linux-kernel - [PATCH v2 3/6] mm/hugetlb: fix missing call to restore_reserve_on

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Date:   Tue, 23 Aug 2022 11:02:06 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>,
        <songmuchun@...edance.com>
CC:     <lukas.bulwahn@...il.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH v2 3/6] 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.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/hugetlb.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d46dfe5ba62c..8e62da153c64 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5576,7 +5576,6 @@ 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) {
@@ -5616,9 +5615,15 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
 		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;
-- 
2.23.0