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

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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: 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 15:25:34 -07:00 committed by Linus Torvalds
parent 0d5f5f45f9
commit ebb6cdde1a
1 changed files with 1 additions and 34 deletions
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35
fs/proc/task_mmu.c
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@ -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 @@ out:
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 @@ done:
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;
}