On 17.10.23 09:28, David Hildenbrand wrote:
On 17.10.23 08:22, Mike Rapoport wrote:From: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx> Qi Zheng reports crashes in a production environment and provides a simplified example as a reproducer: For example, if we use qemu to start a two NUMA node kernel, one of the nodes has 2M memory (less than NODE_MIN_SIZE), and the other node has 2G, then we will encounter the following panic: [ 0.149844] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 0.150783] #PF: supervisor write access in kernel mode [ 0.151488] #PF: error_code(0x0002) - not-present page <...> [ 0.156056] RIP: 0010:_raw_spin_lock_irqsave+0x22/0x40 <...> [ 0.169781] Call Trace: [ 0.170159] <TASK> [ 0.170448] deactivate_slab+0x187/0x3c0 [ 0.171031] ? bootstrap+0x1b/0x10e [ 0.171559] ? preempt_count_sub+0x9/0xa0 [ 0.172145] ? kmem_cache_alloc+0x12c/0x440 [ 0.172735] ? bootstrap+0x1b/0x10e [ 0.173236] bootstrap+0x6b/0x10e [ 0.173720] kmem_cache_init+0x10a/0x188 [ 0.174240] start_kernel+0x415/0x6ac [ 0.174738] secondary_startup_64_no_verify+0xe0/0xeb [ 0.175417] </TASK> [ 0.175713] Modules linked in: [ 0.176117] CR2: 0000000000000000 The crashes happen because of inconsistency between nodemask that has nodes with less than 4MB as memoryless and the actual memory fed into core mm. The commit 9391a3f9c7f1 ("[PATCH] x86_64: Clear more state when ignoring empty node in SRAT parsing") that introduced minimal size of a NUMA node does not explain why a node size cannot be less than 4MB and what boot failures this restriction might fix. Since then a lot has changed and core mm won't confuse badly about small node sizes. Drop the limitation for the minimal node size. Reported-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> Signed-off-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Link: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@xxxxxxxxxxxxx/That's just a resend I assume? Or has anything changed?
Saw the other mail now, so just a resend. -- Cheers, David / dhildenb
