Convert the driver to the modern blk-mq framework.
As byproduct we get rid of our open coded restart logic and let
blk-mq handle it.

Signed-off-by: Richard Weinberger <richard@nod.at>
---
 arch/um/drivers/ubd_kern.c | 178 +++++++++++++++++++++++----------------------
 1 file changed, 93 insertions(+), 85 deletions(-)

diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index b55fe9bf5d3e..deceb8022a28 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c

@@ -23,6 +23,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/blkdev.h>
+#include <linux/blk-mq.h>
 #include <linux/ata.h>
 #include <linux/hdreg.h>
 #include <linux/cdrom.h>

@@ -142,7 +143,6 @@ struct cow {
 #define MAX_SG 64
 
 struct ubd {
-	struct list_head restart;
 	/* name (and fd, below) of the file opened for writing, either the
 	 * backing or the cow file. */
 	char *file;

@@ -156,9 +156,12 @@ struct ubd {
 	struct cow cow;
 	struct platform_device pdev;
 	struct request_queue *queue;
+	struct blk_mq_tag_set tag_set;
 	spinlock_t lock;
+};
+
+struct ubd_pdu {
 	struct scatterlist sg[MAX_SG];
-	struct request *request;
 	int start_sg, end_sg;
 	sector_t rq_pos;
 };

@@ -182,10 +185,6 @@ struct ubd {
 	.shared =		0, \
 	.cow =			DEFAULT_COW, \
 	.lock =			__SPIN_LOCK_UNLOCKED(ubd_devs.lock), \
-	.request =		NULL, \
-	.start_sg =		0, \
-	.end_sg =		0, \
-	.rq_pos =		0, \
 }
 
 /* Protected by ubd_lock */

@@ -196,6 +195,12 @@ static int fake_ide = 0;
 static struct proc_dir_entry *proc_ide_root = NULL;
 static struct proc_dir_entry *proc_ide = NULL;
 
+static blk_status_t ubd_queue_rq(struct blk_mq_hw_ctx *hctx,
+				 const struct blk_mq_queue_data *bd);
+static int ubd_init_request(struct blk_mq_tag_set *set,
+			    struct request *req, unsigned int hctx_idx,
+			    unsigned int numa_node);
+
 static void make_proc_ide(void)
 {
 	proc_ide_root = proc_mkdir("ide", NULL);

@@ -448,11 +453,8 @@ __uml_help(udb_setup,
 "    in the boot output.\n\n"
 );
 
-static void do_ubd_request(struct request_queue * q);
-
 /* Only changed by ubd_init, which is an initcall. */
 static int thread_fd = -1;
-static LIST_HEAD(restart);
 
 /* Function to read several request pointers at a time
 * handling fractional reads if (and as) needed

@@ -510,9 +512,6 @@ static int bulk_req_safe_read(
 /* Called without dev->lock held, and only in interrupt context. */
 static void ubd_handler(void)
 {
-	struct ubd *ubd;
-	struct list_head *list, *next_ele;
-	unsigned long flags;
 	int n;
 	int count;
 

@@ -532,23 +531,17 @@ static void ubd_handler(void)
 			return;
 		}
 		for (count = 0; count < n/sizeof(struct io_thread_req *); count++) {
-			blk_end_request(
-				(*irq_req_buffer)[count]->req,
-				BLK_STS_OK,
-				(*irq_req_buffer)[count]->length
-			);
-			kfree((*irq_req_buffer)[count]);
+			struct io_thread_req *io_req = (*irq_req_buffer)[count];
+			int err = io_req->error ? BLK_STS_IOERR : BLK_STS_OK;
+
+			if (!blk_update_request(io_req->req, err, io_req->length))
+				__blk_mq_end_request(io_req->req, err);
+
+			kfree(io_req);
 		}
 	}
-	reactivate_fd(thread_fd, UBD_IRQ);
 
-	list_for_each_safe(list, next_ele, &restart){
-		ubd = container_of(list, struct ubd, restart);
-		list_del_init(&ubd->restart);
-		spin_lock_irqsave(&ubd->lock, flags);
-		do_ubd_request(ubd->queue);
-		spin_unlock_irqrestore(&ubd->lock, flags);
-	}
+	reactivate_fd(thread_fd, UBD_IRQ);
 }
 
 static irqreturn_t ubd_intr(int irq, void *dev)

@@ -869,6 +862,7 @@ static void ubd_device_release(struct device *dev)
 	struct ubd *ubd_dev = dev_get_drvdata(dev);
 
 	blk_cleanup_queue(ubd_dev->queue);
+	blk_mq_free_tag_set(&ubd_dev->tag_set);
 	*ubd_dev = ((struct ubd) DEFAULT_UBD);
 }
 

@@ -911,6 +905,11 @@ static int ubd_disk_register(int major, u64 size, int unit,
 
 #define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
 
+static const struct blk_mq_ops ubd_mq_ops = {
+	.queue_rq = ubd_queue_rq,
+	.init_request = ubd_init_request,
+};