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    SubjectRe: [PATCH v3 2/2] migrate: add migrate_entry_wait_huge()
    On Mon, Jun 03, 2013 at 03:26:41PM +0200, Michal Hocko wrote:
    > On Tue 28-05-13 15:52:51, 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 and do busy looping on
    > > hugepage fault until the migration finishes.
    > > 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.
    > >
    > > Note that the caller, hugetlb_fault(), gets the pointer to the "leaf"
    > > entry with huge_pte_offset() inside which all the arch-dependency of
    > > the page table structure are. So migration_entry_wait_huge() and
    > > __migration_entry_wait() are free from arch-dependency.
    > >
    > > ChangeLog v3:
    > > - use huge_pte_lockptr
    > >
    > > ChangeLog v2:
    > > - remove dup in migrate_entry_wait_huge()
    > >
    > > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    > > Reviewed-by: Rik van Riel <riel@redhat.com>
    > > Cc: stable@vger.kernel.org # 2.6.35
    >
    > OK, this looks good to me and I guess you can safely replace
    > huge_pte_lockptr by &(mm)->page_table_lock so you can implement this
    > even without risky 1/2 of this series. The patch should be as simple as
    > possible especially when it goes to the stable.

    Yes, I agree.

    > > Without 1/2 dependency
    > Reviewed-by: Michal Hocko <mhocko@suse.cz>

    Thanks,
    Naoya


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