From 59b4bf12d4776c0e4f3fd5c02d942f3a0596da97 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 9 Oct 2014 15:25:28 -0700 Subject: [PATCH] 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 Acked-by: Kirill A. Shutemov Acked-by: Cyrill Gorcunov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index a1454dac7e0a..fdbed8370db6 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -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 @@ 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 +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); } -- 2.20.1