[PATCH RFC v5 3/6] iommu/arm-smmu-v3: Delay stream allocation to inside the mutex

[Peng Fan (OSS)]

From: Peng Fan <peng.fan@xxxxxxx>

Move arm_smmu_stream allocation from upfront (before the mutex) into
the mutex-protected loop in arm_smmu_insert_master(). Instead of
pre-allocating all stream objects and then inserting them into the RB
tree, first look up whether the SID already exists in the tree. Only
allocate and insert a new stream when no existing entry is found, then
avoid unnecessary allocations when bridged PCI devices produce duplicated
IDs. Prepare the code for a subsequent patch that will reuse existing
streams when stream IDs are shared across masters.

The sort is also moved after the mutex section, since streams are now
populated inside the loop rather than beforehand.

Assisted-by: LLM
Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 102 +++++++++++++++-------------
 1 file changed, 53 insertions(+), 49 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 9d34eac196a65..69c2c3596b06a 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4110,52 +4110,29 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu,
 		return -ENOMEM;
 	}
 
-	for (i = 0; i < fwspec->num_ids; i++) {
-		struct arm_smmu_stream *new_stream;
-
-		new_stream = kzalloc_obj(*new_stream, GFP_KERNEL);
-		if (!new_stream) {
-			ret = -ENOMEM;
-			goto out_free_streams;
-		}
-		new_stream->id = fwspec->ids[i];
-		new_stream->master = master;
-		master->streams[i] = new_stream;
-	}
-
-	/* Put the ids into order for sorted to_merge/to_unref arrays */
-	sort(master->streams, master->num_streams,
-	     sizeof(master->streams[0]), arm_smmu_stream_id_cmp,
-	     NULL);
-
-	/*
-	 * Clear after sorting: RB_CLEAR_NODE() records the node's own address,
-	 * which sort_nonatomic() invalidates by relocating the entries.
-	 */
-	for (i = 0; i < fwspec->num_ids; i++)
-		RB_CLEAR_NODE(&master->streams[i]->node);
-
 	mutex_lock(&smmu->streams_mutex);
 	for (i = 0; i < fwspec->num_ids; i++) {
-		struct arm_smmu_stream *new_stream = master->streams[i];
+		struct arm_smmu_stream *stream;
 		struct rb_node *existing;
-		u32 sid = new_stream->id;
+		u32 sid = fwspec->ids[i];
 
 		ret = arm_smmu_init_sid_strtab(smmu, sid);
 		if (ret)
 			break;
 
-		/* Insert into SID tree */
-		existing = rb_find_add(&new_stream->node, &smmu->streams,
-				       arm_smmu_streams_cmp_node);
+		existing = rb_find(&sid, &smmu->streams,
+				   arm_smmu_streams_cmp_key);
 		if (existing) {
 			struct arm_smmu_master *existing_master =
 				rb_entry(existing, struct arm_smmu_stream, node)
 					->master;
 
 			/* Bridged PCI devices may end up with duplicated IDs */
-			if (existing_master == master)
+			if (existing_master == master) {
+				master->streams[i] = rb_entry(existing,
+					struct arm_smmu_stream, node);
 				continue;
+			}
 
 			dev_warn(master->dev,
 				 "Aliasing StreamID 0x%x (from %s) unsupported, expect DMA to be broken\n",
@@ -4163,45 +4140,72 @@ static int arm_smmu_insert_master(struct arm_smmu_device *smmu,
 			ret = -ENODEV;
 			break;
 		}
+
+		stream = kzalloc_obj(*stream, GFP_KERNEL);
+		if (!stream) {
+			ret = -ENOMEM;
+			break;
+		}
+		stream->id = sid;
+		stream->master = master;
+
+		rb_find_add(&stream->node, &smmu->streams,
+			    arm_smmu_streams_cmp_node);
+		master->streams[i] = stream;
 	}
 
 	if (ret) {
-		for (i--; i >= 0; i--)
-			if (!RB_EMPTY_NODE(&master->streams[i]->node))
-				rb_erase(&master->streams[i]->node,
-					 &smmu->streams);
+		for (i--; i >= 0; i--) {
+			int j;
+
+			if (!master->streams[i])
+				continue;
+			/* Skip duplicated SID pointers already freed */
+			for (j = 0; j < i; j++)
+				if (master->streams[j] == master->streams[i])
+					break;
+			if (j < i)
+				continue;
+			rb_erase(&master->streams[i]->node, &smmu->streams);
+			kfree(master->streams[i]);
+		}
 		mutex_unlock(&smmu->streams_mutex);
-		goto out_free_streams;
+		kfree(master->streams);
+		kfree(master->build_invs);
+		return ret;
 	}
 	mutex_unlock(&smmu->streams_mutex);
 
-	return 0;
+	/* Put the ids into order for sorted to_merge/to_unref arrays */
+	sort(master->streams, master->num_streams,
+	     sizeof(master->streams[0]), arm_smmu_stream_id_cmp,
+	     NULL);
 
-out_free_streams:
-	for (i = 0; i < master->num_streams; i++)
-		kfree(master->streams[i]);
-	kfree(master->streams);
-	kfree(master->build_invs);
-	return ret;
+	return 0;
 }
 
 static void arm_smmu_remove_master(struct arm_smmu_master *master)
 {
 	int i;
 	struct arm_smmu_device *smmu = master->smmu;
-	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(master->dev);
 
 	if (!smmu || !master->streams)
 		return;
 
 	mutex_lock(&smmu->streams_mutex);
-	for (i = 0; i < fwspec->num_ids; i++)
-		if (!RB_EMPTY_NODE(&master->streams[i]->node))
-			rb_erase(&master->streams[i]->node, &smmu->streams);
-	mutex_unlock(&smmu->streams_mutex);
+	for (i = 0; i < master->num_streams; i++) {
+		int j;
 
-	for (i = 0; i < master->num_streams; i++)
+		/* Skip duplicated SID pointers already freed */
+		for (j = 0; j < i; j++)
+			if (master->streams[j] == master->streams[i])
+				break;
+		if (j < i)
+			continue;
+		rb_erase(&master->streams[i]->node, &smmu->streams);
 		kfree(master->streams[i]);
+	}
+	mutex_unlock(&smmu->streams_mutex);
 
 	kfree(master->streams);
 	kfree(master->build_invs);

-- 
2.34.1