fs/proc/task_nommu.c: shift mm_access() from m_start() to proc_maps_open()

Copy-and-paste the changes from "fs/proc/task_mmu.c: shift mm_access()
from m_start() to proc_maps_open()" into task_nommu.c.

Change maps_open() to initialize priv->mm using proc_mem_open(), m_start()
can rely on atomic_inc_not_zero(mm_users) like task_mmu.c does.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 6 deletions

diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 98c95d2833ea..9019f1de3f72 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -216,11 +216,11 @@ static void *m_start(struct seq_file *m, loff_t *pos)
         if (!priv->task)
                 return ERR_PTR(-ESRCH);
 
-        mm = mm_access(priv->task, PTRACE_MODE_READ);
-        if (!mm || IS_ERR(mm)) {
+        mm = priv->mm;
+        if (!mm || !atomic_inc_not_zero(&mm->mm_users)) {
                 put_task_struct(priv->task);
                 priv->task = NULL;
-                return mm;
+                return NULL;
         }
         down_read(&mm->mmap_sem);
 
@@ -270,14 +270,34 @@ static int maps_open(struct inode *inode, struct file *file,
 {
         struct proc_maps_private *priv;
 
-        priv = __seq_open_private(file, ops, sizeof(struct proc_maps_private));
+        priv = __seq_open_private(file, ops, sizeof(*priv));
         if (!priv)
                 return -ENOMEM;
 
         priv->pid = proc_pid(inode);
+        priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
+        if (IS_ERR(priv->mm)) {
+                int err = PTR_ERR(priv->mm);
+
+                seq_release_private(inode, file);
+                return err;
+        }
+
         return 0;
 }
 
+
+static int map_release(struct inode *inode, struct file *file)
+{
+        struct seq_file *seq = file->private_data;
+        struct proc_maps_private *priv = seq->private;
+
+        if (priv->mm)
+                mmdrop(priv->mm);
+
+        return seq_release_private(inode, file);
+}
+
 static int pid_maps_open(struct inode *inode, struct file *file)
 {
         return maps_open(inode, file, &proc_pid_maps_ops);
@@ -292,13 +312,13 @@ const struct file_operations proc_pid_maps_operations = {
         .open           = pid_maps_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
-        .release        = seq_release_private,
+        .release        = map_release,
 };
 
 const struct file_operations proc_tid_maps_operations = {
         .open           = tid_maps_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
-        .release        = seq_release_private,
+        .release        = map_release,
 };