From nobody Wed Dec 17 16:12:52 2025 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (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 C7E9F38DE0 for ; Sat, 14 Dec 2024 10:47:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734173273; cv=none; b=ahCo9ZNuxU1YZn1w0VLUDYQ3GPqG7c1yf+wtU21XVaWZ3X4iKQGd5FIWgwTL1qBb/gT5InWmUInBrP84h7AojcRmIXvn1PD7TYnv6WlMAgZvBElfn0seat0Oc7Si8f88uGgb+agz6s50sxty1yR/0XIGRn6xc+/xqdR1oQSUp7k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734173273; c=relaxed/simple; bh=WI1t+qPQepVOc9F7iAQQLRwd7ofgmLKsE25bDBKVN74=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=GUfMlPH3QkArV84D6EMtivoNDwLO2KTWkwjIB5vKRxGd7K5I85FQDMCWeg2f2XyGCoDs7l9h5gptyb4crY503YjXR1IszXXb5v1IaEpvbeX1pVPcCcex+RludJldWUqJ8XizowpCG/zeLB5MjAX3XViRAiFJ5qEIaaA5NmPVu5E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.163]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Y9NBs59rYz2DhRj; Sat, 14 Dec 2024 18:45:09 +0800 (CST) Received: from kwepemg200013.china.huawei.com (unknown [7.202.181.64]) by mail.maildlp.com (Postfix) with ESMTPS id 57907180044; Sat, 14 Dec 2024 18:47:39 +0800 (CST) Received: from huawei.com (10.175.113.32) by kwepemg200013.china.huawei.com (7.202.181.64) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Sat, 14 Dec 2024 18:47:38 +0800 From: Liu Shixin To: Andrew Morton , Muchun Song , Kenneth W Chen , Kefeng Wang , Nanyong Sun CC: , , Liu Shixin Subject: [PATCH] mm: hugetlb: independent PMD page table shared count Date: Sat, 14 Dec 2024 18:44:01 +0800 Message-ID: <20241214104401.1052550-1-liushixin2@huawei.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemg200013.china.huawei.com (7.202.181.64) Content-Type: text/plain; charset="utf-8" The folio refcount may be increased unexpectly through try_get_folio() by caller such as split_huge_pages. In huge_pmd_unshare(), we use refcount to check whether a pmd page table is shared. The check is incorrect if the refcount is increased by the above caller, and this can cause the page table leaked: BUG: Bad page state in process sh pfn:109324 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x66 pfn:0x1093= 24 flags: 0x17ffff800000000(node=3D0|zone=3D2|lastcpupid=3D0xfffff) page_type: f2(table) raw: 017ffff800000000 0000000000000000 0000000000000000 0000000000000000 raw: 0000000000000066 0000000000000000 00000000f2000000 0000000000000000 page dumped because: nonzero mapcount ... CPU: 31 UID: 0 PID: 7515 Comm: sh Kdump: loaded Tainted: G B = 6.13.0-rc2master+ #7 Tainted: [B]=3DBAD_PAGE Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 Call trace: show_stack+0x20/0x38 (C) dump_stack_lvl+0x80/0xf8 dump_stack+0x18/0x28 bad_page+0x8c/0x130 free_page_is_bad_report+0xa4/0xb0 free_unref_page+0x3cc/0x620 __folio_put+0xf4/0x158 split_huge_pages_all+0x1e0/0x3e8 split_huge_pages_write+0x25c/0x2d8 full_proxy_write+0x64/0xd8 vfs_write+0xcc/0x280 ksys_write+0x70/0x110 __arm64_sys_write+0x24/0x38 invoke_syscall+0x50/0x120 el0_svc_common.constprop.0+0xc8/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x34/0x128 el0t_64_sync_handler+0xc8/0xd0 el0t_64_sync+0x190/0x198 The issue may be triggered by damon, offline_page, page_idle etc. which will increase the refcount of page table. Fix it by introducing independent PMD page table shared count. Fixes: 39dde65c9940 ("[PATCH] shared page table for hugetlb page") Signed-off-by: Liu Shixin --- include/linux/mm.h | 1 + include/linux/mm_types.h | 28 ++++++++++++++++++++++++++++ mm/hugetlb.c | 16 +++++++--------- 3 files changed, 36 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index c39c4945946c..50fbf2a1b0ad 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3115,6 +3115,7 @@ static inline bool pagetable_pmd_ctor(struct ptdesc *= ptdesc) if (!pmd_ptlock_init(ptdesc)) return false; __folio_set_pgtable(folio); + ptdesc_pmd_pts_init(ptdesc); lruvec_stat_add_folio(folio, NR_PAGETABLE); return true; } diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 7361a8f3ab68..740b765ac91e 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -445,6 +445,7 @@ FOLIO_MATCH(compound_head, _head_2a); * @pt_index: Used for s390 gmap. * @pt_mm: Used for x86 pgds. * @pt_frag_refcount: For fragmented page table tracking. Powerpc only. + * @pt_share_count: Used for HugeTLB PMD page table share count. * @_pt_pad_2: Padding to ensure proper alignment. * @ptl: Lock for the page table. * @__page_type: Same as page->page_type. Unused for page tables. @@ -471,6 +472,9 @@ struct ptdesc { pgoff_t pt_index; struct mm_struct *pt_mm; atomic_t pt_frag_refcount; +#ifdef CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING + atomic_t pt_share_count; +#endif }; =20 union { @@ -516,6 +520,30 @@ static_assert(sizeof(struct ptdesc) <=3D sizeof(struct= page)); const struct page *: (const struct ptdesc *)(p), \ struct page *: (struct ptdesc *)(p))) =20 +#ifdef CONFIG_HUGETLB_PMD_PAGE_TABLE_SHARING +static inline void ptdesc_pmd_pts_init(struct ptdesc *ptdesc) +{ + atomic_set(&ptdesc->pt_share_count, 0); +} + +static inline void ptdesc_pmd_pts_inc(struct ptdesc *ptdesc) +{ + atomic_inc(&ptdesc->pt_share_count); +} + +static inline void ptdesc_pmd_pts_dec(struct ptdesc *ptdesc) +{ + atomic_dec(&ptdesc->pt_share_count); +} + +static inline int ptdesc_pmd_pts_count(struct ptdesc *ptdesc) +{ + return atomic_read(&ptdesc->pt_share_count); +} +#else +#define ptdesc_pmd_pts_init NULL +#endif + /* * Used for sizing the vmemmap region on some architectures */ diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ea2ed8e301ef..60846b060b87 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -7212,7 +7212,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm= _area_struct *vma, spte =3D hugetlb_walk(svma, saddr, vma_mmu_pagesize(svma)); if (spte) { - get_page(virt_to_page(spte)); + ptdesc_pmd_pts_inc(virt_to_ptdesc(spte)); break; } } @@ -7227,7 +7227,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct vm= _area_struct *vma, (pmd_t *)((unsigned long)spte & PAGE_MASK)); mm_inc_nr_pmds(mm); } else { - put_page(virt_to_page(spte)); + ptdesc_pmd_pts_dec(virt_to_ptdesc(spte)); } spin_unlock(&mm->page_table_lock); out: @@ -7239,10 +7239,6 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct v= m_area_struct *vma, /* * unmap huge page backed by shared pte. * - * Hugetlb pte page is ref counted at the time of mapping. If pte is shar= ed - * indicated by page_count > 1, unmap is achieved by clearing pud and - * decrementing the ref count. If count =3D=3D 1, the pte page is not shar= ed. - * * Called with page table lock held. * * returns: 1 successfully unmapped a shared pte page @@ -7251,18 +7247,20 @@ pte_t *huge_pmd_share(struct mm_struct *mm, struct = vm_area_struct *vma, int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) { + unsigned long sz =3D huge_page_size(hstate_vma(vma)); pgd_t *pgd =3D pgd_offset(mm, addr); p4d_t *p4d =3D p4d_offset(pgd, addr); pud_t *pud =3D pud_offset(p4d, addr); =20 i_mmap_assert_write_locked(vma->vm_file->f_mapping); hugetlb_vma_assert_locked(vma); - BUG_ON(page_count(virt_to_page(ptep)) =3D=3D 0); - if (page_count(virt_to_page(ptep)) =3D=3D 1) + if (sz !=3D PMD_SIZE) + return 0; + if (!ptdesc_pmd_pts_count(virt_to_ptdesc(ptep))) return 0; =20 pud_clear(pud); - put_page(virt_to_page(ptep)); + ptdesc_pmd_pts_dec(virt_to_ptdesc(ptep)); mm_dec_nr_pmds(mm); return 1; } --=20 2.34.1