On Wed, Nov 16, 2022 at 11:26:53AM +0100, David Hildenbrand wrote:
GUP now supports reliable R/O long-term pinning in COW mappings, such that we break COW early. MAP_SHARED VMAs only use the shared zeropage so far in one corner case (DAXFS file with holes), which can be ignored because GUP does not support long-term pinning in fsdax (see check_vma_flags()).
commit cd5297b0855f ("drm/etnaviv: Use FOLL_FORCE for userptr") documents that FOLL_FORCE | FOLL_WRITE was really only used for reliable R/O pinning.
Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop using FOLL_FORCE, which is really only for ptrace access.
Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Lucas Stach l.stach@pengutronix.de Cc: Russell King linux+etnaviv@armlinux.org.uk Cc: Christian Gmeiner christian.gmeiner@gmail.com Cc: David Airlie airlied@gmail.com Signed-off-by: David Hildenbrand david@redhat.com
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Also ack for merging through whatever tree suits best, since I guess this should all land together. -Daniel
drivers/gpu/drm/etnaviv/etnaviv_gem.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c index cc386f8a7116..efe2240945d0 100644 --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c @@ -638,6 +638,7 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj) struct page **pvec = NULL; struct etnaviv_gem_userptr *userptr = &etnaviv_obj->userptr; int ret, pinned = 0, npages = etnaviv_obj->base.size >> PAGE_SHIFT;
- unsigned int gup_flags = FOLL_LONGTERM;
might_lock_read(¤t->mm->mmap_lock); @@ -648,14 +649,15 @@ static int etnaviv_gem_userptr_get_pages(struct etnaviv_gem_object *etnaviv_obj) if (!pvec) return -ENOMEM;
- if (!userptr->ro)
gup_flags |= FOLL_WRITE;- do { unsigned num_pages = npages - pinned; uint64_t ptr = userptr->ptr + pinned * PAGE_SIZE; struct page **pages = pvec + pinned;
ret = pin_user_pages_fast(ptr, num_pages,FOLL_WRITE | FOLL_FORCE | FOLL_LONGTERM,pages);
ret = pin_user_pages_fast(ptr, num_pages, gup_flags, pages);-- 2.38.1