[RFC v3 8/8] drm/xe/bo: Add purgeable shrinker state helpers

[Arvind Yadav <arvind.yadav@intel.com>]

Encapsulate TTM purgeable flag updates and shrinker page accounting
into helper functions. This prevents desynchronization between the
TTM tt->purgeable flag and the shrinker's page bucket counters.

Without these helpers, direct manipulation of xe_ttm_tt->purgeable
risks forgetting to update the corresponding shrinker counters,
leading to incorrect memory pressure calculations.

Add xe_bo_set_purgeable_shrinker() and xe_bo_clear_purgeable_shrinker()
which atomically update both the TTM flag and transfer pages between
the shrinkable and purgeable buckets.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
 drivers/gpu/drm/xe/xe_bo.c         | 60 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_bo.h         |  3 ++
 drivers/gpu/drm/xe/xe_vm_madvise.c | 13 +++++--
 3 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 31b2fa490440..fa29e4951af5 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -843,6 +843,66 @@ static void xe_bo_set_purged(struct xe_bo *bo)
 	atomic_set(&bo->madv_purgeable, XE_MADV_PURGEABLE_PURGED);
 }
 
+/**
+ * xe_bo_set_purgeable_shrinker() - Mark BO purgeable and update shrinker
+ * @bo: Buffer object
+ *
+ * Transfers pages from shrinkable to purgeable bucket. Shrinker can now
+ * discard pages immediately without swapping. Caller holds BO lock.
+ */
+void xe_bo_set_purgeable_shrinker(struct xe_bo *bo)
+{
+	struct ttm_buffer_object *ttm_bo = &bo->ttm;
+	struct ttm_tt *tt = ttm_bo->ttm;
+	struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
+	struct xe_ttm_tt *xe_tt;
+
+	xe_bo_assert_held(bo);
+
+	if (!tt || !ttm_tt_is_populated(tt))
+		return;
+
+	xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
+
+	if (!xe_tt->purgeable) {
+		xe_tt->purgeable = true;
+		/* Transfer pages from shrinkable to purgeable count */
+		xe_shrinker_mod_pages(xe->mem.shrinker,
+				      -(long)tt->num_pages,
+				      tt->num_pages);
+	}
+}
+
+/**
+ * xe_bo_clear_purgeable_shrinker() - Mark BO non-purgeable and update shrinker
+ * @bo: Buffer object
+ *
+ * Transfers pages from purgeable to shrinkable bucket. Shrinker must now
+ * swap pages instead of discarding. Caller holds BO lock.
+ */
+void xe_bo_clear_purgeable_shrinker(struct xe_bo *bo)
+{
+	struct ttm_buffer_object *ttm_bo = &bo->ttm;
+	struct ttm_tt *tt = ttm_bo->ttm;
+	struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
+	struct xe_ttm_tt *xe_tt;
+
+	xe_bo_assert_held(bo);
+
+	if (!tt || !ttm_tt_is_populated(tt))
+		return;
+
+	xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
+
+	if (xe_tt->purgeable) {
+		xe_tt->purgeable = false;
+		/* Transfer pages from purgeable to shrinkable count */
+		xe_shrinker_mod_pages(xe->mem.shrinker,
+				      tt->num_pages,
+				      -(long)tt->num_pages);
+	}
+}
+
 /**
  * xe_ttm_bo_purge() - Purge buffer object backing store
  * @ttm_bo: The TTM buffer object to purge
diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
index 1090a60f6ef6..9c5ccd03af7b 100644
--- a/drivers/gpu/drm/xe/xe_bo.h
+++ b/drivers/gpu/drm/xe/xe_bo.h
@@ -270,6 +270,9 @@ static inline bool xe_bo_madv_is_dontneed(struct xe_bo *bo)
 	return atomic_read(&bo->madv_purgeable) == XE_MADV_PURGEABLE_DONTNEED;
 }
 
+void xe_bo_set_purgeable_shrinker(struct xe_bo *bo);
+void xe_bo_clear_purgeable_shrinker(struct xe_bo *bo);
+
 static inline void xe_bo_unpin_map_no_vm(struct xe_bo *bo)
 {
 	if (likely(bo)) {
diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c
index 868be570664d..cdbbdfda5928 100644
--- a/drivers/gpu/drm/xe/xe_vm_madvise.c
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
@@ -257,12 +257,16 @@ void xe_bo_recheck_purgeable_on_vma_unbind(struct xe_bo *bo)
 
 	if (xe_bo_all_vmas_dontneed(bo)) {
 		/* All VMAs are DONTNEED - mark BO purgeable */
-		if (current_state != XE_MADV_PURGEABLE_DONTNEED)
+		if (current_state != XE_MADV_PURGEABLE_DONTNEED) {
 			atomic_set(&bo->madv_purgeable, XE_MADV_PURGEABLE_DONTNEED);
+			xe_bo_set_purgeable_shrinker(bo);
+		}
 	} else {
 		/* At least one VMA is WILLNEED - BO must not be purgeable */
-		if (current_state != XE_MADV_PURGEABLE_WILLNEED)
+		if (current_state != XE_MADV_PURGEABLE_WILLNEED) {
 			atomic_set(&bo->madv_purgeable, XE_MADV_PURGEABLE_WILLNEED);
+			xe_bo_clear_purgeable_shrinker(bo);
+		}
 	}
 }
 
@@ -307,13 +311,16 @@ static bool xe_vm_madvise_purgeable_bo(struct xe_device *xe, struct xe_vm *vm,
 			vmas[i]->purgeable_state = XE_MADV_PURGEABLE_WILLNEED;
 			 /* Mark VMA WILLNEED - BO becomes non-purgeable immediately */
 			atomic_set(&bo->madv_purgeable, XE_MADV_PURGEABLE_WILLNEED);
+			xe_bo_clear_purgeable_shrinker(bo);
 			break;
 		case DRM_XE_VMA_PURGEABLE_STATE_DONTNEED:
 			vmas[i]->purgeable_state = XE_MADV_PURGEABLE_DONTNEED;
 
 			/* Mark BO purgeable only if all VMAs are DONTNEED */
-			if (xe_bo_all_vmas_dontneed(bo))
+			if (xe_bo_all_vmas_dontneed(bo)) {
 				atomic_set(&bo->madv_purgeable, XE_MADV_PURGEABLE_DONTNEED);
+				xe_bo_set_purgeable_shrinker(bo);
+			}
 			break;
 		default:
 			drm_warn(&vm->xe->drm, "Invalid madvice value = %d\n",
-- 
2.43.0