From 8dc9cd7ff185e9bd98c3613492f2f1d0e29dda0d Mon Sep 17 00:00:00 2001 From: Aristeu Rozanski Date: Fri, 21 Jun 2024 15:00:50 -0400 Subject: [PATCH] hugetlb: force allocating surplus hugepages on mempolicy allowed nodes commit 003af997c8a945493859dd1a2d015cc9387ff27a upstream. When trying to allocate a hugepage with no reserved ones free, it may be allowed in case a number of overcommit hugepages was configured (using /proc/sys/vm/nr_overcommit_hugepages) and that number wasn't reached. This allows for a behavior of having extra hugepages allocated dynamically, if there're resources for it. Some sysadmins even prefer not reserving any hugepages and setting a big number of overcommit hugepages. But while attempting to allocate overcommit hugepages in a multi node system (either NUMA or mempolicy/cpuset) said allocations might randomly fail even when there're resources available for the allocation. This happens due to allowed_mems_nr() only accounting for the number of free hugepages in the nodes the current process belongs to and the surplus hugepage allocation is done so it can be allocated in any node. In case one or more of the requested surplus hugepages are allocated in a different node, the whole allocation will fail due allowed_mems_nr() returning a lower value. So allocate surplus hugepages in one of the nodes the current process belongs to. Easy way to reproduce this issue is to use a 2+ NUMA nodes system: # echo 0 >/proc/sys/vm/nr_hugepages # echo 1 >/proc/sys/vm/nr_overcommit_hugepages # numactl -m0 ./tools/testing/selftests/mm/map_hugetlb 2 Repeating the execution of map_hugetlb test application will eventually fail when the hugepage ends up allocated in a different node. [aris@ruivo.org: v2] Link: https://lkml.kernel.org/r/20240701212343.GG844599@cathedrallabs.org Link: https://lkml.kernel.org/r/20240621190050.mhxwb65zn37doegp@redhat.com Signed-off-by: Aristeu Rozanski Cc: Muchun Song Cc: Aristeu Rozanski Cc: David Hildenbrand Cc: Vishal Moola Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 159733989bc8c8c211644ba9b15dcc99132e9472) --- mm/hugetlb.c | 47 ++++++++++++++++++++++++++++------------------- 1 file changed, 28 insertions(+), 19 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 789decf5d11ba..d35c9e68fb489 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2518,6 +2518,23 @@ struct folio *alloc_hugetlb_folio_vma(struct hstate *h, struct vm_area_struct *v return folio; } +static nodemask_t *policy_mbind_nodemask(gfp_t gfp) +{ +#ifdef CONFIG_NUMA + struct mempolicy *mpol = get_task_policy(current); + + /* + * Only enforce MPOL_BIND policy which overlaps with cpuset policy + * (from policy_nodemask) specifically for hugetlb case + */ + if (mpol->mode == MPOL_BIND && + (apply_policy_zone(mpol, gfp_zone(gfp)) && + cpuset_nodemask_valid_mems_allowed(&mpol->nodes))) + return &mpol->nodes; +#endif + return NULL; +} + /* * Increase the hugetlb pool such that it can accommodate a reservation * of size 'delta'. @@ -2531,6 +2548,8 @@ static int gather_surplus_pages(struct hstate *h, long delta) long i; long needed, allocated; bool alloc_ok = true; + int node; + nodemask_t *mbind_nodemask = policy_mbind_nodemask(htlb_alloc_mask(h)); lockdep_assert_held(&hugetlb_lock); needed = (h->resv_huge_pages + delta) - h->free_huge_pages; @@ -2545,8 +2564,15 @@ static int gather_surplus_pages(struct hstate *h, long delta) retry: spin_unlock_irq(&hugetlb_lock); for (i = 0; i < needed; i++) { - folio = alloc_surplus_hugetlb_folio(h, htlb_alloc_mask(h), - NUMA_NO_NODE, NULL); + folio = NULL; + for_each_node_mask(node, cpuset_current_mems_allowed) { + if (!mbind_nodemask || node_isset(node, *mbind_nodemask)) { + folio = alloc_surplus_hugetlb_folio(h, htlb_alloc_mask(h), + node, NULL); + if (folio) + break; + } + } if (!folio) { alloc_ok = false; break; @@ -4531,23 +4557,6 @@ static int __init default_hugepagesz_setup(char *s) } __setup("default_hugepagesz=", default_hugepagesz_setup); -static nodemask_t *policy_mbind_nodemask(gfp_t gfp) -{ -#ifdef CONFIG_NUMA - struct mempolicy *mpol = get_task_policy(current); - - /* - * Only enforce MPOL_BIND policy which overlaps with cpuset policy - * (from policy_nodemask) specifically for hugetlb case - */ - if (mpol->mode == MPOL_BIND && - (apply_policy_zone(mpol, gfp_zone(gfp)) && - cpuset_nodemask_valid_mems_allowed(&mpol->nodes))) - return &mpol->nodes; -#endif - return NULL; -} - static unsigned int allowed_mems_nr(struct hstate *h) { int node;