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 E059D52ED21; Wed, 30 Sep 2026 17:49:53 +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=1790790595; cv=none; b=nPlB26UOMFM0ZSX2MvxYRGXmIOy0AC9pFz8CuiTL4dy7qdLm7/ZChBBPn5QwabiuRz0q9sJF2FCPD1k6BKSK104eTzKELWR1nljp8CflukgBcM4fd/TEEGSMGlp2YXTJxkqIxLHxnCAB4ntoPt7HxcXGNKpUyF7VB1gjfHErQIs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790790595; c=relaxed/simple; bh=XkMlMF+LJ/uYGUZrc1M172Fof8v2HzdluntJClAG+kg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QPw/2gQp8pv7IE46rZJZXs5C1wz7vaumu6Pkqn02N4sysKy1yBvP4GwwboCsJhocMDOQBD7oOTzRw+Wj285vsKs249r8FZRKDpVro+RYoxlGiNtsxURgBVR492/GLCCyUVDbLhbBvc2XpAtaYeFMZ/6Rwq9FRz50LHJb6GrWsk4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=YHSk8VbU; 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="YHSk8VbU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C1211F000FF; Wed, 30 Sep 2026 17:49:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790790593; bh=/S0rBlHAbnCUiZJIc4AnPh3QeaXekzDJtaR1j8RwBeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=YHSk8VbURAa6RYDyxhKptfAoFBRP0Hvmki2MG85JGFkM1YsfwbrtuwzUlZxel85yw wg1H5OBU0ovZan7ZRadhPJwkf99v7PaPqUbr17ovQXViuq7B8Smr4kMeoRl1LaZo6L aSPGb5PMeBCXavj9yK3q5eq8UkqfHmX1udxQ+mos= 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 6.12 877/877] mm/hugetlb: keep max_huge_pages when dissolving surplus folios Date: Wed, 30 Sep 2026 17:29:48 +0200 Message-ID: <20260930152433.658484329@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152414.738996857@linuxfoundation.org> References: <20260930152414.738996857@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 6.12-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 @@ -2248,7 +2248,8 @@ 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); /* @@ -2268,7 +2269,8 @@ 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