[RFC PATCH 5/7] nvme-pci: remove struct nvme_descriptor

[Leon Romanovsky]

From: Christoph Hellwig <hch at lst.de>

There is no real point in having a union of two pointer types here, just
use a void pointer as we mix and match types between the arms of the
union between the allocation and freeing side already.

Also rename the nr_allocations field to nr_descriptors to better describe
what it does.

Signed-off-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Leon Romanovsky <leonro at nvidia.com>
---
 drivers/nvme/host/pci.c | 51 ++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 29 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 4b9fda0b1d9a..ba077a42cbba 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -43,7 +43,8 @@
  */
 #define NVME_MAX_KB_SZ	8192
 #define NVME_MAX_SEGS	128
-#define NVME_MAX_NR_ALLOCATIONS	5
+
+#define NVME_MAX_NR_DESCRIPTORS		5
 
 static int use_threaded_interrupts;
 module_param(use_threaded_interrupts, int, 0444);
@@ -216,28 +217,20 @@ struct nvme_queue {
 	struct completion delete_done;
 };
 
-union nvme_descriptor {
-	struct nvme_sgl_desc	*sg_list;
-	__le64			*prp_list;
-};
-
 /*
  * The nvme_iod describes the data in an I/O.
- *
- * The sg pointer contains the list of PRP/SGL chunk allocations in addition
- * to the actual struct scatterlist.
  */
 struct nvme_iod {
 	struct nvme_request req;
 	struct nvme_command cmd;
 	bool aborted;
-	s8 nr_allocations;	/* PRP list pool allocations. 0 means small
-				   pool in use */
+	/* # of PRP/SGL descriptors: (0 for small pool) */
+	s8 nr_descriptors;
 	unsigned int dma_len;	/* length of single DMA segment mapping */
 	dma_addr_t first_dma;
 	dma_addr_t meta_dma;
 	struct sg_table sgt;
-	union nvme_descriptor list[NVME_MAX_NR_ALLOCATIONS];
+	void *descriptors[NVME_MAX_NR_DESCRIPTORS];
 };
 
 static inline unsigned int nvme_dbbuf_size(struct nvme_dev *dev)
@@ -528,8 +521,8 @@ static void nvme_free_prps(struct nvme_dev *dev, struct request *req)
 	dma_addr_t dma_addr = iod->first_dma;
 	int i;
 
-	for (i = 0; i < iod->nr_allocations; i++) {
-		__le64 *prp_list = iod->list[i].prp_list;
+	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]);
 
 		dma_pool_free(dev->prp_page_pool, prp_list, dma_addr);
@@ -551,11 +544,11 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
 
 	dma_unmap_sgtable(dev->dev, &iod->sgt, rq_dma_dir(req), 0);
 
-	if (iod->nr_allocations == 0)
-		dma_pool_free(dev->prp_small_pool, iod->list[0].sg_list,
+	if (iod->nr_descriptors == 0)
+		dma_pool_free(dev->prp_small_pool, iod->descriptors[0],
 			      iod->first_dma);
-	else if (iod->nr_allocations == 1)
-		dma_pool_free(dev->prp_page_pool, iod->list[0].sg_list,
+	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);
@@ -613,18 +606,18 @@ 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_allocations = 0;
+		iod->nr_descriptors = 0;
 	} else {
 		pool = dev->prp_page_pool;
-		iod->nr_allocations = 1;
+		iod->nr_descriptors = 1;
 	}
 
 	prp_list = dma_pool_alloc(pool, GFP_ATOMIC, &prp_dma);
 	if (!prp_list) {
-		iod->nr_allocations = -1;
+		iod->nr_descriptors = -1;
 		return BLK_STS_RESOURCE;
 	}
-	iod->list[0].prp_list = prp_list;
+	iod->descriptors[0] = prp_list;
 	iod->first_dma = prp_dma;
 	i = 0;
 	for (;;) {
@@ -633,7 +626,7 @@ 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)
 				goto free_prps;
-			iod->list[iod->nr_allocations++].prp_list = prp_list;
+			iod->descriptors[iod->nr_descriptors++] = prp_list;
 			prp_list[0] = old_prp_list[i - 1];
 			old_prp_list[i - 1] = cpu_to_le64(prp_dma);
 			i = 1;
@@ -703,19 +696,19 @@ 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_allocations = 0;
+		iod->nr_descriptors = 0;
 	} else {
 		pool = dev->prp_page_pool;
-		iod->nr_allocations = 1;
+		iod->nr_descriptors = 1;
 	}
 
 	sg_list = dma_pool_alloc(pool, GFP_ATOMIC, &sgl_dma);
 	if (!sg_list) {
-		iod->nr_allocations = -1;
+		iod->nr_descriptors = -1;
 		return BLK_STS_RESOURCE;
 	}
 
-	iod->list[0].sg_list = sg_list;
+	iod->descriptors[0] = sg_list;
 	iod->first_dma = sgl_dma;
 
 	nvme_pci_sgl_set_seg(&cmd->dptr.sgl, sgl_dma, entries);
@@ -841,7 +834,7 @@ static blk_status_t nvme_prep_rq(struct nvme_dev *dev, struct request *req)
 	blk_status_t ret;
 
 	iod->aborted = false;
-	iod->nr_allocations = -1;
+	iod->nr_descriptors = -1;
 	iod->sgt.nents = 0;
 
 	ret = nvme_setup_cmd(req->q->queuedata, req);
@@ -3626,7 +3619,7 @@ static int __init nvme_init(void)
 	BUILD_BUG_ON(IRQ_AFFINITY_MAX_SETS < 2);
 	BUILD_BUG_ON(NVME_MAX_SEGS > SGES_PER_PAGE);
 	BUILD_BUG_ON(sizeof(struct scatterlist) * NVME_MAX_SEGS > PAGE_SIZE);
-	BUILD_BUG_ON(nvme_pci_npages_prp() > NVME_MAX_NR_ALLOCATIONS);
+	BUILD_BUG_ON(nvme_pci_npages_prp() > NVME_MAX_NR_DESCRIPTORS);
 
 	return pci_register_driver(&nvme_driver);
 }
-- 
2.46.2