drm/pagemap_util: Ensure proper cache lock management on free

For the sake of consistency, ensure that the cache lock is always
unlocked after drm_pagemap_cache_fini. Spinlocks typically disable
preemption and if the code-path missing the unlock is hit, preemption
will remain disabled even if the lock is subsequently freed.

Fixes static analysis issue.

v2:
- Use requested code flow (Maarten)

v3:
- Clear cache->dpagemap (Matt Brost, Maarten)

v4:
- Reword commit message (Thomas)

Fixes: 77f14f2f2d73f ("drm/pagemap: Add a drm_pagemap cache and shrinker")
Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Thomas Hellstrom <thomas.hellstrom@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20260316151555.7553-2-jonathan.cavitt@intel.com

1 files changed, 5 insertions, 9 deletions

diff --git a/drivers/gpu/drm/drm_pagemap_util.c b/drivers/gpu/drm/drm_pagemap_util.c
index 14ddb948a32e..6111d90a38e2 100644
--- a/drivers/gpu/drm/drm_pagemap_util.c
+++ b/drivers/gpu/drm/drm_pagemap_util.c
@@ -65,18 +65,14 @@ static void drm_pagemap_cache_fini(void *arg)
 	drm_dbg(cache->shrinker->drm, "Destroying dpagemap cache.\n");
 	spin_lock(&cache->lock);
 	dpagemap = cache->dpagemap;
-	if (!dpagemap) {
-		spin_unlock(&cache->lock);
-		goto out;
-	}
+	cache->dpagemap = NULL;
+	if (dpagemap && !drm_pagemap_shrinker_cancel(dpagemap))
+		dpagemap = NULL;
+	spin_unlock(&cache->lock);
 
-	if (drm_pagemap_shrinker_cancel(dpagemap)) {
-		cache->dpagemap = NULL;
-		spin_unlock(&cache->lock);
+	if (dpagemap)
 		drm_pagemap_destroy(dpagemap, false);
-	}
 
-out:
 	mutex_destroy(&cache->lookup_mutex);
 	kfree(cache);
 }