jbd slab cache creation / deletion race patches differ between Red Hat Enterprise Linux 5 and Red Hat Enterprise Linux 6

Issue

• The jbd slab cache creation/deletion is racy.  If multiple jbd based filesystems are mounted concurrently, and there are no other jbd based filesystems already mounted,  then a race condition can occur when creating the slab caches since jbd_slab[] is not locked.

• Patches were comitted for Red Hat Enteprise Linux 5 and Red Hat Enterprise Linux 6, but, there have been some concerns about the Red Hat Enterprise Linux 6 version of the patch, which is slightly different.  

• The concern is whether or not the patches that were put into jdb_slab_{alloc,free, lock} for the Red Hat Enterprise Linux 5 version of the problem are needed for the Red Hat Enterprise Linux 6.