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>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 68e510b88457..a54d69369b2f 100644
--- 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;