[Intel-xe] [PATCH v4 4/6] drm/xe/ggtt: prime ggtt->lock against FS_RECLAIM

[Matthew Auld]

Increase the sensitivity of the ggtt->lock by priming it against
FS_RECLAIM, such that allocating memory while holding will result in
lockdep splats.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/xe/xe_ggtt.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
index f986e8218820..e25eb70d44f6 100644
--- a/drivers/gpu/drm/xe/xe_ggtt.c
+++ b/drivers/gpu/drm/xe/xe_ggtt.c
@@ -90,6 +90,16 @@ static void ggtt_fini_noalloc(struct drm_device *drm, void *arg)
 	xe_bo_unpin_map_no_vm(ggtt->scratch);
 }
 
+static void primelockdep(struct xe_ggtt *ggtt)
+{
+	if (!IS_ENABLED(CONFIG_LOCKDEP))
+		return;
+
+	fs_reclaim_acquire(GFP_KERNEL);
+	might_lock(&ggtt->lock);
+	fs_reclaim_release(GFP_KERNEL);
+}
+
 int xe_ggtt_init_noalloc(struct xe_gt *gt, struct xe_ggtt *ggtt)
 {
 	struct xe_device *xe = gt_to_xe(gt);
@@ -132,6 +142,7 @@ int xe_ggtt_init_noalloc(struct xe_gt *gt, struct xe_ggtt *ggtt)
 	drm_mm_init(&ggtt->mm, xe_wopcm_size(xe),
 		    ggtt->size - xe_wopcm_size(xe));
 	mutex_init(&ggtt->lock);
+	primelockdep(ggtt);
 
 	return drmm_add_action_or_reset(&xe->drm, ggtt_fini_noalloc, ggtt);
 }
-- 
2.40.1