linux-kernel - [PATCH] nvme: adjust multiples of NVME_CTRL_PAGE

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Message-Id: <20240523113149.29174-1-kundan.kumar@samsung.com>
Date: Thu, 23 May 2024 17:01:49 +0530
From: Kundan Kumar <kundan.kumar@...sung.com>
To: axboe@...nel.dk, hch@....de, kbusch@...nel.org, sagi@...mberg.me
Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
	joshi.k@...sung.com, anuj20.g@...sung.com, nj.shetty@...sung.com,
	c.gameti@...sung.com, gost.dev@...sung.com, Kundan Kumar
	<kundan.kumar@...sung.com>
Subject: [PATCH] nvme: adjust multiples of NVME_CTRL_PAGE_SIZE in offset

bio_vec start offset may be relatively large particularly when large
folio gets added to the bio. A bigger offset will result in avoiding the
single-segment mapping optimization and end up using expensive
mempool_alloc further.

Rather than using absolute value, adjust bv_offset by
NVME_CTRL_PAGE_SIZE while checking if segment can be fitted into one/two
PRP entries.

Suggested-by: Christoph Hellwig <hch@....de>
Signed-off-by: Kundan Kumar <kundan.kumar@...sung.com>
---
 drivers/nvme/host/pci.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 710043086dff..102a9fb0c65f 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -778,7 +778,8 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
 		struct bio_vec bv = req_bvec(req);
 
 		if (!is_pci_p2pdma_page(bv.bv_page)) {
-			if (bv.bv_offset + bv.bv_len <= NVME_CTRL_PAGE_SIZE * 2)
+			if ((bv.bv_offset & (NVME_CTRL_PAGE_SIZE - 1)) +
+			     bv.bv_len <= NVME_CTRL_PAGE_SIZE * 2)
 				return nvme_setup_prp_simple(dev, req,
 							     &cmnd->rw, &bv);
 
-- 
2.25.1