From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CAC47C433F5 for ; Wed, 9 Mar 2022 08:48:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 635C88D0022; Wed, 9 Mar 2022 03:48:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5BE7C8D0001; Wed, 9 Mar 2022 03:48:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 438748D0022; Wed, 9 Mar 2022 03:48:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0169.hostedemail.com [216.40.44.169]) by kanga.kvack.org (Postfix) with ESMTP id 2D3188D0001 for ; Wed, 9 Mar 2022 03:48:45 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id C90DC8249980 for ; Wed, 9 Mar 2022 08:48:44 +0000 (UTC) X-FDA: 79224222168.28.600DF85 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf14.hostedemail.com (Postfix) with ESMTP id A11AA100014 for ; Wed, 9 Mar 2022 08:48:43 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KD5MX00yyz1GCG9; Wed, 9 Mar 2022 16:43:51 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Wed, 9 Mar 2022 16:48:39 +0800 Subject: Re: [PATCH 16/16] mm/migration: fix potential pte_unmap on an not mapped pte To: "Huang, Ying" CC: , , , , , , , , , , , , , , , , References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-17-linmiaohe@huawei.com> <871qze5nmv.fsf@yhuang6-desk2.ccr.corp.intel.com> <9c6873ae-7614-1178-8c9f-6e933a12e35b@huawei.com> <877d94gczc.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Miaohe Lin Message-ID: <56baf172-4a0f-676e-86ef-61e2fef87520@huawei.com> Date: Wed, 9 Mar 2022 16:48:39 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <877d94gczc.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: A11AA100014 X-Stat-Signature: chu5htbjz6pqddajkj4s33tu9tfpo1oa Authentication-Results: imf14.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf14.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspam-User: X-HE-Tag: 1646815723-588456 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/3/9 8:56, Huang, Ying wrote: > Miaohe Lin writes: > >> On 2022/3/7 13:37, Huang, Ying wrote: >>> Miaohe Lin writes: >>> >>>> __migration_entry_wait and migration_entry_wait_on_locked assume pte is >>>> always mapped from caller. But this is not the case when it's called from >>>> migration_entry_wait_huge and follow_huge_pmd. And a parameter unmap to >>>> indicate whether pte needs to be unmapped to fix this issue. >>> >>> This seems a possible issue. >>> >>> Have you tested it? It appears that it's possible to trigger the >>> issue. If so, you can paste the error log here. >> >> This might happen iff on x86 machine with HIGHMEM enabled which is uncommon >> now (at least in my work environment). > > Yes. 32-bit isn't popular now. But you can always test it via virtual > machine. > Good idea. >> So I can't paste the err log. And The >> issues from this series mainly come from the code investigating with some tests. > > If not too complex, I still think it's better to test your code and > verify the problem. Sure! :) Many thanks. > > Best Regards, > Huang, Ying > >> Thanks. :) >> >>> >>> BTW: have you tested the other functionality issues in your patchset? >>> >>> Best Regards, >>> Huang, Ying >>> >>>> Fixes: 30dad30922cc ("mm: migration: add migrate_entry_wait_huge()") >>>> Signed-off-by: Miaohe Lin >>>> --- >>>> include/linux/migrate.h | 2 +- >>>> include/linux/swapops.h | 4 ++-- >>>> mm/filemap.c | 10 +++++----- >>>> mm/hugetlb.c | 2 +- >>>> mm/migrate.c | 14 ++++++++------ >>>> 5 files changed, 17 insertions(+), 15 deletions(-) >>>> >>>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h >>>> index 66a34eae8cb6..3ef4ff699bef 100644 >>>> --- a/include/linux/migrate.h >>>> +++ b/include/linux/migrate.h >>>> @@ -41,7 +41,7 @@ extern int migrate_huge_page_move_mapping(struct address_space *mapping, >>>> extern int migrate_page_move_mapping(struct address_space *mapping, >>>> struct page *newpage, struct page *page, int extra_count); >>>> void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep, >>>> - spinlock_t *ptl); >>>> + spinlock_t *ptl, bool unmap); >>>> void folio_migrate_flags(struct folio *newfolio, struct folio *folio); >>>> void folio_migrate_copy(struct folio *newfolio, struct folio *folio); >>>> int folio_migrate_mapping(struct address_space *mapping, >>>> diff --git a/include/linux/swapops.h b/include/linux/swapops.h >>>> index d356ab4047f7..d66556875d7d 100644 >>>> --- a/include/linux/swapops.h >>>> +++ b/include/linux/swapops.h >>>> @@ -213,7 +213,7 @@ static inline swp_entry_t make_writable_migration_entry(pgoff_t offset) >>>> } >>>> >>>> extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, >>>> - spinlock_t *ptl); >>>> + spinlock_t *ptl, bool unmap); >>>> extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, >>>> unsigned long address); >>>> extern void migration_entry_wait_huge(struct vm_area_struct *vma, >>>> @@ -235,7 +235,7 @@ static inline int is_migration_entry(swp_entry_t swp) >>>> } >>>> >>>> static inline void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, >>>> - spinlock_t *ptl) { } >>>> + spinlock_t *ptl, bool unmap) { } >>>> static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, >>>> unsigned long address) { } >>>> static inline void migration_entry_wait_huge(struct vm_area_struct *vma, >>>> diff --git a/mm/filemap.c b/mm/filemap.c >>>> index 8f7e6088ee2a..18c353d52aae 100644 >>>> --- a/mm/filemap.c >>>> +++ b/mm/filemap.c >>>> @@ -1389,6 +1389,7 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr, >>>> * @ptep: mapped pte pointer. Will return with the ptep unmapped. Only required >>>> * for pte entries, pass NULL for pmd entries. >>>> * @ptl: already locked ptl. This function will drop the lock. >>>> + * @unmap: indicating whether ptep need to be unmapped. >>>> * >>>> * Wait for a migration entry referencing the given page to be removed. This is >>>> * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except >>>> @@ -1402,7 +1403,7 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr, >>>> * there. >>>> */ >>>> void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep, >>>> - spinlock_t *ptl) >>>> + spinlock_t *ptl, bool unmap) >>>> { >>>> struct wait_page_queue wait_page; >>>> wait_queue_entry_t *wait = &wait_page.wait; >>>> @@ -1439,10 +1440,9 @@ void migration_entry_wait_on_locked(swp_entry_t entry, pte_t *ptep, >>>> * a valid reference to the page, and it must take the ptl to remove the >>>> * migration entry. So the page is valid until the ptl is dropped. >>>> */ >>>> - if (ptep) >>>> - pte_unmap_unlock(ptep, ptl); >>>> - else >>>> - spin_unlock(ptl); >>>> + spin_unlock(ptl); >>>> + if (unmap && ptep) >>>> + pte_unmap(ptep); >>>> >>>> for (;;) { >>>> unsigned int flags; >>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>> index 07668781c246..8088128c25db 100644 >>>> --- a/mm/hugetlb.c >>>> +++ b/mm/hugetlb.c >>>> @@ -6713,7 +6713,7 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address, >>>> } else { >>>> if (is_hugetlb_entry_migration(pte)) { >>>> spin_unlock(ptl); >>>> - __migration_entry_wait(mm, (pte_t *)pmd, ptl); >>>> + __migration_entry_wait(mm, (pte_t *)pmd, ptl, false); >>>> goto retry; >>>> } >>>> /* >>>> diff --git a/mm/migrate.c b/mm/migrate.c >>>> index 98a968e6f465..5519261f54fe 100644 >>>> --- a/mm/migrate.c >>>> +++ b/mm/migrate.c >>>> @@ -281,7 +281,7 @@ void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked) >>>> * When we return from this function the fault will be retried. >>>> */ >>>> void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, >>>> - spinlock_t *ptl) >>>> + spinlock_t *ptl, bool unmap) >>>> { >>>> pte_t pte; >>>> swp_entry_t entry; >>>> @@ -295,10 +295,12 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, >>>> if (!is_migration_entry(entry)) >>>> goto out; >>>> >>>> - migration_entry_wait_on_locked(entry, ptep, ptl); >>>> + migration_entry_wait_on_locked(entry, ptep, ptl, unmap); >>>> return; >>>> out: >>>> - pte_unmap_unlock(ptep, ptl); >>>> + spin_unlock(ptl); >>>> + if (unmap) >>>> + pte_unmap(ptep); >>>> } >>>> >>>> void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, >>>> @@ -306,14 +308,14 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, >>>> { >>>> spinlock_t *ptl = pte_lockptr(mm, pmd); >>>> pte_t *ptep = pte_offset_map(pmd, address); >>>> - __migration_entry_wait(mm, ptep, ptl); >>>> + __migration_entry_wait(mm, ptep, ptl, true); >>>> } >>>> >>>> void migration_entry_wait_huge(struct vm_area_struct *vma, >>>> struct mm_struct *mm, pte_t *pte) >>>> { >>>> spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte); >>>> - __migration_entry_wait(mm, pte, ptl); >>>> + __migration_entry_wait(mm, pte, ptl, false); >>>> } >>>> >>>> #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION >>>> @@ -324,7 +326,7 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd) >>>> ptl = pmd_lock(mm, pmd); >>>> if (!is_pmd_migration_entry(*pmd)) >>>> goto unlock; >>>> - migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), NULL, ptl); >>>> + migration_entry_wait_on_locked(pmd_to_swp_entry(*pmd), NULL, ptl, false); >>>> return; >>>> unlock: >>>> spin_unlock(ptl); >>> . >>> > . >