From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D62D252ED5E; Wed, 9 Sep 2026 13:56:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788962214; cv=none; b=svKH21weyhR02e0WZ0etmEcdiHru/r/PnC3C6rWaizIhwzsXtZGub+L7f999r2JNuSMCeXNye3eTTNyaVV0nvywM4Kz1DeZcJQfYgzrmSKSEpYWDaADLo/8n8VT4Uh8TLFG7bRR3vEn2HFNUMVJf6bepr2GEqoUeaUd/8ASQaGA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788962214; c=relaxed/simple; bh=f4WVBCD/jyHSlOojpj8YL5BlINFkFX74guoghyK5qNk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MmSzGHw3u6YkxRLgmR4x4zfcnmbO7J8H/vjoEDh6cGlyGtUTOo+sfptVp9WQitu72MciByor4eT9gfd8J3foLxYLnM5He05IcAgocUsunH28xomH99K3RymCaf8rW4WYF7my+to9wjrtz7OfB3FBiiXGARqp1BCFUhWRQz+Eu7k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=anheWdzw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="anheWdzw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38C281F00A3A; Wed, 9 Sep 2026 13:56:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788962212; bh=X/qLzFuMDTMmYtrOz4kj5iZzWsu6D7clAbYZxpVi5Bo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=anheWdzwxLNzlQP/eo823JDBJRf1cpKUf5FUyyje/HWZFfve+NzYtTUZyxWgMe194 io8cbzYPZtwJjGeQjR8GZtqroqIe2VBUPWabpS0mcLvZ1UmLzCIV/aQHm76l+J2/tL OJviKgYOo4jqHH5CFhri0ychpn3AgI80Phy1WnEc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Longlong Xia , Muchun Song , David Hildenbrand , Jinjiang Tu , Oscar Salvador , Andrew Morton Subject: [PATCH 7.2 172/556] mm/hugetlb: keep max_huge_pages when dissolving surplus folios Date: Wed, 9 Sep 2026 15:37:32 +0200 Message-ID: <20260909134236.470696012@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909134230.441546314@linuxfoundation.org> References: <20260909134230.441546314@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Longlong Xia commit 267bede12d3b108ca29997ce280e927a570ec97f upstream. dissolve_free_hugetlb_folio() can remove a free folio as surplus when its node has surplus pages. In that case remove_hugetlb_folio() decrements both nr_huge_pages and surplus_huge_pages, leaving the persistent pool size unchanged. Updating max_huge_pages as if a persistent folio had been removed can therefore corrupt the persistent pool target and underflow it when max_huge_pages is zero. Keep max_huge_pages unchanged for surplus folios, including the vmemmap restoration rollback path. Link: https://lore.kernel.org/20260814083027.1419487-1-xialonglong2025@163.com Fixes: cb402bbdabca ("mm/hugetlb: fix surplus pages in dissolve_free_huge_page()") Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Longlong Xia Reviewed-by: Muchun Song Cc: David Hildenbrand Cc: Jinjiang Tu Cc: Longlong Xia Cc: Oscar Salvador Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2002,7 +2002,8 @@ retry: if (h->surplus_huge_pages_node[folio_nid(folio)]) adjust_surplus = true; remove_hugetlb_folio(h, folio, adjust_surplus); - h->max_huge_pages--; + if (!adjust_surplus) + h->max_huge_pages--; spin_unlock_irq(&hugetlb_lock); /* @@ -2022,7 +2023,8 @@ retry: if (rc) { spin_lock_irq(&hugetlb_lock); add_hugetlb_folio(h, folio, adjust_surplus); - h->max_huge_pages++; + if (!adjust_surplus) + h->max_huge_pages++; goto out; } } else {