On 2019/11/27 19:47, Michal Hocko wrote: > On Wed 27-11-19 18:28:00, Kefeng Wang wrote: >> The start_pfn and end_pfn are already available in move_freepages_block(), >> pfn_valid_within() should validate pfn first before touching the page, >> or we might access an unitialized page with CONFIG_HOLES_IN_ZONE configs. >> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: Michal Hocko <mhocko@xxxxxxxx> >> Cc: Vlastimil Babka <vbabka@xxxxxxx> >> Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> >> --- >> >> Here is an oops in 4.4(arm64 enabled CONFIG_HOLES_IN_ZONE), > > Is this reproducible with the current upstream kernel? There were large > changes in this aread since 4.4 Our inner tester found this oops twice, but couldn't be reproduced for now, even in 4.4 kernel, still trying... But the page_to_pfn() shouldn't be used in move_freepages(), right? ; ) > > Btw. the below should be part of the changelog. Ok, will resend. > >> Unable to handle kernel NULL pointer dereference at virtual address 00000000 >> pgd = ffffff8008f7e000 >> [00000000] *pgd=0000000017ffe003, *pud=0000000017ffe003, *pmd=0000000000000000 >> Internal error: Oops: 96000007 [#1] SMP >> CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W O 4.4.185 #1 >> >> PC is at move_freepages+0x80/0x10c >> LR is at move_freepages_block+0xd4/0xf4 >> pc : [<ffffff80083332e8>] lr : [<ffffff8008333448>] pstate: 80000085 >> [...] >> [<ffffff80083332e8>] move_freepages+0x80/0x10c >> [<ffffff8008333448>] move_freepages_block+0xd4/0xf4 >> [<ffffff8008335414>] __rmqueue+0x2bc/0x44c >> [<ffffff800833580c>] get_page_from_freelist+0x268/0x600 >> [<ffffff8008335e84>] __alloc_pages_nodemask+0x184/0x88c >> [<ffffff800837fae8>] new_slab+0xd0/0x494 >> [<ffffff8008381834>] ___slab_alloc.constprop.29+0x1c8/0x2e8 >> [<ffffff80083819a8>] __slab_alloc.constprop.28+0x54/0x84 >> [<ffffff8008381e68>] kmem_cache_alloc+0x64/0x198 >> [<ffffff80085b04e0>] __build_skb+0x44/0xa4 >> [<ffffff80085b06e4>] __netdev_alloc_skb+0xe4/0x134 >> \
