On 7/27/20 5:19 PM, Andrew Morton wrote: > On Sat, 25 Jul 2020 16:07:49 +0800 Muchun Song <songmuc...@bytedance.com> > wrote: > >> In the reservation routine, we only check whether the cpuset meets >> the memory allocation requirements. But we ignore the mempolicy of >> MPOL_BIND case. If someone mmap hugetlb succeeds, but the subsequent >> memory allocation may fail due to mempolicy restrictions and receives >> the SIGBUS signal. This can be reproduced by the follow steps. >> >> 1) Compile the test case. >> cd tools/testing/selftests/vm/ >> gcc map_hugetlb.c -o map_hugetlb >> >> 2) Pre-allocate huge pages. Suppose there are 2 numa nodes in the >> system. Each node will pre-allocate one huge page. >> echo 2 > /proc/sys/vm/nr_hugepages >> >> 3) Run test case(mmap 4MB). We receive the SIGBUS signal. >> numactl --membind=0 ./map_hugetlb 4 >> >> With this patch applied, the mmap will fail in the step 3) and throw >> "mmap: Cannot allocate memory". > > This doesn't compile with CONFIG_NUMA=n - ther eis no implementation of > get_task_policy(). > > I think it needs more than a simple build fix - can we please rework > the patch so that its impact (mainly code size) on non-NUMA machines is > minimized?
I'll let Muchun see if there is a more elegant fix. However, a relatively simple build fix such as: diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 8069ca47c18c..4bfbddfee0d3 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3455,12 +3455,14 @@ static unsigned int allowed_mems_nr(struct hstate *h) { int node; unsigned int nr = 0; - struct mempolicy *mpol = get_task_policy(current); - nodemask_t *mpol_allowed; + nodemask_t *mpol_allowed = NULL; unsigned int *array = h->free_huge_pages_node; +#ifdef CONFIG_NUMA + struct mempolicy *mpol = get_task_policy(current); gfp_t gfp_mask = htlb_alloc_mask(h); mpol_allowed = policy_nodemask(gfp_mask, mpol); +#endif for_each_node_mask(node, cpuset_current_mems_allowed) { if (!mpol_allowed || Does not have much of an impact on code size. Here are the non-numa versions of the routine before Muchun's patch and after. Dump of assembler code for function cpuset_mems_nr: 0xffffffff8126a3a0 <+0>: callq 0xffffffff81060f80 <__fentry__> 0xffffffff8126a3a5 <+5>: xor %eax,%eax 0xffffffff8126a3a7 <+7>: mov %gs:0x17bc0,%rdx 0xffffffff8126a3b0 <+16>: testb $0x1,0x778(%rdx) 0xffffffff8126a3b7 <+23>: jne 0xffffffff8126a3ba <cpuset_mems_nr+26> 0xffffffff8126a3b9 <+25>: retq 0xffffffff8126a3ba <+26>: mov (%rdi),%eax 0xffffffff8126a3bc <+28>: retq End of assembler dump. Dump of assembler code for function allowed_mems_nr: 0xffffffff8126a3a0 <+0>: callq 0xffffffff81060f80 <__fentry__> 0xffffffff8126a3a5 <+5>: xor %eax,%eax 0xffffffff8126a3a7 <+7>: mov %gs:0x17bc0,%rdx 0xffffffff8126a3b0 <+16>: testb $0x1,0x778(%rdx) 0xffffffff8126a3b7 <+23>: jne 0xffffffff8126a3ba <allowed_mems_nr+26> 0xffffffff8126a3b9 <+25>: retq 0xffffffff8126a3ba <+26>: mov 0x6c(%rdi),%eax 0xffffffff8126a3bd <+29>: retq End of assembler dump. -- Mike Kravetz