The resv_map could be NULL since this routine can be called in the evict
inode path for all hugetlbfs inodes and we will have chg = 0 in this case.
But (chg - freed) won't go negative as Mike pointed out:
"If resv_map is NULL, then no hugetlb pages can be allocated/associated
with the file. As a result, remove_inode_hugepages will never find any
huge pages associated with the inode and the passed value 'freed' will
always be zero."
Add a comment clarifying this to make it clear and also avoid confusion.
Signed-off-by: Miaohe Lin <linmia...@huawei.com>
---
mm/hugetlb.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9b4c05699a90..387c9a62615e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5435,6 +5435,9 @@ long hugetlb_unreserve_pages(struct inode *inode, long
start, long end,
/*
* If the subpool has a minimum size, the number of global
* reservations to be released may be adjusted.
+ *
+ * Note that !resv_map implies freed == 0. So (chg - freed)
+ * won't go negative.
*/
gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed));
hugetlb_acct_memory(h, -gbl_reserve);
--
2.19.1
