fs/proc/task_mmu.c: simplify m_start() to make it readable
Now that m->version is gone we can cleanup m_start(). In particular,
- Remove the "unsigned long" typecast, m->index can't be negative
or exceed ->map_count. But lets use "unsigned int pos" to make
it clear that "pos < map_count" is safe.
- Remove the unnecessary "vma != NULL" check in the main loop. It
can't be NULL unless we have a vm bug.
- This also means that "pos < map_count" case can simply return the
valid vma and avoid "goto" and subsequent checks.
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>
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e182fc5..bb16c96 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -138,12 +138,12 @@
mmput(mm);
}
-static void *m_start(struct seq_file *m, loff_t *pos)
+static void *m_start(struct seq_file *m, loff_t *ppos)
{
struct proc_maps_private *priv = m->private;
struct mm_struct *mm;
- struct vm_area_struct *vma, *tail_vma = NULL;
- loff_t l = *pos;
+ struct vm_area_struct *vma;
+ unsigned int pos = *ppos;
priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
if (!priv->task)
@@ -152,33 +152,19 @@
mm = priv->mm;
if (!mm || !atomic_inc_not_zero(&mm->mm_users))
return NULL;
+
down_read(&mm->mmap_sem);
-
- tail_vma = get_gate_vma(mm);
- priv->tail_vma = tail_vma;
hold_task_mempolicy(priv);
+ priv->tail_vma = get_gate_vma(mm);
- /*
- * Check the vma index is within the range and do
- * sequential scan until m_index.
- */
- vma = NULL;
- if ((unsigned long)l < mm->map_count) {
- vma = mm->mmap;
- while (l-- && vma)
+ if (pos < mm->map_count) {
+ for (vma = mm->mmap; pos; pos--)
vma = vma->vm_next;
- goto out;
+ return vma;
}
- if (l != mm->map_count)
- tail_vma = NULL; /* After gate vma */
-
-out:
- if (vma)
- return vma;
-
- if (tail_vma)
- return tail_vma;
+ if (pos == mm->map_count && priv->tail_vma)
+ return priv->tail_vma;
vma_stop(priv);
return NULL;