From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757563Ab3FTJyn (ORCPT ); Thu, 20 Jun 2013 05:54:43 -0400 Received: from mail-pb0-f44.google.com ([209.85.160.44]:56314 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751695Ab3FTJyl (ORCPT ); Thu, 20 Jun 2013 05:54:41 -0400 Date: Thu, 20 Jun 2013 18:52:43 +0900 Message-ID: <87a9ml3y8k.wl%satoru.takeuchi@gmail.com> From: Satoru Takeuchi To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , stable@vger.kernel.org, Naoya Horiguchi , Rik van Riel , Wanpeng Li , Michal Hocko , Mel Gorman , Andi Kleen , KOSAKI Motohiro , Andrew Morton , Linus Torvalds Subject: Re: [ 29/48] mm: migration: add migrate_entry_wait_huge() In-Reply-To: <20130618161730.095209184@linuxfoundation.org> References: <20130618161725.912524266@linuxfoundation.org> <20130618161730.095209184@linuxfoundation.org> User-Agent: Wanderlust/2.14.0 (Africa) Emacs/23.4 Mule/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Naoya, At Tue, 18 Jun 2013 09:17:55 -0700, Greg Kroah-Hartman wrote: > > From: Greg Kroah-Hartman > > 3.9-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Naoya Horiguchi > > commit 30dad30922ccc733cfdbfe232090cf674dc374dc upstream. > > When we have a page fault for the address which is backed by a hugepage > under migration, the kernel can't wait correctly and do busy looping on > hugepage fault until the migration finishes. As a result, users who try > to kick hugepage migration (via soft offlining, for example) occasionally > experience long delay or soft lockup. > > This is because pte_offset_map_lock() can't get a correct migration entry > or a correct page table lock for hugepage. This patch introduces > migration_entry_wait_huge() to solve this. I suspect that this code doesn't work correctly on i686 box with CONFIG_HIGHPTE. If we call hugetlb_fault() -> migration_entry_wait_huge() -> __migration_entry_wait(), this function tries to kunmap pte, in this case pte is not-kmapped pmd, via pte_unmap_unlock(). If CONFIG_DEBUG_HIGHMEM is also enabled, it results in BUG_ON() at __kunmap_atomic(). Correct me if I'm wrong. Thanks, Satoru > > Signed-off-by: Naoya Horiguchi > Reviewed-by: Rik van Riel > Reviewed-by: Wanpeng Li > Reviewed-by: Michal Hocko > Cc: Mel Gorman > Cc: Andi Kleen > Cc: KOSAKI Motohiro > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > Signed-off-by: Greg Kroah-Hartman > > --- > include/linux/swapops.h | 3 +++ > mm/hugetlb.c | 2 +- > mm/migrate.c | 23 ++++++++++++++++++----- > 3 files changed, 22 insertions(+), 6 deletions(-) > > --- a/include/linux/swapops.h > +++ b/include/linux/swapops.h > @@ -137,6 +137,7 @@ static inline void make_migration_entry_ > > extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, > unsigned long address); > +extern void migration_entry_wait_huge(struct mm_struct *mm, pte_t *pte); > #else > > #define make_migration_entry(page, write) swp_entry(0, 0) > @@ -148,6 +149,8 @@ static inline int is_migration_entry(swp > static inline void make_migration_entry_read(swp_entry_t *entryp) { } > static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, > unsigned long address) { } > +static inline void migration_entry_wait_huge(struct mm_struct *mm, > + pte_t *pte) { } > static inline int is_write_migration_entry(swp_entry_t entry) > { > return 0; > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2823,7 +2823,7 @@ int hugetlb_fault(struct mm_struct *mm, > if (ptep) { > entry = huge_ptep_get(ptep); > if (unlikely(is_hugetlb_entry_migration(entry))) { > - migration_entry_wait(mm, (pmd_t *)ptep, address); > + migration_entry_wait_huge(mm, ptep); > return 0; > } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry))) > return VM_FAULT_HWPOISON_LARGE | > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -200,15 +200,14 @@ static void remove_migration_ptes(struct > * get to the page and wait until migration is finished. > * When we return from this function the fault will be retried. > */ > -void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, > - unsigned long address) > +static void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep, > + spinlock_t *ptl) > { > - pte_t *ptep, pte; > - spinlock_t *ptl; > + pte_t pte; > swp_entry_t entry; > struct page *page; > > - ptep = pte_offset_map_lock(mm, pmd, address, &ptl); > + spin_lock(ptl); > pte = *ptep; > if (!is_swap_pte(pte)) > goto out; > @@ -236,6 +235,20 @@ out: > pte_unmap_unlock(ptep, ptl); > } > > +void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, > + unsigned long address) > +{ > + spinlock_t *ptl = pte_lockptr(mm, pmd); > + pte_t *ptep = pte_offset_map(pmd, address); > + __migration_entry_wait(mm, ptep, ptl); > +} > + > +void migration_entry_wait_huge(struct mm_struct *mm, pte_t *pte) > +{ > + spinlock_t *ptl = &(mm)->page_table_lock; > + __migration_entry_wait(mm, pte, ptl); > +} > + > #ifdef CONFIG_BLOCK > /* Returns true if all buffers are successfully locked */ > static bool buffer_migrate_lock_buffers(struct buffer_head *head, > > > -- > To unsubscribe from this list: send the line "unsubscribe stable" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html