Re: [PATCH 4/4] fs/dcache: Avoid the try_lock loops in dentry_kill()

[Linus Torvalds]

On Fri, Feb 16, 2018 at 2:32 PM, John Ogness <john.ogness@xxxxxxxxxxxxx> wrote:
>
> lock_parent() already has the problem you are referring to. Callers are
> required to recheck the dentry contents and check the returned parent
> because they do not know if the trylock succeeded. See
> d_prune_aliases(), for example.

What are you talking about?

lock_parent() does the nice "spin_trylock succeeded" special case.

Yes, it will then do the "unlock dentry, do the parent first, then
re-check" too, and callers may need to worry about it.

But that's not what I'm complaining about in your patch. You remove
the simple case, and make dentry_kill() do the "recheck in case I
dropped" every single time.

It's the "turn a simple case into a complex case" that I absolutely detest.

The fact that there are _other_ complex cases doesn't make it any
better. The whole "but Bobby does it too" thing is not a defense.
Would you jump off a bridge just because your friend did it?

               Linus