Re: [PATCH 1/8] mmap locking API: initial implementation as rwsem wrappers

[Jason Gunthorpe]

On Thu, Mar 26, 2020 at 12:02:29AM -0700, Michel Lespinasse wrote:

> +static inline bool mmap_is_locked(struct mm_struct *mm)
> +{
> +	return rwsem_is_locked(&mm->mmap_sem) != 0;
> +}

I've been wondering if the various VM_BUG(rwsem_is_locked()) would be
better as lockdep expressions? Certainly when lockdep is enabled it
should be preferred, IMHO.

So, I think if inlines are to be introduced this should be something
similar to netdev's ASSERT_RTNL which seems to have worked well.

Maybe ASSERT_MMAP_SEM_READ/WRITE/HELD() and do the VM_BUG or
lockdep_is_held as appropriate?

Jason