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nvme: Fixes u64 division which breaks i386 builds

PATCH New Jon Derrick 2 participants 2 messages Jul 21, 2015 – Jul 22, 2015

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Jon Derrick

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#0 lore raw

PATCH 1/1 nvme: Fixes u64 division which breaks i386 builds

Uses div_u64 for u64 division and round_down, a bitwise operation, instead of rounddown, which uses a modulus.

Signed-off-by Jon Derrick <jonathan.derrick at intel.com>

---
Hi folks. I accidentally broke i386 builds with my u64 math. This is the attempt to use safe operators instead of direct operator on u64 variables

I will, of course, be mindful of i386 builds from now on. :)

 drivers/block/nvme-core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
drivers/block/nvme-core.c +3 -2
index 82b4ffb..666e994 100644
@@ -1454,8 +1454,9 @@ static int nvme_cmb_qdepth(struct nvme_dev *dev, int nr_io_queues,
 	unsigned q_size_aligned = roundup(q_depth * entry_size, dev->page_size);
 
 	if (q_size_aligned * nr_io_queues > dev->cmb_size) {
-		q_depth = rounddown(dev->cmb_size / nr_io_queues,
-					dev->page_size) / entry_size;
+		u64 mem_per_q = div_u64(dev->cmb_size, nr_io_queues);
+		mem_per_q = round_down(mem_per_q, dev->page_size);
+		q_depth = div_u64(mem_per_q, entry_size);
 
 		/*
 		 * Ensure the reduced q_depth is above some threshold where it
Signature · 1 line
2.1.4
#1 lore raw

PATCH 1/1 nvme: Fixes u64 division which breaks i386 builds

Quoted 9 lines · Jon Derrick

Uses div_u64 for u64 division and round_down, a bitwise operation, instead of rounddown, which uses a modulus.

Signed-off-by Jon Derrick <jonathan.derrick at intel.com>

---
Hi folks. I accidentally broke i386 builds with my u64 math. This is the attempt to use safe operators instead of direct operator on u64 variables

I will, of course, be mindful of i386 builds from now on. :)

Yes, it's pain. Might be time to troll Linus to finally link against libgcc for 64-bit division helpers to avoid these issues..

Reviewed-by Christoph Hellwig <hch at lst.de>
Quoted 28 lines
 drivers/block/nvme-core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
drivers/block/nvme-core.c +3 -2
index 82b4ffb..666e994 100644
@@ -1454,8 +1454,9 @@ static int nvme_cmb_qdepth(struct nvme_dev *dev, int nr_io_queues,
 	unsigned q_size_aligned = roundup(q_depth * entry_size, dev->page_size);
 
 	if (q_size_aligned * nr_io_queues > dev->cmb_size) {
-		q_depth = rounddown(dev->cmb_size / nr_io_queues,
-					dev->page_size) / entry_size;
+		u64 mem_per_q = div_u64(dev->cmb_size, nr_io_queues);
+		mem_per_q = round_down(mem_per_q, dev->page_size);
+		q_depth = div_u64(mem_per_q, entry_size);
 
 		/*
 		 * Ensure the reduced q_depth is above some threshold where it
Signature · 7 lines
2.1.4


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