From f9d03f96b988002027d4b28ea1b7a24729a4c9b5 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 8 Dec 2016 15:20:32 -0700 Subject: block: improve handling of the magic discard payload 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 Signed-off-by: Jens Axboe --- drivers/nvme/target/loop.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/nvme/target') diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c index 57ded6b3ed8a..9aaa70071ae5 100644 --- a/drivers/nvme/target/loop.c +++ b/drivers/nvme/target/loop.c @@ -185,13 +185,13 @@ static int nvme_loop_queue_rq(struct blk_mq_hw_ctx *hctx, if (blk_rq_bytes(req)) { iod->sg_table.sgl = iod->first_sgl; ret = sg_alloc_table_chained(&iod->sg_table, - req->nr_phys_segments, iod->sg_table.sgl); + blk_rq_nr_phys_segments(req), + iod->sg_table.sgl); if (ret) return BLK_MQ_RQ_QUEUE_BUSY; iod->req.sg = iod->sg_table.sgl; iod->req.sg_cnt = blk_rq_map_sg(req->q, req, iod->sg_table.sgl); - BUG_ON(iod->req.sg_cnt > req->nr_phys_segments); } blk_mq_start_request(req); -- cgit v1.2.3