Re: [PATCH v5 1/3] mm, proc: Implement /proc/<pid>/totmaps

From: Robert Foss
Date: Mon Sep 12 2016 - 18:12:43 EST


Hey Oleg!

Thanks for the feedback, I'll keep it in mind, but currently it looks like the patch is on ice for non-implementation related reasons.


Rob.


@@ -2854,6 +2854,7 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
REG("smaps", S_IRUGO, proc_pid_smaps_operations),
REG("pagemap", S_IRUSR, proc_pagemap_operations),
+ REG("totmaps", S_IRUGO, proc_totmaps_operations),

I must have missed something, but I fail to understand why this patch
is so complicated.

Just use ONE("totmaps", S_IRUGO, proc_totmaps_operations) ?

+static int totmaps_proc_show(struct seq_file *m, void *data)
+{
+ struct proc_maps_private *priv = m->private;
+ struct mm_struct *mm = priv->mm;
+ struct vm_area_struct *vma;
+ struct mem_size_stats mss_sum;
+
+ memset(&mss_sum, 0, sizeof(mss_sum));
+ down_read(&mm->mmap_sem);
+ hold_task_mempolicy(priv);
^^^^^^^^^^^^^^^^^^^^^^^^^
why?

+ for (vma = mm->mmap; vma != priv->tail_vma; vma = vma->vm_next) {

Hmm. the usage of ->tail_vma looks just wrong. I guess the code should
work because it is NULL but still.

+ struct mem_size_stats mss;
+ struct mm_walk smaps_walk = {
+ .pmd_entry = smaps_pte_range,
+ .mm = vma->vm_mm,
+ .private = &mss,
+ };
+
+ if (vma->vm_mm && !is_vm_hugetlb_page(vma)) {
+ memset(&mss, 0, sizeof(mss));
+ walk_page_vma(vma, &smaps_walk);
+ add_smaps_sum(&mss, &mss_sum);
+ }
+ }

Why? I mean, why not walk_page_range() ? You do not need this for-each-vma
loop at all? At least if you change this patch to use the ONE() helper, and
everything else looks unneeded in this case.

Oleg.