[PATCH v2 4/5] mm/hugeltb: handle the error case in hugetlb_fix_reserve_counts()

[Miaohe Lin <linmiaohe@huawei.com>]

A rare out of memory error would prevent removal of the reserve map region
for a page. hugetlb_fix_reserve_counts() handles this rare case to avoid
dangling with incorrect counts. Unfortunately, hugepage_subpool_get_pages
and hugetlb_acct_memory could possibly fail too. We should correctly handle
these cases.

Fixes: b5cec28d36f5 ("hugetlbfs: truncate_hugepages() takes a range of pages")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/hugetlb.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 387c9a62615e..a14bb1a03ee4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -745,13 +745,20 @@ void hugetlb_fix_reserve_counts(struct inode *inode)
 {
 	struct hugepage_subpool *spool = subpool_inode(inode);
 	long rsv_adjust;
+	bool reserved = false;
 
 	rsv_adjust = hugepage_subpool_get_pages(spool, 1);
-	if (rsv_adjust) {
+	if (rsv_adjust > 0) {
 		struct hstate *h = hstate_inode(inode);
 
-		hugetlb_acct_memory(h, 1);
+		if (!hugetlb_acct_memory(h, 1))
+			reserved = true;
+	} else if (!rsv_adjust) {
+		reserved = true;
 	}
+
+	if (!reserved)
+		pr_warn("hugetlb: Huge Page Reserved count may go negative.\n");
 }
 
 /*
-- 
2.19.1