Ceph

Fixed a few different bugs in this area, although we haven't specifically figured out why Jim was seeing that weird hang in his workload.

I noticed that btrfs tends to freeze quite often when I use a journal within the osd tree, or within a separate ods's filesystem. Not using a journal seems to alleviate the problem somewhat, but it still freezes every now and then. Kernels that exhibited this behavior, with ceph 0.24.3 and 0.25.1, were:

kernel-libre-2.6.35.10-74.fc14.1.x86_64
 kernel-libre-2.6.35.11-83.fc14.x86_64
 kernel-libre-2.6.38-0.rc8.git2.1.fc15.x86_64

A kernel that did NOT exhibit this problem (tested with 0.24.3 only) was:

kernel-libre-2.6.34.8-68.fc13.x86_64

I happen to maintain both the mon and an osd tree on a btrfs shared with other data, and other osds in stand-alone filesystems, and the problem seems to occur more often on the shared ones, particularly those most often modified by applications that take care of fsyncing files. That's all I've been able to gather so far.