[PATCH v4 6/9] gpu/drm/radeon: optimize out the case when a range is updated to read only

[jglisse at redhat.com]

From: Jérôme Glisse <jglisse at redhat.com>

When range of virtual address is updated read only and corresponding
user ptr object are already read only it is pointless to do anything.
Optimize this case out.

Signed-off-by: Jérôme Glisse <jglisse at redhat.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: Jan Kara <jack at suse.cz>
Cc: Felix Kuehling <Felix.Kuehling at amd.com>
Cc: Jason Gunthorpe <jgg at mellanox.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Matthew Wilcox <mawilcox at microsoft.com>
Cc: Ross Zwisler <zwisler at kernel.org>
Cc: Dan Williams <dan.j.williams at intel.com>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Radim Krčmář <rkrcmar at redhat.com>
Cc: Michal Hocko <mhocko at kernel.org>
Cc: Ralph Campbell <rcampbell at nvidia.com>
Cc: John Hubbard <jhubbard at nvidia.com>
Cc: kvm at vger.kernel.org
Cc: dri-devel at lists.freedesktop.org
Cc: linux-rdma at vger.kernel.org
Cc: linux-fsdevel at vger.kernel.org
Cc: Arnd Bergmann <arnd at arndb.de>
---
 drivers/gpu/drm/radeon/radeon_mn.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_mn.c b/drivers/gpu/drm/radeon/radeon_mn.c
index b3019505065a..f77294f58e63 100644
--- a/drivers/gpu/drm/radeon/radeon_mn.c
+++ b/drivers/gpu/drm/radeon/radeon_mn.c
@@ -124,6 +124,7 @@ static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
 	struct radeon_mn *rmn = container_of(mn, struct radeon_mn, mn);
 	struct ttm_operation_ctx ctx = { false, false };
 	struct interval_tree_node *it;
+	bool update_to_read_only;
 	unsigned long end;
 	int ret = 0;
 
@@ -138,6 +139,8 @@ static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
 	else if (!mutex_trylock(&rmn->lock))
 		return -EAGAIN;
 
+	update_to_read_only = mmu_notifier_range_update_to_read_only(range);
+
 	it = interval_tree_iter_first(&rmn->objects, range->start, end);
 	while (it) {
 		struct radeon_mn_node *node;
@@ -153,10 +156,20 @@ static int radeon_mn_invalidate_range_start(struct mmu_notifier *mn,
 		it = interval_tree_iter_next(it, range->start, end);
 
 		list_for_each_entry(bo, &node->bos, mn_list) {
+			bool read_only;
 
 			if (!bo->tbo.ttm || bo->tbo.ttm->state != tt_bound)
 				continue;
 
+			/*
+			 * If it is already read only and we are updating to
+			 * read only then we do not need to change anything.
+			 * So save time and skip this one.
+			 */
+			read_only = radeon_ttm_tt_is_readonly(bo->tbo.ttm);
+			if (update_to_read_only && read_only)
+				continue;
+
 			r = radeon_bo_reserve(bo, true);
 			if (r) {
 				DRM_ERROR("(%ld) failed to reserve user bo\n", r);
-- 
2.17.2