missed?
2. It works again with fuse_default_permissions=true, any drawbacks if
this option is set?