On Fri 24-07-20 18:03:06, 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 <guojianchao@xxxxxxxxxxxxx>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
>
> changelog in v2:
> 1) Reuse policy_nodemask().
>
> include/linux/mempolicy.h | 1 +
> mm/hugetlb.c | 19 ++++++++++++++++---
> mm/mempolicy.c | 2 +-
> 3 files changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
> index ea9c15b60a96..6b9640f1c990 100644
> --- a/include/linux/mempolicy.h
> +++ b/include/linux/mempolicy.h
> @@ -152,6 +152,7 @@ extern int huge_node(struct vm_area_struct *vma,
> extern bool init_nodemask_of_mempolicy(nodemask_t *mask);
> extern bool mempolicy_nodemask_intersects(struct task_struct *tsk,
> const nodemask_t *mask);
> +extern nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *policy);
> extern unsigned int mempolicy_slab_node(void);
>
> extern enum zone_type policy_zone;
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 589c330df4db..a753fe8591b4 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3463,12 +3463,25 @@ static int __init default_hugepagesz_setup(char *s)
> }
> __setup("default_hugepagesz=", default_hugepagesz_setup);
>
> -static unsigned int cpuset_mems_nr(unsigned int *array)
> +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, *mems_allowed, nodemask;
> + unsigned int *array = h->free_huge_pages_node;
> + gfp_t gfp_mask = htlb_alloc_mask(h);
> +
> + mpol_allowed = policy_nodemask(gfp_mask, mpol);
> + if (mpol_allowed) {
> + nodes_and(nodemask, cpuset_current_mems_allowed,
> + *mpol_allowed);
> + mems_allowed = &nodemask;
> + } else {
> + mems_allowed = &cpuset_current_mems_allowed;
> + }
I believe you can simplify this and use a similar pattern as the page
allocator. Something like
for_each_node_mask(node, mpol_allowed) {
if (node_isset(node, &cpuset_current_mems_allowed))
nr += array[node];
}
There shouldn't be any need to allocate a potentially large nodemask on
the stack.
--
Michal Hocko
SUSE Labs
