Re: [PATCH v2 0/4] lockdep/crossrelease: Apply crossrelease to page locks

[Matthew Wilcox]

On Mon, Dec 04, 2017 at 02:16:19PM +0900, Byungchul Park wrote:
> For now, wait_for_completion() / complete() works with lockdep, add
> lock_page() / unlock_page() and its family to lockdep support.
> 
> Changes from v1
>  - Move lockdep_map_cross outside of page_ext to make it flexible
>  - Prevent allocating lockdep_map per page by default
>  - Add a boot parameter allowing the allocation for debugging
> 
> Byungchul Park (4):
>   lockdep: Apply crossrelease to PG_locked locks
>   lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked
>   lockdep: Move data of CONFIG_LOCKDEP_PAGELOCK from page to page_ext
>   lockdep: Add a boot parameter enabling to track page locks using
>     lockdep and disable it by default

I don't like the way you've structured this patch series; first adding
the lockdep map to struct page, then moving it to page_ext.

I also don't like it that you've made CONFIG_LOCKDEP_PAGELOCK not
individually selectable.  I might well want a kernel with crosslock
support, but only for completions.