Re: [PATCH 10/11] VFS: take a shared lock for create/remove directory operations.

Al Viro
2024-12-23T05:19:43Z

On Fri, Dec 20, 2024 at 01:54:28PM +1100, NeilBrown wrote:

> Once the exclusive "update" lock is obtained on the dentry we must make
> sure it wasn't unlinked or renamed while we slept. If it was we repeat
> the lookup.

> + if (
> + /* Was unlinked while we waited ?*/
> + d_unhashed(dentry) ||
> + /* Or was dentry renamed ?? */
> + dentry->d_parent != base ||
> + dentry->d_name.hash != last->hash ||
> + !d_same_name(dentry, base, last)
> + ) {
> + rcu_read_unlock();
> + spin_unlock(&dentry->d_lock);
> + lock_map_release(&dentry->d_update_map);
> + dput(dentry);
> + goto retry;
> + }
> + rcu_read_unlock();
> + }
> + dentry->d_flags |= DCACHE_PAR_UPDATE;
> + spin_unlock(&dentry->d_lock);

... and now __d_unalias() moves it to new place, making all the checks
you've just done completely useless.