fs/proc/task_mmu.c: simplify the vma_stop() logic (59b4bf12) · Commits · 戴 / test

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>

fs/proc/task_mmu.c

+19 −16

Original line number	Diff line number	Diff line
		@@ -129,15 +129,14 @@ 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;
		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);
		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);
		}

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