On 10/20/2017 12:10 AM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@xxxxxxxxx>
>
> Now, when the page table is walked in the implementation of
> /proc/<pid>/pagemap, pmd_soft_dirty() is used for both the PMD huge
> page map and the PMD migration entries. That is wrong,
> pmd_swp_soft_dirty() should be used for the PMD migration entries
> instead because the different page table entry flag is used.
> Otherwise, the soft dirty information in /proc/<pid>/pagemap may be
> wrong.
>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
> Cc: Daniel Colascione <dancol@xxxxxxxxxx>
> Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path")
> ---
> fs/proc/task_mmu.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 2593a0c609d7..01aad772f8db 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -1311,13 +1311,15 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
> pmd_t pmd = *pmdp;
> struct page *page = NULL;
>
> - if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(pmd))
> + if (vma->vm_flags & VM_SOFTDIRTY)
> flags |= PM_SOFT_DIRTY;
right, checking bits in pmd must be done after pmd_present is confirmed.
Acked-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Thanks,
Naoya Horiguchi
>
> if (pmd_present(pmd)) {
> page = pmd_page(pmd);
>
> flags |= PM_PRESENT;
> + if (pmd_soft_dirty(pmd))
> + flags |= PM_SOFT_DIRTY;
> if (pm->show_pfn)
> frame = pmd_pfn(pmd) +
> ((addr & ~PMD_MASK) >> PAGE_SHIFT);
> @@ -1329,6 +1331,8 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
> frame = swp_type(entry) |
> (swp_offset(entry) << MAX_SWAPFILES_SHIFT);
> flags |= PM_SWAP;
> + if (pmd_swp_soft_dirty(pmd))
> + flags |= PM_SOFT_DIRTY;
> VM_BUG_ON(!is_pmd_migration_entry(pmd));
> page = migration_entry_to_page(entry);
> }
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