[PATCH RFC v2 0/2] pidfs: use maple tree

[Liam R. Howlett]

* Christian Brauner <brauner at kernel.org> [241209 08:47]:
> Hey,
> 
> Ok, I wanted to give this another try as I'd really like to rely on the
> maple tree supporting ULONG_MAX when BITS_PER_LONG is 64 as it makes
> things a lot simpler overall.
> 
> As Willy didn't want additional users relying on an external lock I made
> it so that we don't have to and can just use the mtree lock.
> 
> However, I need an irq safe variant which is why I added support for
> this into the maple tree.
> 
> This is pullable from
> https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git work.pidfs.maple_tree


I've been meaning to respond to this thread.

I believe the flag is to tell the internal code what lock to use.  If
you look at mas_nomem(), there is a retry loop that will drop the lock
to allocate and retry the operation.  That function needs to support the
flag and use the correct lock/unlock.

The mas_lock()/mas_unlock() needs a mas_lock_irq()/mas_unlock_irq()
variant, which would be used in the correct context.

Does that make sense?

Thanks,
Liam

> 
> Thanks!
> Christian
> 
> ---
> Christian Brauner (2):
>       maple_tree: make MT_FLAGS_LOCK_IRQ do something
>       pidfs: use maple tree
> 
>  fs/pidfs.c                 | 52 +++++++++++++++++++++++++++-------------------
>  include/linux/maple_tree.h | 16 ++++++++++++--
>  kernel/pid.c               | 34 +++++++++++++++---------------
>  3 files changed, 62 insertions(+), 40 deletions(-)
> ---
> base-commit: 963c8e506c6d4769d04fcb64d4bf783e4ef6093e
> change-id: 20241206-work-pidfs-maple_tree-b322ff5399b7
>