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Message-ID: <5148FB6C.4070202@gmail.com>
Date: Wed, 20 Mar 2013 07:57:32 +0800
From: Simon Jeons <simon.jeons@...il.com>
To: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
CC: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/9] migrate: add migrate_entry_wait_huge()
Hi Naoya,
On 02/22/2013 03:41 AM, Naoya Horiguchi wrote:
> When we have a page fault for the address which is backed by a hugepage
> under migration, the kernel can't wait correctly until the migration
> finishes. This is because pte_offset_map_lock() can't get a correct
It seems that current hugetlb_fault still wait hugetlb page under
migration, how can it work without lock 2MB memory?
> migration entry for hugepage. This patch adds migration_entry_wait_huge()
> to separate code path between normal pages and hugepages.
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> ---
> include/linux/hugetlb.h | 2 ++
> include/linux/swapops.h | 4 ++++
> mm/hugetlb.c | 4 ++--
> mm/migrate.c | 24 ++++++++++++++++++++++++
> 4 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git v3.8.orig/include/linux/hugetlb.h v3.8/include/linux/hugetlb.h
> index 0c80d3f..40b27f6 100644
> --- v3.8.orig/include/linux/hugetlb.h
> +++ v3.8/include/linux/hugetlb.h
> @@ -43,6 +43,7 @@ int hugetlb_mempolicy_sysctl_handler(struct ctl_table *, int,
> #endif
>
> int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *);
> +int is_hugetlb_entry_migration(pte_t pte);
> int follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *,
> struct page **, struct vm_area_struct **,
> unsigned long *, int *, int, unsigned int flags);
> @@ -109,6 +110,7 @@ static inline unsigned long hugetlb_total_pages(void)
> #define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; })
> #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL)
> #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; })
> +#define is_hugetlb_entry_migration(pte) ({ BUG(); 0; })
> #define hugetlb_prefault(mapping, vma) ({ BUG(); 0; })
> static inline void hugetlb_report_meminfo(struct seq_file *m)
> {
> diff --git v3.8.orig/include/linux/swapops.h v3.8/include/linux/swapops.h
> index 47ead51..f68efdd 100644
> --- v3.8.orig/include/linux/swapops.h
> +++ v3.8/include/linux/swapops.h
> @@ -137,6 +137,8 @@ static inline void make_migration_entry_read(swp_entry_t *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, pmd_t *pmd,
> + unsigned long address);
> #else
>
> #define make_migration_entry(page, write) swp_entry(0, 0)
> @@ -148,6 +150,8 @@ static inline int is_migration_entry(swp_entry_t 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, pmd_t *pmd,
> + unsigned long address) { }
> static inline int is_write_migration_entry(swp_entry_t entry)
> {
> return 0;
> diff --git v3.8.orig/mm/hugetlb.c v3.8/mm/hugetlb.c
> index 546db81..351025e 100644
> --- v3.8.orig/mm/hugetlb.c
> +++ v3.8/mm/hugetlb.c
> @@ -2313,7 +2313,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
> return -ENOMEM;
> }
>
> -static int is_hugetlb_entry_migration(pte_t pte)
> +int is_hugetlb_entry_migration(pte_t pte)
> {
> swp_entry_t swp;
>
> @@ -2823,7 +2823,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> 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, (pmd_t *)ptep, address);
> return 0;
> } else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))
> return VM_FAULT_HWPOISON_LARGE |
> diff --git v3.8.orig/mm/migrate.c v3.8/mm/migrate.c
> index 2fd8b4a..7d84f4c 100644
> --- v3.8.orig/mm/migrate.c
> +++ v3.8/mm/migrate.c
> @@ -236,6 +236,30 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
> pte_unmap_unlock(ptep, ptl);
> }
>
> +void migration_entry_wait_huge(struct mm_struct *mm, pmd_t *pmd,
> + unsigned long address)
> +{
> + spinlock_t *ptl = pte_lockptr(mm, pmd);
> + pte_t pte;
> + swp_entry_t entry;
> + struct page *page;
> +
> + spin_lock(ptl);
> + pte = huge_ptep_get((pte_t *)pmd);
> + if (!is_hugetlb_entry_migration(pte))
> + goto out;
> + entry = pte_to_swp_entry(pte);
> + page = migration_entry_to_page(entry);
> + if (!get_page_unless_zero(page))
> + goto out;
> + spin_unlock(ptl);
> + wait_on_page_locked(page);
> + put_page(page);
> + return;
> +out:
> + spin_unlock(ptl);
> +}
> +
> #ifdef CONFIG_BLOCK
> /* Returns true if all buffers are successfully locked */
> static bool buffer_migrate_lock_buffers(struct buffer_head *head,
--
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