linux-kernel - [PATCH] mm: hugetlb: fix hugetlb allocation failure when handling freed or in-use hugetlb

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Message-Id: <b2e6ce111400670d8021baf4d7ac524ae78a40d5.1707105047.git.baolin.wang@linux.alibaba.com>
Date: Mon,  5 Feb 2024 11:54:17 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org,
	muchun.song@...ux.dev
Cc: osalvador@...e.de,
	david@...hat.com,
	mhocko@...nel.org,
	baolin.wang@...ux.alibaba.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mm: hugetlb: fix hugetlb allocation failure when handling freed or in-use hugetlb

When handling the freed hugetlb or in-use hugetlb, we should ignore the
failure of alloc_buddy_hugetlb_folio() to dissolve the old hugetlb successfully,
since we did not use the new allocated hugetlb in this 2 cases.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 mm/hugetlb.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9d996fe4ecd9..212ab331d355 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3042,9 +3042,8 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h,
 	 * under the lock.
 	 */
 	new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid, NULL, NULL);
-	if (!new_folio)
-		return -ENOMEM;
-	__prep_new_hugetlb_folio(h, new_folio);
+	if (new_folio)
+		__prep_new_hugetlb_folio(h, new_folio);
 
 retry:
 	spin_lock_irq(&hugetlb_lock);
@@ -3075,6 +3074,11 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h,
 		cond_resched();
 		goto retry;
 	} else {
+		if (!new_folio) {
+			ret = -ENOMEM;
+			goto free_new;
+		}
+
 		/*
 		 * Ok, old_folio is still a genuine free hugepage. Remove it from
 		 * the freelist and decrease the counters. These will be
@@ -3102,9 +3106,11 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h,
 
 free_new:
 	spin_unlock_irq(&hugetlb_lock);
-	/* Folio has a zero ref count, but needs a ref to be freed */
-	folio_ref_unfreeze(new_folio, 1);
-	update_and_free_hugetlb_folio(h, new_folio, false);
+	if (new_folio) {
+		/* Folio has a zero ref count, but needs a ref to be freed */
+		folio_ref_unfreeze(new_folio, 1);
+		update_and_free_hugetlb_folio(h, new_folio, false);
+	}
 
 	return ret;
 }
-- 
2.39.3