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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: Oleg 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2014-10-09 15:25:41 -07:00 committed by Linus Torvalds
parent ad2a00e4b7
commit b8c20a9b85
1 changed files with 21 additions and 0 deletions
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21
fs/proc/task_mmu.c
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@ -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 @@ done:
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;
}