On 7/24/20 3:03 AM, Muchun Song 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".
>
> Reported-by: Jianchao Guo <[email protected]>
> Signed-off-by: Muchun Song <[email protected]>
Michal has already provides some good suggestions.
> @@ -3653,7 +3666,7 @@ static int hugetlb_acct_memory(struct hstate *h, long
> delta)
> if (gather_surplus_pages(h, delta) < 0)
> goto out;
>
> - if (delta > cpuset_mems_nr(h->free_huge_pages_node)) {
> + if (delta > allowed_mems_nr(h)) {
> return_unused_surplus_pages(h, delta);
> goto out;
> }
There is a big comment before this code in hugetlb_acct_memory. The comment
only talks about cpusets. We should probably update that to include mempolicy
as well. It could be as simple as s/cpuset/cpuset or mempolicy/.
--
Mike Kravetz
