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fs/proc/task_mmu.c: simplify the vma_stop() logic 

m_start() drops ->mmap_sem and does mmput() if it retuns vsyscall
vma. This is because in this case m_stop()->vma_stop() obviously
can't use gate_vma->vm_mm.

Now that we have proc_maps_private->mm we can simplify this logic:

  - Change m_start() to return with ->mmap_sem held unless it returns
    IS_ERR_OR_NULL().

  - Change vma_stop() to use priv->mm and avoid the ugly vma checks,
    this makes "vm_area_struct *vma" unnecessary.

  - This also allows m_start() to use vm_stop().

  - Cleanup m_next() to follow the new locking rule.

    Note: m_stop() looks very ugly, and this temporary uglifies it
    even more. Fixed by the next change.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: 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 15:25:28 -07:00 committed by Linus Torvalds
parent 29a40ace84
commit 59b4bf12d4
1 changed files with 19 additions and 16 deletions
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35
fs/proc/task_mmu.c
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@ -129,14 +129,13 @@ static void release_task_mempolicy(struct proc_maps_private *priv)
}
#endif
static void vma_stop(struct proc_maps_private *priv, struct vm_area_struct *vma)
static void vma_stop(struct proc_maps_private *priv)
{
if (vma && vma != priv->tail_vma) {
struct mm_struct *mm = vma->vm_mm;
release_task_mempolicy(priv);
up_read(&mm->mmap_sem);
mmput(mm);
}
struct mm_struct *mm = priv->mm;
release_task_mempolicy(priv);
up_read(&mm->mmap_sem);
mmput(mm);
}
static void *m_start(struct seq_file *m, loff_t *pos)
@ -199,12 +198,13 @@ static void *m_start(struct seq_file *m, loff_t *pos)
if (vma)
return vma;
release_task_mempolicy(priv);
/* End of vmas has been reached */
m->version = (tail_vma != NULL)? 0: -1UL;
up_read(&mm->mmap_sem);
mmput(mm);
return tail_vma;
if (tail_vma)
return tail_vma;
vma_stop(priv);
return NULL;
}
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
@ -212,21 +212,24 @@ static void *m_next(struct seq_file *m, void *v, loff_t *pos)
struct proc_maps_private *priv = m->private;
struct vm_area_struct *vma = v;
struct vm_area_struct *tail_vma = priv->tail_vma;
struct vm_area_struct *next;
(*pos)++;
if (vma && (vma != tail_vma) && vma->vm_next)
return vma->vm_next;
vma_stop(priv, vma);
return (vma != tail_vma)? tail_vma: NULL;
next = (vma != tail_vma) ? tail_vma : NULL;
if (!next)
vma_stop(priv);
return next;
}
static void m_stop(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
struct vm_area_struct *vma = v;
if (!IS_ERR(vma))
vma_stop(priv, vma);
if (!IS_ERR_OR_NULL(v))
vma_stop(priv);
if (priv->task)
put_task_struct(priv->task);
}