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

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On 2022/4/19 12:40, Andrew Morton wrote:
On Sat, 16 Apr 2022 09:21:45 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> 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@xxxxxxxxxx>
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@xxxxxxxxxx>
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>

... 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?
Yes, v4 has fix this.


--- 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;
_

.





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