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block: improve handling of the magic discard payload

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Instead of allocating a single unused biovec for discard requests, send
them down without any payload.  Instead we allow the driver to add a
"special" payload using a biovec embedded into struct request (unioned
over other fields never used while in the driver), and overloading
the number of segments for this case.

This has a couple of advantages:

 - we don't have to allocate the bio_vec
 - the amount of special casing for discard requests in the block
   layer is significantly reduced
 - using this same scheme for other request types is trivial,
   which will be important for implementing the new WRITE_ZEROES
   op on devices where it actually requires a payload (e.g. SCSI)
 - we can get rid of playing games with the request length, as
   we'll never touch it and completions will work just fine
 - it will allow us to support ranged discard operations in the
   future by merging non-contiguous discard bios into a single
   request
 - last but not least it removes a lot of code

This patch is the common base for my WIP series for ranges discards and to
remove discard_zeroes_data in favor of always using REQ_OP_WRITE_ZEROES,
so it would be good to get it in quickly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig
2016-12-08 15:20:32 -07:00
committed by Jens Axboe
parent be07e14f96
commit f9d03f96b9
13 changed files with 76 additions and 138 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
drivers/nvme/host/pci.c
View File

@@ -302,14 +302,14 @@ static void __nvme_submit_cmd(struct nvme_queue *nvmeq,
static __le64 **iod_list(struct request *req)
{
struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
return (__le64 **)(iod->sg + req->nr_phys_segments);
return (__le64 **)(iod->sg + blk_rq_nr_phys_segments(req));
}
static int nvme_init_iod(struct request *rq, unsigned size,
struct nvme_dev *dev)
{
struct nvme_iod *iod = blk_mq_rq_to_pdu(rq);
int nseg = rq->nr_phys_segments;
int nseg = blk_rq_nr_phys_segments(rq);
if (nseg > NVME_INT_PAGES || size > NVME_INT_BYTES(dev)) {
iod->sg = kmalloc(nvme_iod_alloc_size(dev, size, nseg), GFP_ATOMIC);
@@ -339,8 +339,6 @@ static void nvme_free_iod(struct nvme_dev *dev, struct request *req)
__le64 **list = iod_list(req);
dma_addr_t prp_dma = iod->first_dma;
nvme_cleanup_cmd(req);
if (iod->npages == 0)
dma_pool_free(dev->prp_small_pool, list[0], prp_dma);
for (i = 0; i < iod->npages; i++) {
@@ -510,7 +508,7 @@ static int nvme_map_data(struct nvme_dev *dev, struct request *req,
DMA_TO_DEVICE : DMA_FROM_DEVICE;
int ret = BLK_MQ_RQ_QUEUE_ERROR;
sg_init_table(iod->sg, req->nr_phys_segments);
sg_init_table(iod->sg, blk_rq_nr_phys_segments(req));
iod->nents = blk_rq_map_sg(q, req, iod->sg);
if (!iod->nents)
goto out;
@@ -566,6 +564,7 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
}
}
nvme_cleanup_cmd(req);
nvme_free_iod(dev, req);
}
@@ -596,20 +595,20 @@ static int nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
}
}
map_len = nvme_map_len(req);
ret = nvme_init_iod(req, map_len, dev);
ret = nvme_setup_cmd(ns, req, &cmnd);
if (ret != BLK_MQ_RQ_QUEUE_OK)
return ret;
ret = nvme_setup_cmd(ns, req, &cmnd);
map_len = nvme_map_len(req);
ret = nvme_init_iod(req, map_len, dev);
if (ret != BLK_MQ_RQ_QUEUE_OK)
goto out;
goto out_free_cmd;
if (req->nr_phys_segments)
if (blk_rq_nr_phys_segments(req))
ret = nvme_map_data(dev, req, map_len, &cmnd);
if (ret != BLK_MQ_RQ_QUEUE_OK)
goto out;
goto out_cleanup_iod;
blk_mq_start_request(req);
@@ -620,14 +619,16 @@ static int nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
else
ret = BLK_MQ_RQ_QUEUE_ERROR;
spin_unlock_irq(&nvmeq->q_lock);
goto out;
goto out_cleanup_iod;
}
__nvme_submit_cmd(nvmeq, &cmnd);
nvme_process_cq(nvmeq);
spin_unlock_irq(&nvmeq->q_lock);
return BLK_MQ_RQ_QUEUE_OK;
out:
out_cleanup_iod:
nvme_free_iod(dev, req);
out_free_cmd:
nvme_cleanup_cmd(req);
return ret;
}