linux-kernel - [PATCH] mm/khugepaged: alloc_charge_hpage() take care of mem charge errors

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Message-Id: <20230221214344.609226-1-peterx@redhat.com>
Date:   Tue, 21 Feb 2023 16:43:44 -0500
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>, peterx@...hat.com,
        Johannes Weiner <hannes@...xchg.org>,
        Yang Shi <shy828301@...il.com>,
        David Stevens <stevensd@...omium.org>, stable@...r.kernel.org
Subject: [PATCH] mm/khugepaged: alloc_charge_hpage() take care of mem charge errors

If memory charge failed, the caller shouldn't call mem_cgroup_uncharge().
Let alloc_charge_hpage() handle the error itself and clear hpage properly
if mem charge fails.

Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Yang Shi <shy828301@...il.com>
Cc: David Stevens <stevensd@...omium.org>
Cc: stable@...r.kernel.org
Fixes: 9d82c69438d0 ("mm: memcontrol: convert anon and file-thp to new mem_cgroup_charge() API")
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/khugepaged.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 8dbc39896811..941d1c7ea910 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1063,12 +1063,19 @@ static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
 	gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
 		     GFP_TRANSHUGE);
 	int node = hpage_collapse_find_target_node(cc);
+	struct folio *folio;
 
 	if (!hpage_collapse_alloc_page(hpage, gfp, node, &cc->alloc_nmask))
 		return SCAN_ALLOC_HUGE_PAGE_FAIL;
-	if (unlikely(mem_cgroup_charge(page_folio(*hpage), mm, gfp)))
+
+	folio = page_folio(*hpage);
+	if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
+		folio_put(folio);
+		*hpage = NULL;
 		return SCAN_CGROUP_CHARGE_FAIL;
+	}
 	count_memcg_page_event(*hpage, THP_COLLAPSE_ALLOC);
+
 	return SCAN_SUCCEED;
 }
 
-- 
2.39.1