RHEL6: OOM panic on NFS4 server due to slab memory leak in nfsd4_stateowners

Issue

• Our customer's system experienced the OOM panic.

2016-03-01 05:06:36        PANIC: "Kernel panic - not syncing: Out of memory: system-wide panic_on_oom is enabled"

• We suspect the memory leak in the nfsd4_stateowners slab. The memory usage is here:

2016-03-01 05:06:29 crash> kmem -i
2016-03-01 05:06:30               PAGES        TOTAL      PERCENTAGE
2016-03-01 05:06:30  TOTAL MEM  1980946       7.6 GB         ----
2016-03-01 05:06:30       FREE    25748     100.6 MB    1% of TOTAL MEM
2016-03-01 05:06:30       USED  1955198       7.5 GB   98% of TOTAL MEM
2016-03-01 05:06:30     SHARED     4387      17.1 MB    0% of TOTAL MEM
2016-03-01 05:06:30    BUFFERS      528       2.1 MB    0% of TOTAL MEM
2016-03-01 05:06:30     CACHED     7331      28.6 MB    0% of TOTAL MEM
2016-03-01 05:06:30       SLAB  1912825       7.3 GB   96% of TOTAL MEM
                                              ^^^^^^