Re: [PATCH 4/5] mm: add and use mmap_read_lock[_killable]_nosteal() on contention

[David Hildenbrand (Arm)]

On 11/3/26 09:27, Lorenzo Stoakes (ARM) wrote:
> With down_read[_killable]_nosteal() available, it becomes possible to
> release the mmap read lock in such a way that a queued write lock always
> takes precedence.
> 
> Expose this to mm through two new wrappers - mmap_read_lock_nosteal() and
> mmap_read_lock_killable_nosteal().
> 
> Make use of this in scenarios where the mmap read lock is dropped
> explicitly for the purposes of relieving mmap_lock contention - the BPF
> task VMA iterator, and lock_next_vma_under_mmap_lock(), which is where
> /proc/$pid/smaps_rollup re-acquires the mmap lock after dropping it on
> contention and falling back from per-VMA locking.
> 
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> ---
>  include/linux/mmap_lock.h | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  kernel/bpf/task_iter.c    |  2 +-


I'd appreciate an ack from BPF folks and a confirmation that I could take this
through my tree :)


-- 
Cheers,

David