[RFC PATCH 5/8] nvmet: add Verify emulation support for bdev-ns

[Chaitanya Kulkarni <chaitanyak@xxxxxxxxxx>]

From: Chaitanya Kulkarni <kch@xxxxxxxxxx>

Not all devices can support verify requests which can be mapped to
the controller specific command. This patch adds a way to emulate
REQ_OP_VERIFY for NVMeOF block device namespace. We add a new
workqueue to offload the emulation with the help of
__blkdev_emulate_verify().

Signed-off-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
---
 drivers/nvme/target/core.c        | 12 +++++++-
 drivers/nvme/target/io-cmd-bdev.c | 51 ++++++++++++++++++++++++++-----
 drivers/nvme/target/nvmet.h       |  3 ++
 3 files changed, 57 insertions(+), 9 deletions(-)

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 8ce4d59cc9e7..8a17a6479073 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -16,6 +16,7 @@
 #include "nvmet.h"
 
 struct workqueue_struct *buffered_io_wq;
+struct workqueue_struct *verify_wq;
 static const struct nvmet_fabrics_ops *nvmet_transports[NVMF_TRTYPE_MAX];
 static DEFINE_IDA(cntlid_ida);
 
@@ -1546,11 +1547,17 @@ static int __init nvmet_init(void)
 
 	nvmet_ana_group_enabled[NVMET_DEFAULT_ANA_GRPID] = 1;
 
+	verify_wq = alloc_workqueue("nvmet-verify-wq", WQ_MEM_RECLAIM, 0);
+	if (!verify_wq) {
+		error = -ENOMEM;
+		goto out;
+	}
+
 	buffered_io_wq = alloc_workqueue("nvmet-buffered-io-wq",
 			WQ_MEM_RECLAIM, 0);
 	if (!buffered_io_wq) {
 		error = -ENOMEM;
-		goto out;
+		goto out_free_verify_work_queue;
 	}
 
 	error = nvmet_init_discovery();
@@ -1566,6 +1573,8 @@ static int __init nvmet_init(void)
 	nvmet_exit_discovery();
 out_free_work_queue:
 	destroy_workqueue(buffered_io_wq);
+out_free_verify_work_queue:
+	destroy_workqueue(verify_wq);
 out:
 	return error;
 }
@@ -1576,6 +1585,7 @@ static void __exit nvmet_exit(void)
 	nvmet_exit_discovery();
 	ida_destroy(&cntlid_ida);
 	destroy_workqueue(buffered_io_wq);
+	destroy_workqueue(verify_wq);
 
 	BUILD_BUG_ON(sizeof(struct nvmf_disc_rsp_page_entry) != 1024);
 	BUILD_BUG_ON(sizeof(struct nvmf_disc_rsp_page_hdr) != 1024);
diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index 5a888cdadfea..80b8e7bfd1ae 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -433,25 +433,60 @@ static void nvmet_bdev_execute_write_zeroes(struct nvmet_req *req)
 	}
 }
 
-static void nvmet_bdev_execute_verify(struct nvmet_req *req)
+static void __nvmet_req_to_verify_sectors(struct nvmet_req *req,
+		sector_t *sects, sector_t *nr_sects)
 {
 	struct nvme_verify_cmd *verify = &req->cmd->verify;
+
+	*sects = le64_to_cpu(verify->slba) << (req->ns->blksize_shift - 9);
+	*nr_sects = (((sector_t)le16_to_cpu(verify->length) + 1) <<
+			(req->ns->blksize_shift - 9));
+}
+
+static void nvmet_bdev_emulate_verify_work(struct work_struct *w)
+{
+	struct nvmet_req *req = container_of(w, struct nvmet_req, b.work);
+	sector_t nr_sector;
+	sector_t sector;
+	int ret = 0;
+
+	__nvmet_req_to_verify_sectors(req, &sector, &nr_sector);
+	if (!nr_sector)
+		goto out;
+
+	ret = blkdev_emulate_verify(req->ns->bdev, sector, nr_sector,
+			GFP_KERNEL);
+out:
+	nvmet_req_complete(req,
+			   blk_to_nvme_status(req, errno_to_blk_status(ret)));
+}
+
+static void nvmet_bdev_submit_emulate_verify(struct nvmet_req *req)
+{
+	INIT_WORK(&req->b.work, nvmet_bdev_emulate_verify_work);
+	queue_work(verify_wq, &req->b.work);
+}
+
+
+static void nvmet_bdev_execute_verify(struct nvmet_req *req)
+{
 	struct bio *bio = NULL;
 	sector_t nr_sector;
 	sector_t sector;
-	int ret;
+	int ret = 0;
 
 	if (!nvmet_check_transfer_len(req, 0))
 		return;
 
+	/* offload emulation */
 	if (!bdev_verify_sectors(req->ns->bdev)) {
-		nvmet_req_complete(req, NVME_SC_INTERNAL | NVME_SC_DNR);
+		nvmet_bdev_submit_emulate_verify(req);
 		return;
 	}
 
-	sector = le64_to_cpu(verify->slba) << (req->ns->blksize_shift - 9);
-	nr_sector = (((sector_t)le16_to_cpu(verify->length) + 1) <<
-			(req->ns->blksize_shift - 9));
+	__nvmet_req_to_verify_sectors(req, &sector, &nr_sector);
+	if (!nr_sector)
+		goto out;
 
 	ret = __blkdev_issue_verify(req->ns->bdev, sector, nr_sector,
 			GFP_KERNEL, &bio);
@@ -459,9 +494,9 @@ static void nvmet_bdev_execute_verify(struct nvmet_req *req)
 		bio->bi_private = req;
 		bio->bi_end_io = nvmet_bio_done;
 		submit_bio(bio);
-	} else {
-		nvmet_req_complete(req, errno_to_nvme_status(req, ret));
 	}
+out:
+	nvmet_req_complete(req, errno_to_nvme_status(req, ret));
 }
 
 u16 nvmet_bdev_parse_io_cmd(struct nvmet_req *req)
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 8776dd1a0490..7f3f584b1e7b 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -323,6 +323,8 @@ struct nvmet_req {
 	union {
 		struct {
 			struct bio      inline_bio;
+			/* XXX: should we take work out of union ? */
+			struct work_struct      work;
 		} b;
 		struct {
 			bool			mpool_alloc;
@@ -355,6 +357,7 @@ struct nvmet_req {
 };
 
 extern struct workqueue_struct *buffered_io_wq;
+extern struct workqueue_struct *verify_wq;
 
 static inline void nvmet_set_result(struct nvmet_req *req, u32 result)
 {
-- 
2.22.1