Repeated fork() call causes anon_vma_chain and anon_vma slabs to grow result in kernel panic due to out of memory (OOM).

Issue

• Repeated fork() call causes anon_vma_chain and anon_vma slabs to grow result in kernel panic due to out of memory (OOM).
• Kernel panic due to out of memory (OOM) even though none of the applications running on the system are using memory.

[28247418.855000] Mem-Info:
[28247418.855000] Node 0 DMA per-cpu:
[28247418.855000] CPU    0: hi:    0, btch:   1 usd:   0
[28247418.855000] CPU    1: hi:    0, btch:   1 usd:   0
[28247418.855000] Node 0 DMA32 per-cpu:
[28247418.855000] CPU    0: hi:  186, btch:  31 usd:   0
[28247418.855000] CPU    1: hi:  186, btch:  31 usd:   0
[28247418.855000] Node 0 Normal per-cpu:
[28247418.855000] CPU    0: hi:  186, btch:  31 usd:  30
[28247418.855000] CPU    1: hi:  186, btch:  31 usd:   1
[28247418.856000] active_anon:0 inactive_anon:0 isolated_anon:0
[28247418.856000]  active_file:0 inactive_file:34 isolated_file:0
[28247418.856000]  unevictable:0 dirty:0 writeback:0 unstable:0
[28247418.856000]  free:21755 slab_reclaimable:2713 slab_unreclaimable:911997
[28247418.856000]  mapped:3 shmem:0 pagetables:17201 bounce:0
[28247418.856000] Node 0 DMA free:15684kB min:248kB low:308kB high:372kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15292kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes
[28247418.857000] lowmem_reserve[]: 0 3000 4010 4010
[28247418.857000] Node 0 DMA32 free:54400kB min:50372kB low:62964kB high:75556kB active_anon:0kB inactive_anon:0kB active_file:16kB inactive_file:8kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:3072160kB mlocked:0kB dirty:0kB writeback:0kB mapped:4kB shmem:0kB slab_reclaimable:3080kB slab_unreclaimable:2726876kB kernel_stack:7936kB pagetables:45272kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:34 all_unreclaimable? no
[28247418.857000] lowmem_reserve[]: 0 0 1010 1010
[28247418.857000] Node 0 Normal free:16936kB min:16956kB low:21192kB high:25432kB active_anon:0kB inactive_anon:0kB active_file:48kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:1034240kB mlocked:0kB dirty:0kB writeback:0kB mapped:8kB shmem:0kB slab_reclaimable:7772kB slab_unreclaimable:921112kB kernel_stack:3688kB pagetables:23532kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:4954 all_unreclaimable? no
[28247418.858000] lowmem_reserve[]: 0 0 0 0
[28247418.858000] Node 0 DMA: 1*4kB 4*8kB 2*16kB 2*32kB 3*64kB 0*128kB 0*256kB 0*512kB 1*1024kB 1*2048kB 3*4096kB = 15684kB
[28247418.858000] Node 0 DMA32: 1061*4kB 1258*8kB 789*16kB 274*32kB 67*64kB 25*128kB 2*256kB 1*512kB 0*1024kB 5*2048kB 0*4096kB = 54452kB
[28247418.858000] Node 0 Normal: 3133*4kB 33*8kB 7*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 1*4096kB = 17004kB
[28247418.858000] 80 total pagecache pages
[28247418.859000] 18 pages in swap cache
[28247418.859000] Swap cache stats: add 5359942, delete 5359924, find 3103057/4532171
[28247418.859000] Free swap  = 5505444kB
[28247418.859000] Total swap = 6291448kB
[28247418.883000] 1048560 pages RAM
[28247418.883000] 67108 pages reserved
[28247418.883000] 263 pages shared
[28247418.883000] 953718 pages non-shared