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Commit ebb6cdde authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

fs/proc/task_mmu.c: kill the suboptimal and confusing m->version logic 



m_start() carefully documents, checks, and sets "m->version = -1" if
we are going to return NULL. The only problem is that we will be never
called again if m_start() returns NULL, so this is simply pointless
and misleading.

Otoh, ->show() methods m->version = 0 if vma == tail_vma and this is
just wrong, we want -1 in this case. And in fact we also want -1 if
->vm_next == NULL and ->tail_vma == NULL.

And it is not used consistently, the "scan vmas" loop in m_start()
should update last_addr too.

Finally, imo the whole "last_addr" logic in m_start() looks horrible.
find_vma(last_addr) is called unconditionally even if we are not going
to use the result. But the main problem is that this code participates
in tail_vma-or-NULL mess, and this looks simply unfixable.

Remove this optimization. We will add it back after some cleanups.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0d5f5f45

fs/proc/task_mmu.c

+1 −34
Original line number Diff line number Diff line
@@ -141,20 +141,10 @@ static void vma_stop(struct proc_maps_private *priv) 
static void *m_start(struct seq_file *m, loff_t *pos)

{

	struct proc_maps_private *priv = m->private;

	unsigned long last_addr = m->version;

	struct mm_struct *mm;

	struct vm_area_struct *vma, *tail_vma = NULL;

	loff_t l = *pos;



	/*

	 * We remember last_addr rather than next_addr to hit with

	 * vmacache most of the time. We have zero last_addr at

	 * the beginning and also after lseek. We will have -1 last_addr

	 * after the end of the vmas.

	 */

	if (last_addr == -1UL)

		return NULL;



	priv->task = get_pid_task(priv->pid, PIDTYPE_PID);

	if (!priv->task)

		return ERR_PTR(-ESRCH);
@@ -167,12 +157,6 @@ static void *m_start(struct seq_file *m, loff_t *pos) 
	tail_vma = get_gate_vma(mm);

	priv->tail_vma = tail_vma;

	hold_task_mempolicy(priv);

	/* Start with last addr hint */

	vma = find_vma(mm, last_addr);

	if (last_addr && vma) {

		vma = vma->vm_next;

		goto out;

	}



	/*

	 * Check the vma index is within the range and do
@@ -193,8 +177,6 @@ static void *m_start(struct seq_file *m, loff_t *pos) 
	if (vma)

		return vma;



	/* End of vmas has been reached */

	m->version = (tail_vma != NULL)? 0: -1UL;

	if (tail_vma)

		return tail_vma;
@@ -366,14 +348,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid) 


static int show_map(struct seq_file *m, void *v, int is_pid)

{

	struct vm_area_struct *vma = v;

	struct proc_maps_private *priv = m->private;



	show_map_vma(m, vma, is_pid);



	if (m->count < m->size)  /* vma is copied successfully */

		m->version = (vma != priv->tail_vma)

			? vma->vm_start : 0;

	show_map_vma(m, v, is_pid);

	return 0;

}
@@ -599,7 +574,6 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) 


static int show_smap(struct seq_file *m, void *v, int is_pid)

{

	struct proc_maps_private *priv = m->private;

	struct vm_area_struct *vma = v;

	struct mem_size_stats mss;

	struct mm_walk smaps_walk = {
@@ -652,10 +626,6 @@ static int show_smap(struct seq_file *m, void *v, int is_pid) 
				mss.nonlinear >> 10);



	show_smap_vma_flags(m, vma);



	if (m->count < m->size)  /* vma is copied successfully */

		m->version = (vma != priv->tail_vma)

			? vma->vm_start : 0;

	return 0;

}
@@ -1510,9 +1480,6 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid) 
			seq_printf(m, " N%d=%lu", nid, md->node[nid]);

out:

	seq_putc(m, '\n');



	if (m->count < m->size)

		m->version = (vma != proc_priv->tail_vma) ? vma->vm_start : 0;

	return 0;

}