Re: [PATCH v3 1/4] hugetlb: Fix wrong use of nr_online_nodes

[Andrew Morton <akpm@linux-foundation.org>]

On Sat, 16 Apr 2022 09:21:45 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote:

> 
> On 2022/4/15 13:41, Kefeng Wang wrote:
> >
> > On 2022/4/15 10:09, Davidlohr Bueso wrote:
> >> On Wed, 13 Apr 2022, Peng Liu wrote:
> >>
> >>> Certain systems are designed to have sparse/discontiguous nodes. In
> >>> this case, nr_online_nodes can not be used to walk through numa node.
> >>> Also, a valid node may be greater than nr_online_nodes.
> >>>
> >>> However, in hugetlb, it is assumed that nodes are contiguous. Recheck
> >>> all the places that use nr_online_nodes, and repair them one by one.
> >>>
> >>> Suggested-by: David Hildenbrand <david@redhat.com>
> >>> Fixes: 4178158ef8ca ("hugetlbfs: fix issue of preallocation of 
> >>> gigantic pages can't work")
> >>> Fixes: b5389086ad7b ("hugetlbfs: extend the definition of hugepages 
> >>> parameter to support node allocation")
> >>> Fixes: e79ce9832316 ("hugetlbfs: fix a truncation issue in hugepages 
> >>> parameter")
> >>> Fixes: f9317f77a6e0 ("hugetlb: clean up potential spectre issue 
> >>> warnings")
> >>> Signed-off-by: Peng Liu <liupeng256@huawei.com>
> >>> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> >>> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> >>
> >> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
> >>
> >> ... but
> >>
> >>> ---
> >>> mm/hugetlb.c | 12 ++++++------
> >>> 1 file changed, 6 insertions(+), 6 deletions(-)
> >>>
> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> >>> index b34f50156f7e..5b5a2a5a742f 100644
> >>> --- a/mm/hugetlb.c
> >>> +++ b/mm/hugetlb.c
> >>> @@ -2979,7 +2979,7 @@ int __alloc_bootmem_huge_page(struct hstate 
> >>> *h, int nid)
> >>>     struct huge_bootmem_page *m = NULL; /* initialize for clang */
> >>>     int nr_nodes, node;
> >>>
> >>> -    if (nid != NUMA_NO_NODE && nid >= nr_online_nodes)
> >>> +    if (nid != NUMA_NO_NODE && !node_online(nid))
> >>
> >> afaict null_blk could also use this, actually the whole thing wants a
> >> helper - node_valid()?
> >>
> > This one should be unnecessary, and this patch looks has a bug,
> >
> > if a very nid passed to node_online(), it may crash,  could you 
> > re-check it,
> >
> > see my changes below,
> >
> > 1) add tmp check against MAX_NUMNODES before node_online() check,
> >
> >     and move it after get tmp in hugepages_setup() , this could cover 
> > both per-node alloc and normal alloc
> 
> sorry，for normal alloc, tmp is the number of huge pages, we don't  need 
> the movement,   only add tmp >= MAX_NUMNODES is ok
> 

Does the v4 patch address the issues which were raised in this thread?


--- a/mm/hugetlb.c~hugetlb-fix-wrong-use-of-nr_online_nodes-v4
+++ a/mm/hugetlb.c
@@ -2986,8 +2986,6 @@ int __alloc_bootmem_huge_page(struct hst
 	struct huge_bootmem_page *m = NULL; /* initialize for clang */
 	int nr_nodes, node;
 
-	if (nid != NUMA_NO_NODE && !node_online(nid))
-		return 0;
 	/* do node specific alloc */
 	if (nid != NUMA_NO_NODE) {
 		m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h),
@@ -4174,7 +4172,7 @@ static int __init hugepages_setup(char *
 				pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
 				return 0;
 			}
-			if (!node_online(tmp))
+			if (tmp >= MAX_NUMNODES || !node_online(tmp))
 				goto invalid;
 			node = array_index_nospec(tmp, MAX_NUMNODES);
 			p += count + 1;
_