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nvme/pci: Fix HMB size calculation

PATCH New Keith Busch 2 participants 4 messages Jul 17, 2017 – Jul 18, 2017 NVMe

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Keith Busch

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#0 lore raw

PATCH 1/1 nvme/pci: Fix HMB size calculation

It's possible the preferred HMB size may not be a multiple of the chunk_size. This patch will set the chunk_size to the descriptor's actual length so the last iteration doesn't cause the total size to exceed the allocated HMB size.

Signed-off-by Keith Busch <keith.busch at intel.com>
---
 drivers/nvme/host/pci.c | 1 +
 1 file changed, 1 insertion(+)
drivers/nvme/host/pci.c +1 -0
index d321597..e22ffda 100644
@@ -1641,6 +1641,7 @@ static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
 		if (!bufs[i])
 			break;
 
+		chunk_size = len;
 		descs[i].addr = cpu_to_le64(dma_addr);
 		descs[i].size = cpu_to_le32(len / dev->ctrl.page_size);
 		i++;
Signature · 1 line
2.5.5
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#1 lore raw

PATCH 1/1 nvme/pci: Fix HMB size calculation

Quoted 6 lines · Keith Busch

It's possible the preferred HMB size may not be a multiple of the chunk_size. This patch will set the chunk_size to the descriptor's actual length so the last iteration doesn't cause the total size to exceed the allocated HMB size.

Signed-off-by Keith Busch <keith.busch at intel.com>
Reported-by Dan Carpenter <dan.carpenter at oracle.com>
Quoted 19 lines
---
 drivers/nvme/host/pci.c | 1 +
 1 file changed, 1 insertion(+)
drivers/nvme/host/pci.c +1 -0
index d321597..e22ffda 100644
@@ -1641,6 +1641,7 @@ static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
 		if (!bufs[i])
 			break;
 
+		chunk_size = len;
 		descs[i].addr = cpu_to_le64(dma_addr);
 		descs[i].size = cpu_to_le32(len / dev->ctrl.page_size);
 		i++;
Signature · 1 line
2.5.5
maintainer
#2 lore raw

PATCH 1/1 nvme/pci: Fix HMB size calculation

In reply to Keith Busch
Quoted 4 lines · Keith Busch

It's possible the preferred HMB size may not be a multiple of the chunk_size. This patch will set the chunk_size to the descriptor's actual length so the last iteration doesn't cause the total size to exceed the allocated HMB size.

This looks a little weird, and might do the wrong thing if we hit the retry loop after reducing chunk_size.

I suspect we just need to change to

	for (size = 0; size < preferred; size += len) {

and move len to function scope.

author
#3 lore raw

PATCH 1/1 nvme/pci: Fix HMB size calculation

Quoted 8 lines · Christoph Hellwig
Quoted 4 lines · Keith Busch

It's possible the preferred HMB size may not be a multiple of the chunk_size. This patch will set the chunk_size to the descriptor's actual length so the last iteration doesn't cause the total size to exceed the allocated HMB size.

This looks a little weird, and might do the wrong thing if we hit the retry loop after reducing chunk_size.

It may look weird when you consider the retry, but I'm pretty sure it isn't wrong. The only way you can get to the retry is if the for-loop breaks before the last interation, which means chunk_size will be unchanged. That's not immediately obvious, though, so maybe this implementation was trying to be too clever.

Quoted 5 lines

I suspect we just need to change to

	for (size = 0; size < preferred; size += len) {

and move len to function scope.

That's fine too.