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.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
fs/proc/task_mmu.c | 34 ++++++++++++++++++----------------
1 files changed, 18 insertions(+), 16 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7ec8eb5..f1254b4 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -129,14 +129,12 @@ 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 +197,13 @@ out:
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 +211,24 @@ 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);
}
--
1.5.5.1
--
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