[PATCH mm-unstable v1 14/20] drm/etnaviv: remove FOLL_FORCE usage

From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: 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 <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	John Hubbard <jhubbard@nvidia.com>, Peter Xu <peterx@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Hugh Dickins <hughd@google.com>, Nadav Amit <namit@vmware.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Matthew Wilcox <willy@infradead.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Muchun Song <songmuchun@bytedance.com>,
	Shuah Khan <shuah@kernel.org>,
	Lucas Stach <l.stach@pengutronix.de>,
	David Airlie <airlied@gmail.com>,
	Oded Gabbay <ogabbay@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Christoph Hellwig <hch@infradead.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Russell King <linux+etnaviv@armlinux.org.uk>,
	Christian Gmeiner <christian.gmeiner@gmail.com>
Subject: [PATCH mm-unstable v1 14/20] drm/etnaviv: remove FOLL_FORCE usage
Date: Wed, 16 Nov 2022 11:26:53 +0100	[thread overview]
Message-ID: <20221116102659.70287-15-david@redhat.com> (raw)
In-Reply-To: <20221116102659.70287-1-david@redhat.com>

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(-)

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(&current->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

