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mm/hugetlb: fix nodes huge page allocation when there are surplus pages 

commit b72b3c9c34c825c81d205241c5f822fc7835923f
Author: Xueshi Hu <xueshi.hu@smartx.com>
Date:   Tue Aug 29 11:33:43 2023 +0800

    mm/hugetlb: fix nodes huge page allocation when there are surplus pages

    In set_nr_huge_pages(), local variable "count" is used to record
    persistent_huge_pages(), but when it cames to nodes huge page allocation,
    the semantics changes to nr_huge_pages.  When there exists surplus huge
    pages and using the interface under
    /sys/devices/system/node/node*/hugepages to change huge page pool size,
    this difference can result in the allocation of an unexpected number of
    huge pages.

    Steps to reproduce the bug:

    Starting with:

                                      Node 0          Node 1    Total
            HugePages_Total             0.00            0.00     0.00
            HugePages_Free              0.00            0.00     0.00
            HugePages_Surp              0.00            0.00     0.00

    create 100 huge pages in Node 0 and consume it, then set Node 0 's
    nr_hugepages to 0.

    yields:

                                      Node 0          Node 1    Total
            HugePages_Total           200.00            0.00   200.00
            HugePages_Free              0.00            0.00     0.00
            HugePages_Surp            200.00            0.00   200.00

    write 100 to Node 1's nr_hugepages

                    echo 100 > /sys/devices/system/node/node1/\
            hugepages/hugepages-2048kB/nr_hugepages

    gets:

                                      Node 0          Node 1    Total
            HugePages_Total           200.00          400.00   600.00
            HugePages_Free              0.00          400.00   400.00
            HugePages_Surp            200.00            0.00   200.00

    Kernel is expected to create only 100 huge pages and it gives 200.

    Link: https://lkml.kernel.org/r/20230829033343.467779-1-xueshi.hu@smartx.com
    Fixes: 9a30523066 ("hugetlb: add per node hstate attributes")
    Signed-off-by: Xueshi Hu <xueshi.hu@smartx.com>
    Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Cc: Muchun Song <muchun.song@linux.dev>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

JIRA: https://issues.redhat.com/browse/RHEL-5619
Signed-off-by: Nico Pache <npache@redhat.com>
This commit is contained in:
Nico Pache 2024-04-15 19:04:20 -06:00
parent 5f4fd578a4
commit 734ceed97a
1 changed files with 3 additions and 1 deletions
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4
mm/hugetlb.c
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@ -3529,7 +3529,9 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
if (nid != NUMA_NO_NODE) {
unsigned long old_count = count;
count += h->nr_huge_pages - h->nr_huge_pages_node[nid];
count += persistent_huge_pages(h) -
(h->nr_huge_pages_node[nid] -
h->surplus_huge_pages_node[nid]);
/*
* User may have specified a large count value which caused the
* above calculation to overflow. In this case, they wanted