| Message ID | 20221116102659.70287-15-david@redhat.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O long-term pinning) | expand |
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); > if (ret < 0) { > unpin_user_pages(pvec, pinned); > kvfree(pvec); > -- > 2.38.1 >
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); if (ret < 0) { unpin_user_pages(pvec, pinned); kvfree(pvec);
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> --- drivers/gpu/drm/etnaviv/etnaviv_gem.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)