On Fri, Mar 15, 2019 at 09:56:32AM +1100, Tobin C. Harding wrote:
> Hi,
>
> I'm not able to understand the locking order in dcache. dcache has been
> around for a while so clearly its right and I'm wrong.
>
> Could someone please explain to me how the locking order commented at
> the top of the file is not violated in the following:
>
> From top of fs/dcache.c
>
> * If there is an ancestor relationship:
> * dentry->d_parent->...->d_parent->d_lock
> * ...
> * dentry->d_parent->d_lock
> * dentry->d_lock
>
This is a more simple example
static struct dentry *dentry_kill(struct dentry *dentry)
__releases(dentry->d_lock)
{
...
slow_positive:
spin_unlock(&dentry->d_lock);
spin_lock(&inode->i_lock);
spin_lock(&dentry->d_lock);
parent = lock_parent(dentry);
...
thanks,
Tobin.
