From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Date: Wed, 16 Nov 2022 10:49:43 +0000 Subject: Re: [PATCH mm-unstable v1 14/20] drm/etnaviv: remove FOLL_FORCE usage Message-Id: List-Id: References: <20221116102659.70287-1-david@redhat.com> <20221116102659.70287-15-david@redhat.com> In-Reply-To: <20221116102659.70287-15-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kselftest@vger.kernel.org, Linus Torvalds , Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Vlastimil Babka , Matthew Wilcox , Mike Kravetz , Muchun Song , Shuah Khan , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann , Christoph Hellwig , Alex Williamson , Daniel Vetter , Russell King , Christian Gmeiner 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 > Cc: Lucas Stach > Cc: Russell King > Cc: Christian Gmeiner > Cc: David Airlie > Signed-off-by: David Hildenbrand Reviewed-by: Daniel Vetter 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 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch