[PATCH 2/3] fs/proc/task_nommu.c: shift mm_access() from m_start() to proc_maps_open()

[Oleg Nesterov]

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.

Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
 fs/proc/task_nommu.c |   29 ++++++++++++++++++++++++-----
 1 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index c12eab3..003f2be 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);
 
@@ -274,9 +274,28 @@ static int maps_open(struct inode *inode, struct file 
*file,
                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);
@@ -291,13 +310,13 @@ 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,
 };
 
-- 
1.5.5.1

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