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SubjectRe: + mm-proc-pid-smaps_rollup-convert-to-single-value-seq_file.patch added to -mm tree
On Mon, Jul 23, 2018 at 04:55:48PM -0700, akpm@linux-foundation.org wrote:
> The patch titled
> Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file
> has been added to the -mm tree. Its filename is
> mm-proc-pid-smaps_rollup-convert-to-single-value-seq_file.patch

> Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file
>
> The /proc/pid/smaps_rollup file is currently implemented via the
> m_start/m_next/m_stop seq_file iterators shared with the other maps files,
> that iterate over vma's. However, the rollup file doesn't print anything
> for each vma, only accumulate the stats.

What I don't understand why keep seq_ops then and not do all the work in
->show hook. Currently /proc/*/smaps_rollup is at ~500 bytes so with
minimum 1 page seq buffer, no buffer resizing is possible.

> +static int show_smaps_rollup(struct seq_file *m, void *v)
> +{
> + struct proc_maps_private *priv = m->private;
> + struct mem_size_stats *mss = priv->rollup;
> + struct vm_area_struct *vma;
> +
> + /*
> + * We might be called multiple times when e.g. the seq buffer
> + * overflows. Gather the stats only once.

It doesn't!

> + if (!mss->finished) {
> + for (vma = priv->mm->mmap; vma; vma = vma->vm_next) {
> + smap_gather_stats(vma, mss);
> + mss->last_vma_end = vma->vm_end;
> }
> - last_vma = !m_next_vma(priv, vma);
> - } else {
> - rollup_mode = false;
> - memset(&mss_stack, 0, sizeof(mss_stack));
> - mss = &mss_stack;

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