From 0c255321f879c36bd74f58f9c7ed235ea6b919cb Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 9 Oct 2014 15:25:36 -0700 Subject: [PATCH] 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 Cc: Kirill A. Shutemov Cc: Cyrill Gorcunov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 34 ++++++++++------------------------ 1 file changed, 10 insertions(+), 24 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index e182fc51ec2b..bb16c967eefd 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -138,12 +138,12 @@ static void vma_stop(struct proc_maps_private *priv) 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 @@ static void *m_start(struct seq_file *m, loff_t *pos) 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; + down_read(&mm->mmap_sem); 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; - } - - 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; -- 2.20.1