Re: [PATCH v5.5 10/10] mmap locking API: rename mmap_sem to mmap_lock

[Laurent Dufour]

Le 19/05/2020 à 15:10, Michel Lespinasse a écrit :

On Mon, May 18, 2020 at 03:45:22PM +0200, Laurent Dufour wrote:

Le 24/04/2020 à 03:39, Michel Lespinasse a écrit :

Rename the mmap_sem field to mmap_lock. Any new uses of this lock
should now go through the new mmap locking api. The mmap_lock is
still implemented as a rwsem, though this could change in the future.

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c 
b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
index dc9ef302f517..701f3995f621 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
@@ -661,7 +661,7 @@ static int etnaviv_gem_userptr_get_pages(struct 
etnaviv_gem_object *etnaviv_obj)
        struct etnaviv_gem_userptr *userptr = &etnaviv_obj->userptr;
        int ret, pinned = 0, npages = etnaviv_obj->base.size >> PAGE_SHIFT;
-       might_lock_read(&current->mm->mmap_sem);
+       might_lock_read(&current->mm->mmap_lock);

Why not a mm_might_lock_read() new API to hide the mmap_lock, and add it to
the previous patch?

I'm not sure why this is needed - we may rework the lock to be
something else than rwsem, but might_lock_read should still apply to
it and make sense ? I'm not sure what the extra API would bring...

I guess at one time the API would become might_lock_read_a_range(), isn't it?
Furthermore this would hiding the lock's name which the goal of this series.