proc: introduce proc_mem_open()

Extract the mm_access() code from __mem_open() into the new helper,
proc_mem_open(), the next patch will add another caller.

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>

1 files changed, 21 insertions, 15 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index baf852b648ad..4c542b907754 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -632,29 +632,35 @@ static const struct file_operations proc_single_file_operations = {
         .release        = single_release,
 };
 
-static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
+
+struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode)
 {
-        struct task_struct *task = get_proc_task(file_inode(file));
-        struct mm_struct *mm;
+        struct task_struct *task = get_proc_task(inode);
+        struct mm_struct *mm = ERR_PTR(-ESRCH);
 
-        if (!task)
-                return -ESRCH;
+        if (task) {
+                mm = mm_access(task, mode);
+                put_task_struct(task);
 
-        mm = mm_access(task, mode);
-        put_task_struct(task);
+                if (!IS_ERR_OR_NULL(mm)) {
+                        /* ensure this mm_struct can't be freed */
+                        atomic_inc(&mm->mm_count);
+                        /* but do not pin its memory */
+                        mmput(mm);
+                }
+        }
+
+        return mm;
+}
+
+static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
+{
+        struct mm_struct *mm = proc_mem_open(inode, mode);
 
         if (IS_ERR(mm))
                 return PTR_ERR(mm);
 
-        if (mm) {
-                /* ensure this mm_struct can't be freed */
-                atomic_inc(&mm->mm_count);
-                /* but do not pin its memory */
-                mmput(mm);
-        }
-
         file->private_data = mm;
-
         return 0;
 }