ipc: use simple_read_from_buffer()

Also this patch kills unneccesary trailing NULL character.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 18 deletions

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 3e84b958186b..1fdc2eb2f6d8 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -314,15 +314,11 @@ static int mqueue_unlink(struct inode *dir, struct dentry *dentry)
 *       through std routines)
 */
 static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,
-                                size_t count, loff_t * off)
+                                size_t count, loff_t *off)
 {
         struct mqueue_inode_info *info = MQUEUE_I(filp->f_path.dentry->d_inode);
         char buffer[FILENT_SIZE];
-        size_t slen;
-        loff_t o;
-
-        if (!count)
-                return 0;
+        ssize_t ret;
 
         spin_lock(&info->lock);
         snprintf(buffer, sizeof(buffer),
@@ -335,21 +331,14 @@ static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,
                         pid_vnr(info->notify_owner));
         spin_unlock(&info->lock);
         buffer[sizeof(buffer)-1] = '\0';
-        slen = strlen(buffer)+1;
-
-        o = *off;
-        if (o > slen)
-                return 0;
-
-        if (o + count > slen)
-                count = slen - o;
 
-        if (copy_to_user(u_data, buffer + o, count))
-                return -EFAULT;
+        ret = simple_read_from_buffer(u_data, count, off, buffer,
+                                strlen(buffer));
+        if (ret <= 0)
+                return ret;
 
-        *off = o + count;
         filp->f_path.dentry->d_inode->i_atime = filp->f_path.dentry->d_inode->i_ctime = CURRENT_TIME;
-        return count;
+        return ret;
 }
 
 static int mqueue_flush_file(struct file *filp, fl_owner_t id)