mm/hugetlb: fix missing call to restore_reserve_on_error()

When huge_add_to_page_cache() fails, the page is freed directly without
calling restore_reserve_on_error() to restore reserve for newly allocated
pages not in page cache.  Fix this by calling restore_reserve_on_error()
when huge_add_to_page_cache fails.

[[email protected]: remove err == -EEXIST check and retry logic]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Mike Kravetz <[email protected]>
Cc: Muchun Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 8 insertions, 3 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ff991e5bdf1f..8d52827d9f51 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5563,7 +5563,6 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
 	if (idx >= size)
 		goto out;
 
-retry:
 	new_page = false;
 	page = find_lock_page(mapping, idx);
 	if (!page) {
@@ -5603,9 +5602,15 @@ retry:
 		if (vma->vm_flags & VM_MAYSHARE) {
 			int err = huge_add_to_page_cache(page, mapping, idx);
 			if (err) {
+				/*
+				 * err can't be -EEXIST which implies someone
+				 * else consumed the reservation since hugetlb
+				 * fault mutex is held when add a hugetlb page
+				 * to the page cache. So it's safe to call
+				 * restore_reserve_on_error() here.
+				 */
+				restore_reserve_on_error(h, vma, haddr, page);
 				put_page(page);
-				if (err == -EEXIST)
-					goto retry;
 				goto out;
 			}
 			new_pagecache_page = true;