Re: [PATCH v3 2/3] mm: smaps*: extend smap_gather_stats to support specified beginning

Steven Price
2020-08-17T09:08:07Z

On 15/08/2020 07:20, Chinwen Chang wrote:
> Extend smap_gather_stats to support indicated beginning address at
> which it should start gathering. To achieve the goal, we add a new
> parameter @start assigned by the caller and try to refactor it for
> simplicity.
>
> If @start is 0, it will use the range of @vma for gathering.
>
> Change since v2:
> - This is a new change to make the retry behavior of smaps_rollup
> - more complete as suggested by Michel [1]
>
> [1] https://lore.kernel.org/lkml/CANN689FtCsC71cjAjs0GPspOhgo_HRj+diWsoU1wr98YPktgWg@mail.gmail.com/
>
> Signed-off-by: Chinwen Chang <chinwen.chang@mediatek.com>
> CC: Michel Lespinasse <walken@google.com>
> CC: Steven Price <steven.price@arm.com>

LGTM

Reviewed-by: Steven Price <steven.price@arm.com>

Steve

> ---
> fs/proc/task_mmu.c | 30 ++++++++++++++++++++++--------
> 1 file changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index dbda449..76e623a 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -723,9 +723,21 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
> .pte_hole = smaps_pte_hole,
> };
>
> +/*
> + * Gather mem stats from @vma with the indicated beginning
> + * address @start, and keep them in @mss.
> + *
> + * Use vm_start of @vma as the beginning address if @start is 0.
> + */
> static void smap_gather_stats(struct vm_area_struct *vma,
> - struct mem_size_stats *mss)
> + struct mem_size_stats *mss, unsigned long start)
> {
> + const struct mm_walk_ops *ops = &smaps_walk_ops;
> +
> + /* Invalid start */
> + if (start >= vma->vm_end)
> + return;
> +
> #ifdef CONFIG_SHMEM
> /* In case of smaps_rollup, reset the value from previous vma */
> mss->check_shmem_swap = false;
> @@ -742,18 +754,20 @@ static void smap_gather_stats(struct vm_area_struct *vma,
> */
> unsigned long shmem_swapped = shmem_swap_usage(vma);
>
> - if (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
> - !(vma->vm_flags & VM_WRITE)) {
> + if (!start && (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
> + !(vma->vm_flags & VM_WRITE))) {
> mss->swap += shmem_swapped;
> } else {
> mss->check_shmem_swap = true;
> - walk_page_vma(vma, &smaps_shmem_walk_ops, mss);
> - return;
> + ops = &smaps_shmem_walk_ops;
> }
> }
> #endif
> /* mmap_lock is held in m_start */
> - walk_page_vma(vma, &smaps_walk_ops, mss);
> + if (!start)
> + walk_page_vma(vma, ops, mss);
> + else
> + walk_page_range(vma->vm_mm, start, vma->vm_end, ops, mss);
> }
>
> #define SEQ_PUT_DEC(str, val) \
> @@ -805,7 +819,7 @@ static int show_smap(struct seq_file *m, void *v)
>
> memset(&mss, 0, sizeof(mss));
>
> - smap_gather_stats(vma, &mss);
> + smap_gather_stats(vma, &mss, 0);
>
> show_map_vma(m, vma);
>
> @@ -854,7 +868,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
> hold_task_mempolicy(priv);
>
> for (vma = priv->mm->mmap; vma; vma = vma->vm_next) {
> - smap_gather_stats(vma, &mss);
> + smap_gather_stats(vma, &mss, 0);
> last_vma_end = vma->vm_end;
> }
>
>