Add a comment in chrdev_open()

I stared at this code for a while and almost deleted it before
understanding crept into my slow brain.  Hopefully this makes life easier
for the next person to happen on it.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 68e510b..a54d693 100644 (file)
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -373,6 +373,8 @@ static int chrdev_open(struct inode *inode, struct file *filp)
                        return -ENXIO;
                new = container_of(kobj, struct cdev, kobj);
                spin_lock(&cdev_lock);
+               /* Check i_cdev again in case somebody beat us to it while
+                  we dropped the lock. */
                p = inode->i_cdev;
                if (!p) {
                        inode->i_cdev = p = new;