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Commit b8c20a9b authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

fs/proc/task_mmu.c: reintroduce m->version logic 



Add the "last_addr" optimization back. Like before, every ->show()
method checks !seq_overflow() and sets m->version = vma->vm_start.

However, it also checks that m_next_vma(vma) != NULL, otherwise it
sets m->version = -1 for the lockless "EOF" fast-path in m_start().

m_start() can simply do find_vma() + m_next_vma() if last_addr is
not zero, the code looks clear and simple and this case is clearly
separated from "scan vmas" path.

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 ad2a00e4

fs/proc/task_mmu.c

+21 −0
Original line number Diff line number Diff line
@@ -146,13 +146,24 @@ m_next_vma(struct proc_maps_private *priv, struct vm_area_struct *vma) 
	return vma->vm_next ?: priv->tail_vma;

}



static void m_cache_vma(struct seq_file *m, struct vm_area_struct *vma)

{

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

		m->version = m_next_vma(m->private, vma) ? vma->vm_start : -1UL;

}



static void *m_start(struct seq_file *m, loff_t *ppos)

{

	struct proc_maps_private *priv = m->private;

	unsigned long last_addr = m->version;

	struct mm_struct *mm;

	struct vm_area_struct *vma;

	unsigned int pos = *ppos;



	/* See m_cache_vma(). Zero at the start or after lseek. */

	if (last_addr == -1UL)

		return NULL;



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

	if (!priv->task)

		return ERR_PTR(-ESRCH);
@@ -165,6 +176,13 @@ static void *m_start(struct seq_file *m, loff_t *ppos) 
	hold_task_mempolicy(priv);

	priv->tail_vma = get_gate_vma(mm);



	if (last_addr) {

		vma = find_vma(mm, last_addr);

		if (vma && (vma = m_next_vma(priv, vma)))

			return vma;

	}



	m->version = 0;

	if (pos < mm->map_count) {

		for (vma = mm->mmap; pos; pos--)

			vma = vma->vm_next;
@@ -340,6 +358,7 @@ 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)

{

	show_map_vma(m, v, is_pid);

	m_cache_vma(m, v);

	return 0;

}
@@ -617,6 +636,7 @@ static int show_smap(struct seq_file *m, void *v, int is_pid) 
				mss.nonlinear >> 10);



	show_smap_vma_flags(m, vma);

	m_cache_vma(m, vma);

	return 0;

}
@@ -1471,6 +1491,7 @@ 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');

	m_cache_vma(m, vma);

	return 0;

}