From: Mike Kravetz mike.kravetz@oracle.com
commit 79aa925bf239c234be8586780e482872dc4690dd upstream.
Michal Privoznik was using "free page reporting" in QEMU/virtio-balloon with hugetlbfs and hit the warning below. QEMU with free page hinting uses fallocate(FALLOC_FL_PUNCH_HOLE) to discard pages that are reported as free by a VM. The reporting granularity is in pageblock granularity. So when the guest reports 2M chunks, we fallocate(FALLOC_FL_PUNCH_HOLE) one huge page in QEMU.
WARNING: CPU: 7 PID: 6636 at mm/page_counter.c:57 page_counter_uncharge+0x4b/0x50 Modules linked in: ... CPU: 7 PID: 6636 Comm: qemu-system-x86 Not tainted 5.9.0 #137 Hardware name: Gigabyte Technology Co., Ltd. X570 AORUS PRO/X570 AORUS PRO, BIOS F21 07/31/2020 RIP: 0010:page_counter_uncharge+0x4b/0x50 ... Call Trace: hugetlb_cgroup_uncharge_file_region+0x4b/0x80 region_del+0x1d3/0x300 hugetlb_unreserve_pages+0x39/0xb0 remove_inode_hugepages+0x1a8/0x3d0 hugetlbfs_fallocate+0x3c4/0x5c0 vfs_fallocate+0x146/0x290 __x64_sys_fallocate+0x3e/0x70 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Investigation of the issue uncovered bugs in hugetlb cgroup reservation accounting. This patch addresses the found issues.
Fixes: 075a61d07a8e ("hugetlb_cgroup: add accounting for shared mappings") Reported-by: Michal Privoznik mprivozn@redhat.com Co-developed-by: David Hildenbrand david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Tested-by: Michal Privoznik mprivozn@redhat.com Reviewed-by: Mina Almasry almasrymina@google.com Acked-by: Michael S. Tsirkin mst@redhat.com Cc: stable@vger.kernel.org Cc: David Hildenbrand david@redhat.com Cc: Michal Hocko mhocko@kernel.org Cc: Muchun Song songmuchun@bytedance.com Cc: "Aneesh Kumar K . V" aneesh.kumar@linux.vnet.ibm.com Cc: Tejun Heo tj@kernel.org Link: https://lkml.kernel.org/r/20201021204426.36069-1-mike.kravetz@oracle.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/hugetlb.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
--- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -655,6 +655,8 @@ retry: }
del += t - f; + hugetlb_cgroup_uncharge_file_region( + resv, rg, t - f);
/* New entry for end of split region */ nrg->from = t; @@ -667,9 +669,6 @@ retry: /* Original entry is trimmed */ rg->to = f;
- hugetlb_cgroup_uncharge_file_region( - resv, rg, nrg->to - nrg->from); - list_add(&nrg->link, &rg->link); nrg = NULL; break; @@ -685,17 +684,17 @@ retry: }
if (f <= rg->from) { /* Trim beginning of region */ - del += t - rg->from; - rg->from = t; - hugetlb_cgroup_uncharge_file_region(resv, rg, t - rg->from); - } else { /* Trim end of region */ - del += rg->to - f; - rg->to = f;
+ del += t - rg->from; + rg->from = t; + } else { /* Trim end of region */ hugetlb_cgroup_uncharge_file_region(resv, rg, rg->to - f); + + del += rg->to - f; + rg->to = f; } }
@@ -2454,6 +2453,9 @@ struct page *alloc_huge_page(struct vm_a
rsv_adjust = hugepage_subpool_put_pages(spool, 1); hugetlb_acct_memory(h, -rsv_adjust); + if (deferred_reserve) + hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h), + pages_per_huge_page(h), page); } return page;