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

Add a separate flag to encode that the transfer is using the small
page sized pool, and use a normal 0..n count for the number of
descriptors.

Contains improvements and suggestions from Kanchan Joshi
<joshi.k@samsung.com> and Leon Romanovsky <leon@kernel.org>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Leon Romanovsky <leon@kernel.org>

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index b880168ab5204251aecf2f535e25944015d585af..5017d6c565196070dc4b1bd7a6a9d1a6683a9958 100644 (file)
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -229,6 +229,9 @@ struct nvme_queue {
 enum nvme_iod_flags {
        /* this command has been aborted by the timeout handler */
        IOD_ABORTED             = 1U << 0,
+
+       /* uses the small descriptor pool */
+       IOD_SMALL_DESCRIPTOR            = 1U << 1,
 };
 
 /*
@@ -238,7 +241,7 @@ struct nvme_iod {
        struct nvme_request req;
        struct nvme_command cmd;
        u8 flags;
-       s8 nr_descriptors;
+       u8 nr_descriptors;
        unsigned int dma_len;   /* length of single DMA segment mapping */
        dma_addr_t first_dma;
        dma_addr_t meta_dma;
@@ -589,13 +592,27 @@ static inline bool nvme_pci_use_sgls(struct nvme_dev *dev, struct request *req,
        return true;
 }
 
-static void nvme_free_prps(struct nvme_queue *nvmeq, struct request *req)
+static inline struct dma_pool *nvme_dma_pool(struct nvme_queue *nvmeq,
+               struct nvme_iod *iod)
+{
+       if (iod->flags & IOD_SMALL_DESCRIPTOR)
+               return nvmeq->descriptor_pools.small;
+       return nvmeq->descriptor_pools.large;
+}
+
+static void nvme_free_descriptors(struct nvme_queue *nvmeq, struct request *req)
 {
        const int last_prp = NVME_CTRL_PAGE_SIZE / sizeof(__le64) - 1;
        struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
        dma_addr_t dma_addr = iod->first_dma;
        int i;
 
+       if (iod->nr_descriptors == 1) {
+               dma_pool_free(nvme_dma_pool(nvmeq, iod), iod->descriptors[0],
+                               dma_addr);
+               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]);
@@ -620,15 +637,7 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct nvme_queue *nvmeq,
        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(nvmeq->descriptor_pools.small,
-                               iod->descriptors[0], iod->first_dma);
-       else if (iod->nr_descriptors == 1)
-               dma_pool_free(nvmeq->descriptor_pools.large,
-                               iod->descriptors[0], iod->first_dma);
-       else
-               nvme_free_prps(nvmeq, req);
+       nvme_free_descriptors(nvmeq, req);
        mempool_free(iod->sgt.sgl, dev->iod_mempool);
 }
 
@@ -650,7 +659,6 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_queue *nvmeq,
                struct request *req, struct nvme_rw_command *cmnd)
 {
        struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-       struct dma_pool *pool;
        int length = blk_rq_payload_bytes(req);
        struct scatterlist *sg = iod->sgt.sgl;
        int dma_len = sg_dma_len(sg);
@@ -658,7 +666,7 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_queue *nvmeq,
        int offset = dma_addr & (NVME_CTRL_PAGE_SIZE - 1);
        __le64 *prp_list;
        dma_addr_t prp_dma;
-       int nprps, i;
+       int i;
 
        length -= (NVME_CTRL_PAGE_SIZE - offset);
        if (length <= 0) {
@@ -680,27 +688,23 @@ static blk_status_t nvme_pci_setup_prps(struct nvme_queue *nvmeq,
                goto done;
        }
 
-       nprps = DIV_ROUND_UP(length, NVME_CTRL_PAGE_SIZE);
-       if (nprps <= (256 / 8)) {
-               pool = nvmeq->descriptor_pools.small;
-               iod->nr_descriptors = 0;
-       } else {
-               pool = nvmeq->descriptor_pools.large;
-               iod->nr_descriptors = 1;
-       }
+       if (DIV_ROUND_UP(length, NVME_CTRL_PAGE_SIZE) <=
+           256 / sizeof(__le64))
+               iod->flags |= IOD_SMALL_DESCRIPTOR;
 
-       prp_list = dma_pool_alloc(pool, GFP_ATOMIC, &prp_dma);
-       if (!prp_list) {
-               iod->nr_descriptors = -1;
+       prp_list = dma_pool_alloc(nvme_dma_pool(nvmeq, iod), GFP_ATOMIC,
+                       &prp_dma);
+       if (!prp_list)
                return BLK_STS_RESOURCE;
-       }
-       iod->descriptors[0] = prp_list;
+       iod->descriptors[iod->nr_descriptors++] = prp_list;
        iod->first_dma = prp_dma;
        i = 0;
        for (;;) {
                if (i == NVME_CTRL_PAGE_SIZE >> 3) {
                        __le64 *old_prp_list = prp_list;
-                       prp_list = dma_pool_alloc(pool, GFP_ATOMIC, &prp_dma);
+
+                       prp_list = dma_pool_alloc(nvmeq->descriptor_pools.large,
+                                       GFP_ATOMIC, &prp_dma);
                        if (!prp_list)
                                goto free_prps;
                        iod->descriptors[iod->nr_descriptors++] = prp_list;
@@ -727,7 +731,7 @@ done:
        cmnd->dptr.prp2 = cpu_to_le64(iod->first_dma);
        return BLK_STS_OK;
 free_prps:
-       nvme_free_prps(nvmeq, req);
+       nvme_free_descriptors(nvmeq, req);
        return BLK_STS_RESOURCE;
 bad_sgl:
        WARN(DO_ONCE(nvme_print_sgl, iod->sgt.sgl, iod->sgt.nents),
@@ -756,7 +760,6 @@ static blk_status_t nvme_pci_setup_sgls(struct nvme_queue *nvmeq,
                struct request *req, struct nvme_rw_command *cmd)
 {
        struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-       struct dma_pool *pool;
        struct nvme_sgl_desc *sg_list;
        struct scatterlist *sg = iod->sgt.sgl;
        unsigned int entries = iod->sgt.nents;
@@ -771,21 +774,14 @@ static blk_status_t nvme_pci_setup_sgls(struct nvme_queue *nvmeq,
                return BLK_STS_OK;
        }
 
-       if (entries <= (256 / sizeof(struct nvme_sgl_desc))) {
-               pool = nvmeq->descriptor_pools.small;
-               iod->nr_descriptors = 0;
-       } else {
-               pool = nvmeq->descriptor_pools.large;
-               iod->nr_descriptors = 1;
-       }
+       if (entries <= 256 / sizeof(*sg_list))
+               iod->flags |= IOD_SMALL_DESCRIPTOR;
 
-       sg_list = dma_pool_alloc(pool, GFP_ATOMIC, &sgl_dma);
-       if (!sg_list) {
-               iod->nr_descriptors = -1;
+       sg_list = dma_pool_alloc(nvme_dma_pool(nvmeq, iod), GFP_ATOMIC,
+                       &sgl_dma);
+       if (!sg_list)
                return BLK_STS_RESOURCE;
-       }
-
-       iod->descriptors[0] = sg_list;
+       iod->descriptors[iod->nr_descriptors++] = sg_list;
        iod->first_dma = sgl_dma;
 
        nvme_pci_sgl_set_seg(&cmd->dptr.sgl, sgl_dma, entries);
@@ -982,7 +978,7 @@ static blk_status_t nvme_prep_rq(struct nvme_dev *dev, struct request *req)
        blk_status_t ret;
 
        iod->flags = 0;
-       iod->nr_descriptors = -1;
+       iod->nr_descriptors = 0;
        iod->sgt.nents = 0;
        iod->meta_sgt.nents = 0;