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-rw-r--r--mm/hugetlb.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 88e708b..eb7180d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -174,6 +174,17 @@ static int __init hugetlb_setup(char *s)
}
__setup("hugepages=", hugetlb_setup);
+static unsigned int cpuset_mems_nr(unsigned int *array)
+{
+ int node;
+ unsigned int nr = 0;
+
+ for_each_node_mask(node, cpuset_current_mems_allowed)
+ nr += array[node];
+
+ return nr;
+}
+
#ifdef CONFIG_SYSCTL
static void update_and_free_page(struct page *page)
{
@@ -819,6 +830,26 @@ int hugetlb_reserve_pages(struct inode *inode, long from, long to)
chg = region_chg(&inode->i_mapping->private_list, from, to);
if (chg < 0)
return chg;
+ /*
+ * When cpuset is configured, it breaks the strict hugetlb page
+ * reservation as the accounting is done on a global variable. Such
+ * reservation is completely rubbish in the presence of cpuset because
+ * the reservation is not checked against page availability for the
+ * current cpuset. Application can still potentially OOM'ed by kernel
+ * with lack of free htlb page in cpuset that the task is in.
+ * Attempt to enforce strict accounting with cpuset is almost
+ * impossible (or too ugly) because cpuset is too fluid that
+ * task or memory node can be dynamically moved between cpusets.
+ *
+ * The change of semantics for shared hugetlb mapping with cpuset is
+ * undesirable. However, in order to preserve some of the semantics,
+ * we fall back to check against current free page availability as
+ * a best attempt and hopefully to minimize the impact of changing
+ * semantics that cpuset has.
+ */
+ if (chg > cpuset_mems_nr(free_huge_pages_node))
+ return -ENOMEM;
+
ret = hugetlb_acct_memory(chg);
if (ret < 0)
return ret;
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