From b8c20a9b85b057c850f63ee4c63531a356d8596a Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 9 Oct 2014 15:25:41 -0700 Subject: [PATCH] fs/proc/task_mmu.c: reintroduce m->version logic Add the "last_addr" optimization back. Like before, every ->show() method checks !seq_overflow() and sets m->version = vma->vm_start. However, it also checks that m_next_vma(vma) != NULL, otherwise it sets m->version = -1 for the lockless "EOF" fast-path in m_start(). m_start() can simply do find_vma() + m_next_vma() if last_addr is not zero, the code looks clear and simple and this case is clearly separated from "scan vmas" path. 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 | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index fef398948462..c7228c2326d1 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -146,13 +146,24 @@ m_next_vma(struct proc_maps_private *priv, struct vm_area_struct *vma) return vma->vm_next ?: priv->tail_vma; } +static void m_cache_vma(struct seq_file *m, struct vm_area_struct *vma) +{ + if (m->count < m->size) /* vma is copied successfully */ + m->version = m_next_vma(m->private, vma) ? vma->vm_start : -1UL; +} + static void *m_start(struct seq_file *m, loff_t *ppos) { struct proc_maps_private *priv = m->private; + unsigned long last_addr = m->version; struct mm_struct *mm; struct vm_area_struct *vma; unsigned int pos = *ppos; + /* See m_cache_vma(). Zero at the start or after lseek. */ + if (last_addr == -1UL) + return NULL; + priv->task = get_pid_task(priv->pid, PIDTYPE_PID); if (!priv->task) return ERR_PTR(-ESRCH); @@ -165,6 +176,13 @@ static void *m_start(struct seq_file *m, loff_t *ppos) hold_task_mempolicy(priv); priv->tail_vma = get_gate_vma(mm); + if (last_addr) { + vma = find_vma(mm, last_addr); + if (vma && (vma = m_next_vma(priv, vma))) + return vma; + } + + m->version = 0; if (pos < mm->map_count) { for (vma = mm->mmap; pos; pos--) vma = vma->vm_next; @@ -340,6 +358,7 @@ done: static int show_map(struct seq_file *m, void *v, int is_pid) { show_map_vma(m, v, is_pid); + m_cache_vma(m, v); return 0; } @@ -617,6 +636,7 @@ static int show_smap(struct seq_file *m, void *v, int is_pid) mss.nonlinear >> 10); show_smap_vma_flags(m, vma); + m_cache_vma(m, vma); return 0; } @@ -1471,6 +1491,7 @@ 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'); + m_cache_vma(m, vma); return 0; } -- 2.20.1