[PATCHv2] blk-mq-dma: always initialize dma state

[PATCHv2] blk-mq-dma: always initialize dma state

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

Ensure the dma state is initialized when we're not using the contiguous
iova, otherwise the caller may be using a stale state from a previous
request that could use the coalesed iova allocation.

Fixes: 2f6b2565d43cdb5 ("block: accumulate memory segment gaps per bio")
Reported-by: Sebastian Ott <sebott@redhat.com>
Tested-by: Sebastian Ott <sebott@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
v1->v2:

  Simpler logic to always do the state initialization

 block/blk-mq-dma.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index e9108ccaf4b06..6dc7a3c23ac8d 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -199,6 +199,7 @@ static bool blk_dma_map_iter_start(struct request *req, struct device *dma_dev,
 	if (blk_can_dma_map_iova(req, dma_dev) &&
 	    dma_iova_try_alloc(dma_dev, state, vec.paddr, total_len))
 		return blk_rq_dma_map_iova(req, dma_dev, state, iter, &vec);
+	memset(state, 0, sizeof(*state));
 	return blk_dma_map_direct(req, dma_dev, iter, &vec);
 }
 
-- 
2.47.3

Re: [PATCHv2] blk-mq-dma: always initialize dma state

[Christoph Hellwig]

On Wed, Dec 10, 2025 at 02:43:46AM -0800, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> Ensure the dma state is initialized when we're not using the contiguous
> iova, otherwise the caller may be using a stale state from a previous
> request that could use the coalesed iova allocation.

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCHv2] blk-mq-dma: always initialize dma state

[Jens Axboe]

On Wed, 10 Dec 2025 02:43:46 -0800, Keith Busch wrote:
> Ensure the dma state is initialized when we're not using the contiguous
> iova, otherwise the caller may be using a stale state from a previous
> request that could use the coalesed iova allocation.
> 
> 

Applied, thanks!

[1/1] blk-mq-dma: always initialize dma state
      commit: a0750fae73c55112ea11a4867bee40f11e679405

Best regards,
-- 
Jens Axboe