From: Christoph Hellwig <hch@lst.de>
Date: Sat, 5 Oct 2024 17:21:33 +0000 (+0200)
Subject: nvme-pci: use a smarter encoding for small prp pool allocations
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=12f024ef5c78fa8592b65b2bad99c3f02b24e9ad;p=users%2Fhch%2Fblock.git

nvme-pci: use a smarter encoding for small prp pool allocations

Make 0 mean no allocations and -1 "small pool" instead of vice versa.
With that only the small pool needs special casing.

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

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 5d67be831c2e..e9869221300d 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -223,7 +223,7 @@ struct nvme_iod {
 	struct nvme_request req;
 	struct nvme_command cmd;
 	bool aborted;
-	/* # of PRP/SGL descriptors: (0 for small pool) */
+	/* # of PRP/SGL descriptors: (-1 for small pool) */
 	s8 nr_descriptors;
 	unsigned int dma_len;	/* length of single DMA segment mapping */
 	dma_addr_t first_dma;
@@ -520,6 +520,12 @@ static void nvme_free_prps(struct nvme_dev *dev, struct request *req)
 	dma_addr_t dma_addr = iod->first_dma;
 	int i;
 
+	if (iod->nr_descriptors == -1) {
+		dma_pool_free(dev->prp_small_pool, iod->descriptors[0],
+			      iod->first_dma);
+		return;
+	}
+
 	for (i = 0; i < iod->nr_descriptors; i++) {
 		__le64 *prp_list = iod->descriptors[i];
 		dma_addr_t next_dma_addr = le64_to_cpu(prp_list[last_prp]);
@@ -542,15 +548,7 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
 	WARN_ON_ONCE(!iod->sgt.nents);
 
 	dma_unmap_sgtable(dev->dev, &iod->sgt, rq_dma_dir(req), 0);
-
-	if (iod->nr_descriptors == 0)
-		dma_pool_free(dev->prp_small_pool, iod->descriptors[0],
-			      iod->first_dma);
-	else if (iod->nr_descriptors == 1)
-		dma_pool_free(dev->prp_page_pool, iod->descriptors[0],
-			      iod->first_dma);
-	else
-		nvme_free_prps(dev, req);
+	nvme_free_prps(dev, req);
 	mempool_free(iod->sgt.sgl, dev->iod_mempool);
 }
 
@@ -605,7 +603,7 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_dev *dev,
 	nprps = DIV_ROUND_UP(length, NVME_CTRL_PAGE_SIZE);
 	if (nprps <= (256 / 8)) {
 		pool = dev->prp_small_pool;
-		iod->nr_descriptors = 0;
+		iod->nr_descriptors = -1;
 	} else {
 		pool = dev->prp_page_pool;
 		iod->nr_descriptors = 1;
@@ -613,7 +611,7 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_dev *dev,
 
 	prp_list = dma_pool_alloc(pool, GFP_ATOMIC, &prp_dma);
 	if (!prp_list) {
-		iod->nr_descriptors = -1;
+		iod->nr_descriptors = 0;
 		return BLK_STS_RESOURCE;
 	}
 	iod->descriptors[0] = prp_list;
@@ -695,7 +693,7 @@ static blk_status_t nvme_pci_setup_sgls(struct nvme_dev *dev,
 
 	if (entries <= (256 / sizeof(struct nvme_sgl_desc))) {
 		pool = dev->prp_small_pool;
-		iod->nr_descriptors = 0;
+		iod->nr_descriptors = -1;
 	} else {
 		pool = dev->prp_page_pool;
 		iod->nr_descriptors = 1;
@@ -703,7 +701,7 @@ static blk_status_t nvme_pci_setup_sgls(struct nvme_dev *dev,
 
 	sg_list = dma_pool_alloc(pool, GFP_ATOMIC, &sgl_dma);
 	if (!sg_list) {
-		iod->nr_descriptors = -1;
+		iod->nr_descriptors = 0;
 		return BLK_STS_RESOURCE;
 	}
 
@@ -833,7 +831,7 @@ static blk_status_t nvme_prep_rq(struct nvme_dev *dev, struct request *req)
 	blk_status_t ret;
 
 	iod->aborted = false;
-	iod->nr_descriptors = -1;
+	iod->nr_descriptors = 0;
 	iod->sgt.nents = 0;
 
 	ret = nvme_setup_cmd(req->q->queuedata, req);