[patch 037/143] mm/hugeltb: handle the error case in hugetlb_fix_reserve_counts()

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From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Subject: mm/hugeltb: handle the error case in hugetlb_fix_reserve_counts()

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.

Link: https://lkml.kernel.org/r/20210410072348.20437-5-linmiaohe@xxxxxxxxxx
Fixes: b5cec28d36f5 ("hugetlbfs: truncate_hugepages() takes a range of pages")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Feilong Lin <linfeilong@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/hugetlb.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/mm/hugetlb.c~mm-hugeltb-handle-the-error-case-in-hugetlb_fix_reserve_counts
+++ a/mm/hugetlb.c
@@ -742,13 +742,20 @@ void hugetlb_fix_reserve_counts(struct i
 {
 	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");
 }
 
 /*
_



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