Re: [PATCH] vfs: move dentry shrinking outside the inode lock in 'rmdir()'

[Al Viro <viro@zeniv.linux.org.uk>]

On Sat, May 11, 2024 at 11:42:34AM -0700, Linus Torvalds wrote:

> so we have another level of locking going on, and my patch only moved
> the dcache pruning outside the lock of the directory we're removing
> (not outside the lock of the directory that contains the removed
> directory).
> 
> And that outside lock is the much more important one, I bet.

... and _that_ is where taking d_delete outside of the lock might
take an unpleasant analysis of a lot of code.

We have places where we assume that holding the parent locked
will prevent ->d_inode changes of children.  It might be possible
to get rid of that, but it will take a non-trivial amount of work.

In any case, I think the original poster said that parent directories
were not removed, so I doubt that rmdir() behaviour is relevant for
their load.