From ebb6cdde1a50c3cd2a0a4668dfb571ecb3213449 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 9 Oct 2014 15:25:34 -0700 Subject: [PATCH] fs/proc/task_mmu.c: kill the suboptimal and confusing m->version logic m_start() carefully documents, checks, and sets "m->version = -1" if we are going to return NULL. The only problem is that we will be never called again if m_start() returns NULL, so this is simply pointless and misleading. Otoh, ->show() methods m->version = 0 if vma == tail_vma and this is just wrong, we want -1 in this case. And in fact we also want -1 if ->vm_next == NULL and ->tail_vma == NULL. And it is not used consistently, the "scan vmas" loop in m_start() should update last_addr too. Finally, imo the whole "last_addr" logic in m_start() looks horrible. find_vma(last_addr) is called unconditionally even if we are not going to use the result. But the main problem is that this code participates in tail_vma-or-NULL mess, and this looks simply unfixable. Remove this optimization. We will add it back after some cleanups. 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 | 35 +---------------------------------- 1 file changed, 1 insertion(+), 34 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 30aa2dd3e6f5..e182fc51ec2b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -141,20 +141,10 @@ static void vma_stop(struct proc_maps_private *priv) static void *m_start(struct seq_file *m, loff_t *pos) { struct proc_maps_private *priv = m->private; - unsigned long last_addr = m->version; struct mm_struct *mm; struct vm_area_struct *vma, *tail_vma = NULL; loff_t l = *pos; - /* - * We remember last_addr rather than next_addr to hit with - * vmacache most of the time. We have zero last_addr at - * the beginning and also after lseek. We will have -1 last_addr - * after the end of the vmas. - */ - if (last_addr == -1UL) - return NULL; - priv->task = get_pid_task(priv->pid, PIDTYPE_PID); if (!priv->task) return ERR_PTR(-ESRCH); @@ -167,12 +157,6 @@ static void *m_start(struct seq_file *m, loff_t *pos) tail_vma = get_gate_vma(mm); priv->tail_vma = tail_vma; hold_task_mempolicy(priv); - /* Start with last addr hint */ - vma = find_vma(mm, last_addr); - if (last_addr && vma) { - vma = vma->vm_next; - goto out; - } /* * Check the vma index is within the range and do @@ -193,8 +177,6 @@ static void *m_start(struct seq_file *m, loff_t *pos) if (vma) return vma; - /* End of vmas has been reached */ - m->version = (tail_vma != NULL)? 0: -1UL; if (tail_vma) return tail_vma; @@ -366,14 +348,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid) static int show_map(struct seq_file *m, void *v, int is_pid) { - struct vm_area_struct *vma = v; - struct proc_maps_private *priv = m->private; - - show_map_vma(m, vma, is_pid); - - if (m->count < m->size) /* vma is copied successfully */ - m->version = (vma != priv->tail_vma) - ? vma->vm_start : 0; + show_map_vma(m, v, is_pid); return 0; } @@ -599,7 +574,6 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) static int show_smap(struct seq_file *m, void *v, int is_pid) { - struct proc_maps_private *priv = m->private; struct vm_area_struct *vma = v; struct mem_size_stats mss; struct mm_walk smaps_walk = { @@ -652,10 +626,6 @@ static int show_smap(struct seq_file *m, void *v, int is_pid) mss.nonlinear >> 10); show_smap_vma_flags(m, vma); - - if (m->count < m->size) /* vma is copied successfully */ - m->version = (vma != priv->tail_vma) - ? vma->vm_start : 0; return 0; } @@ -1510,9 +1480,6 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid) seq_printf(m, " N%d=%lu", nid, md->node[nid]); out: seq_putc(m, '\n'); - - if (m->count < m->size) - m->version = (vma != proc_priv->tail_vma) ? vma->vm_start : 0; return 0; }