[RFC PATCH 5/5] iommupt: Return real page count to the shrinker core

[Pranjal Shrivastava]

Update the count op to return real nr_pages that can be reclaimed.

Signed-off-by: Pranjal Shrivastava <praan@xxxxxxxxxx>
---
 drivers/iommu/generic_pt/iommu_pt.h | 1 +
 drivers/iommu/generic_pt/shrinker.c | 9 ++++-----
 include/linux/generic_pt/iommu.h    | 5 +++++
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/generic_pt/iommu_pt.h b/drivers/iommu/generic_pt/iommu_pt.h
index e5ee419f2f0b..4386caf3f713 100644
--- a/drivers/iommu/generic_pt/iommu_pt.h
+++ b/drivers/iommu/generic_pt/iommu_pt.h
@@ -1115,6 +1115,7 @@ static __maybe_unused int __unmap_range(struct pt_range *range, void *arg,
 
 				xa_store(&iommu->domain.reclaim_list, range->va,
 					 virt_to_ioptdesc(pts.table), GFP_ATOMIC);
+				atomic_long_inc(&iommu->nr_reclaimable);
 			}
 
 			gather_add_leaf(&unmap->pending, &pts);
diff --git a/drivers/iommu/generic_pt/shrinker.c b/drivers/iommu/generic_pt/shrinker.c
index 66169fb5db71..a27e171b5e80 100644
--- a/drivers/iommu/generic_pt/shrinker.c
+++ b/drivers/iommu/generic_pt/shrinker.c
@@ -43,11 +43,7 @@ static unsigned long generic_pt_shrinker_count(struct shrinker *shrink,
 
 	mutex_lock(&generic_pt_domains_list_lock);
 	list_for_each_entry(iommu, &generic_pt_domains_list, shrinker_list) {
-		struct iommu_domain *domain = &iommu->domain;
-
-		/* TODO: Return real nr_pages here! */
-		if (!xa_empty(&domain->reclaim_list))
-			count += 1;
+		count += atomic_long_read(&iommu->nr_reclaimable);
 	}
 	mutex_unlock(&generic_pt_domains_list_lock);
 
@@ -78,15 +74,18 @@ static unsigned long generic_pt_shrinker_scan(struct shrinker *shrink,
 				if (iommu->ops->sever_branch(iommu, iova, virt_to_phys(virt))) {
 					/* Successfully severed, queue for freeing */
 					xa_erase(&domain->reclaim_list, iova);
+					atomic_long_dec(&iommu->nr_reclaimable);
 					iommu_pages_list_add(&free_list, virt);
 					freed_count++;
 				} else {
 					/* We raced with map, abort pruning */
 					xa_erase(&domain->reclaim_list, iova);
+					atomic_long_dec(&iommu->nr_reclaimable);
 				}
 			} else {
 				/* Not empty anymore, remove from list */
 				xa_erase(&domain->reclaim_list, iova);
+				atomic_long_dec(&iommu->nr_reclaimable);
 			}
 		}
 
diff --git a/include/linux/generic_pt/iommu.h b/include/linux/generic_pt/iommu.h
index 95bf9d4f0b6e..3c94745bded0 100644
--- a/include/linux/generic_pt/iommu.h
+++ b/include/linux/generic_pt/iommu.h
@@ -69,6 +69,11 @@ struct pt_iommu {
 	 * @shrinker_list: Node for the generic_pt global shrinker list
 	 */
 	struct list_head shrinker_list;
+
+	/**
+	 * @nr_reclaimable: Count of empty directories waiting in reclaim_list
+	 */
+	atomic_long_t nr_reclaimable;
 };
 
 extern struct srcu_struct generic_pt_srcu;
-- 
2.56.0.rc1.315.gc6ed9934b7-goog