linux-kernel - [PATCH RFC 1/1] dmaengine: ptdma: use SLAB_TYPESAFE_BY

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Message-ID: <20250411194148.247361-2-ezulian@redhat.com>
Date: Fri, 11 Apr 2025 21:41:48 +0200
From: Eder Zulian <ezulian@...hat.com>
To: Basavaraj.Natikar@....com,
	vkoul@...nel.org,
	dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: jsnitsel@...hat.com,
	ddutile@...hat.com,
	Eder Zulian <ezulian@...hat.com>
Subject: [PATCH RFC 1/1] dmaengine: ptdma: use SLAB_TYPESAFE_BY_RCU for the DMA descriptor slab

The SLAB_TYPESAFE_BY_RCU flag prevents a change of type for objects
allocated from the slab cache (although the memory may be reallocated to
a completetly different object of the same type.) Moreover, when the
last reference to an object is dropped the finalization code must not
run until all __rcu pointers referencing the object have been updated,
and then a grace period has passed.

Signed-off-by: Eder Zulian <ezulian@...hat.com>
---
 drivers/dma/amd/ptdma/ptdma-dmaengine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/amd/ptdma/ptdma-dmaengine.c b/drivers/dma/amd/ptdma/ptdma-dmaengine.c
index 715ac3ae067b..b70dd1b0b9fb 100644
--- a/drivers/dma/amd/ptdma/ptdma-dmaengine.c
+++ b/drivers/dma/amd/ptdma/ptdma-dmaengine.c
@@ -597,7 +597,8 @@ int pt_dmaengine_register(struct pt_device *pt)
 
 	pt->dma_desc_cache = kmem_cache_create(desc_cache_name,
 					       sizeof(struct pt_dma_desc), 0,
-					       SLAB_HWCACHE_ALIGN, NULL);
+					       SLAB_HWCACHE_ALIGN |
+					       SLAB_TYPESAFE_BY_RCU, NULL);
 	if (!pt->dma_desc_cache) {
 		ret = -ENOMEM;
 		goto err_cache;
-- 
2.49.0