Peter Xu <peterx@xxxxxxxxxx> writes:
> These bits should only be valid when the ptes are present. Introducing two
> booleans for it and set it to false when !pte_present() for both pte and
> pmd accountings.
>
> The bug is found during code reading and no real world issue reported, but
> logically such an error can cause incorrect readings for either smaps or
> smaps_rollup output on quite a few fields.
>
> For example, it could cause over-estimate on values like Shared_Dirty,
> Private_Dirty, Referenced. Or it could also cause under-estimate on values
> like LazyFree, Shared_Clean, Private_Clean.
>
> Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Fixes: b1d4d9e0cbd0 ("proc/smaps: carefully handle migration entries")
> Fixes: c94b6923fa0a ("/proc/PID/smaps: Add PMD migration entry parsing")
> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
LGTM, Thanks!
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
> ---
> fs/proc/task_mmu.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 9913f3be9fd2..d56c65f98d00 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> struct vm_area_struct *vma = walk->vma;
> bool locked = !!(vma->vm_flags & VM_LOCKED);
> struct page *page = NULL;
> - bool migration = false;
> + bool migration = false, young = false, dirty = false;
>
> if (pte_present(*pte)) {
> page = vm_normal_page(vma, addr, *pte);
> + young = pte_young(*pte);
> + dirty = pte_dirty(*pte);
> } else if (is_swap_pte(*pte)) {
> swp_entry_t swpent = pte_to_swp_entry(*pte);
>
> @@ -560,8 +562,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> if (!page)
> return;
>
> - smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte),
> - locked, migration);
> + smaps_account(mss, page, false, young, dirty, locked, migration);
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> @@ -572,11 +573,13 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
> struct vm_area_struct *vma = walk->vma;
> bool locked = !!(vma->vm_flags & VM_LOCKED);
> struct page *page = NULL;
> - bool migration = false;
> + bool migration = false, young = false, dirty = false;
>
> if (pmd_present(*pmd)) {
> /* FOLL_DUMP will return -EFAULT on huge zero page */
> page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);
> + young = pmd_young(*pmd);
> + dirty = pmd_dirty(*pmd);
> } else if (unlikely(thp_migration_supported() && is_swap_pmd(*pmd))) {
> swp_entry_t entry = pmd_to_swp_entry(*pmd);
>
> @@ -596,8 +599,7 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
> else
> mss->file_thp += HPAGE_PMD_SIZE;
>
> - smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd),
> - locked, migration);
> + smaps_account(mss, page, true, young, dirty, locked, migration);
> }
> #else
> static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
