Edenmal

Sysadmin Garden of Eden

SteamCMD: Not working on CephFS

See title.

Yes, you read right. SteamCMD is not working on CephFS (and maybe GlusterFS too, I can’t test it on GlusterFS ).
The reason for that is a “failing” getdents when on the CephFS.
A colleague told me that error may be related to the st_size and the rbytes of CephFS.

strace on xfs filesystem:

[...]
[pid 123] stat64("./zip0.zip", 0xf71c9c40) = -1 ENOENT (No such file or directory)
[pid 123] open(".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = 2
[pid 123] fstat64(2, {st_mode=S_IFDIR|0755, st_size=100, ...}) = 0
[pid 123] getdents(2, /* 7 entries */, 32768) = 152
[pid 123] getdents(2, /* 0 entries */, 32768) = 0
[pid 123] close(2)
[...]

strace on CephFS:

[...]
[pid 123] stat64("./zip0.zip", 0xf720ac40) = -1 ENOENT (No such file or directory)
[pid 123] open(".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY|O_CLOEXEC) = 2
[pid 123] fstat64(2, {st_mode=S_IFDIR|0755, st_size=5, ...}) = 0
[pid 123] getdents(2, 0xf7002114, 65536) = -1 EOVERFLOW (Value too large for defined data type)
[pid 123] close(2)
[...]

As you can see the st_size on the xfs filesystem reported is higher (100).
The third parameter (unsigned int count from getdents man page), comes as a result from the “weird” st_size, given to the getdents() function is lower 32768 than the int 65536 on the CephFS.

In C an unsigned short int can only be 65535 max, but 65536 got returned..

Next I tried to look into the rbytes that a colleague mentioned.
And guess what I found looking for a way to disable/fix/modify the st_size from CephFS.
I found out that the documented rbytes and for me interesting norbytes mount option.
When looking at the docs we see that both mount options are documented: http://docs.ceph.com/docs/hammer/man/8/mount.ceph/#options
I used GitHub’s code search but the only occurrences I found are in the man page files.

I have directly created an issue at the Ceph’s Bugtracker to see if it is an issue in my setup or really a missing feature in Ceph. For the interested here is the link to the issue: http://tracker.ceph.com/issues/16738.