mg_disk: dequeue and track in-flight request

mg_disk has at most single request in flight per device.  Till now,
whenever it needs to access the in-flight request it called
elv_next_request().  This patch makes mg_disk track the in-flight
request directly using mg_host->req and dequeue it when processing
starts.

q->queuedata is set to mg_host so that mg_host can be determined
without fetching request from the queue.

[ Impact: dequeue in-flight request, one elv_next_request() per request ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: unsik Kim <donari75@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 59 insertions, 50 deletions

diff --git a/drivers/block/mg_disk.c b/drivers/block/mg_disk.c
index be323880f24a..1ca5d1423fa3 100644
--- a/drivers/block/mg_disk.c
+++ b/drivers/block/mg_disk.c
@@ -135,6 +135,7 @@ struct mg_host {
         struct device *dev;
 
         struct request_queue *breq;
+        struct request *req;
         spinlock_t lock;
         struct gendisk *gd;
 
@@ -171,17 +172,27 @@ struct mg_host {
 
 static void mg_request(struct request_queue *);
 
+static bool mg_end_request(struct mg_host *host, int err, unsigned int nr_bytes)
+{
+        if (__blk_end_request(host->req, err, nr_bytes))
+                return true;
+
+        host->req = NULL;
+        return false;
+}
+
+static bool mg_end_request_cur(struct mg_host *host, int err)
+{
+        return mg_end_request(host, err, blk_rq_cur_bytes(host->req));
+}
+
 static void mg_dump_status(const char *msg, unsigned int stat,
                 struct mg_host *host)
 {
         char *name = MG_DISK_NAME;
-        struct request *req;
 
-        if (host->breq) {
-                req = elv_next_request(host->breq);
-                if (req)
-                        name = req->rq_disk->disk_name;
-        }
+        if (host->req)
+                name = host->req->rq_disk->disk_name;
 
         printk(KERN_ERR "%s: %s: status=0x%02x { ", name, msg, stat & 0xff);
         if (stat & ATA_BUSY)
@@ -217,13 +228,9 @@ static void mg_dump_status(const char *msg, unsigned int stat,
                         printk("AddrMarkNotFound ");
                 printk("}");
                 if (host->error & (ATA_BBK | ATA_UNC | ATA_IDNF | ATA_AMNF)) {
-                        if (host->breq) {
-                                req = elv_next_request(host->breq);
-                                if (req)
-                                        printk(", sector=%u",
-                                               (unsigned int)blk_rq_pos(req));
-                        }
-
+                        if (host->req)
+                                printk(", sector=%u",
+                                       (unsigned int)blk_rq_pos(host->req));
                 }
                 printk("\n");
         }
@@ -453,11 +460,10 @@ static int mg_disk_init(struct mg_host *host)
 
 static void mg_bad_rw_intr(struct mg_host *host)
 {
-        struct request *req = elv_next_request(host->breq);
-        if (req != NULL)
-                if (++req->errors >= MG_MAX_ERRORS ||
-                                host->error == MG_ERR_TIMEOUT)
-                        __blk_end_request_cur(req, -EIO);
+        if (host->req)
+                if (++host->req->errors >= MG_MAX_ERRORS ||
+                    host->error == MG_ERR_TIMEOUT)
+                        mg_end_request_cur(host, -EIO);
 }
 
 static unsigned int mg_out(struct mg_host *host,
@@ -515,7 +521,7 @@ static void mg_read(struct request *req)
 
                 outb(MG_CMD_RD_CONF, (unsigned long)host->dev_base +
                                 MG_REG_COMMAND);
-        } while (__blk_end_request(req, 0, MG_SECTOR_SIZE));
+        } while (mg_end_request(host, 0, MG_SECTOR_SIZE));
 }
 
 static void mg_write(struct request *req)
@@ -545,14 +551,14 @@ static void mg_write(struct request *req)
 
                 outb(MG_CMD_WR_CONF, (unsigned long)host->dev_base +
                                 MG_REG_COMMAND);
-        } while (__blk_end_request(req, 0, MG_SECTOR_SIZE));
+        } while (mg_end_request(host, 0, MG_SECTOR_SIZE));
 }
 
 static void mg_read_intr(struct mg_host *host)
 {
+        struct request *req = host->req;
         u32 i;
         u16 *buff;
-        struct request *req;
 
         /* check status */
         do {
@@ -571,7 +577,6 @@ static void mg_read_intr(struct mg_host *host)
 
 ok_to_read:
         /* get current segment of request */
-        req = elv_next_request(host->breq);
         buff = (u16 *)req->buffer;
 
         /* read 1 sector */
@@ -585,7 +590,7 @@ ok_to_read:
         /* send read confirm */
         outb(MG_CMD_RD_CONF, (unsigned long)host->dev_base + MG_REG_COMMAND);
 
-        if (__blk_end_request(req, 0, MG_SECTOR_SIZE)) {
+        if (mg_end_request(host, 0, MG_SECTOR_SIZE)) {
                 /* set handler if read remains */
                 host->mg_do_intr = mg_read_intr;
                 mod_timer(&host->timer, jiffies + 3 * HZ);
@@ -595,14 +600,11 @@ ok_to_read:
 
 static void mg_write_intr(struct mg_host *host)
 {
+        struct request *req = host->req;
         u32 i, j;
         u16 *buff;
-        struct request *req;
         bool rem;
 
-        /* get current segment of request */
-        req = elv_next_request(host->breq);
-
         /* check status */
         do {
                 i = inb((unsigned long)host->dev_base + MG_REG_STATUS);
@@ -619,7 +621,7 @@ static void mg_write_intr(struct mg_host *host)
         return;
 
 ok_to_write:
-        if ((rem = __blk_end_request(req, 0, MG_SECTOR_SIZE))) {
+        if ((rem = mg_end_request(host, 0, MG_SECTOR_SIZE))) {
                 /* write 1 sector and set handler if remains */
                 buff = (u16 *)req->buffer;
                 for (j = 0; j < MG_STORAGE_BUFFER_SIZE >> 1; j++) {
@@ -644,44 +646,47 @@ void mg_times_out(unsigned long data)
 {
         struct mg_host *host = (struct mg_host *)data;
         char *name;
-        struct request *req;
 
         spin_lock_irq(&host->lock);
 
-        req = elv_next_request(host->breq);
-        if (!req)
+        if (!host->req)
                 goto out_unlock;
 
         host->mg_do_intr = NULL;
 
-        name = req->rq_disk->disk_name;
+        name = host->req->rq_disk->disk_name;
         printk(KERN_DEBUG "%s: timeout\n", name);
 
         host->error = MG_ERR_TIMEOUT;
         mg_bad_rw_intr(host);
 
-        mg_request(host->breq);
 out_unlock:
+        mg_request(host->breq);
         spin_unlock_irq(&host->lock);
 }
 
 static void mg_request_poll(struct request_queue *q)
 {
-        struct request *req;
-        struct mg_host *host;
+        struct mg_host *host = q->queuedata;
 
-        while ((req = elv_next_request(q)) != NULL) {
-                host = req->rq_disk->private_data;
+        while (1) {
+                if (!host->req) {
+                        host->req = elv_next_request(q);
+                        if (host->req)
+                                blkdev_dequeue_request(host->req);
+                        else
+                                break;
+                }
 
-                if (unlikely(!blk_fs_request(req))) {
-                        __blk_end_request_cur(req, -EIO);
+                if (unlikely(!blk_fs_request(host->req))) {
+                        mg_end_request_cur(host, -EIO);
                         continue;
                 }
 
-                if (rq_data_dir(req) == READ)
-                        mg_read(req);
+                if (rq_data_dir(host->req) == READ)
+                        mg_read(host->req);
                 else
-                        mg_write(req);
+                        mg_write(host->req);
         }
 }
 
@@ -733,16 +738,19 @@ static unsigned int mg_issue_req(struct request *req,
 /* This function also called from IRQ context */
 static void mg_request(struct request_queue *q)
 {
+        struct mg_host *host = q->queuedata;
         struct request *req;
-        struct mg_host *host;
         u32 sect_num, sect_cnt;
 
         while (1) {
-                req = elv_next_request(q);
-                if (!req)
-                        return;
-
-                host = req->rq_disk->private_data;
+                if (!host->req) {
+                        host->req = elv_next_request(q);
+                        if (host->req)
+                                blkdev_dequeue_request(host->req);
+                        else
+                                break;
+                }
+                req = host->req;
 
                 /* check unwanted request call */
                 if (host->mg_do_intr)
@@ -762,12 +770,12 @@ static void mg_request(struct request_queue *q)
                                         "%s: bad access: sector=%d, count=%d\n",
                                         req->rq_disk->disk_name,
                                         sect_num, sect_cnt);
-                        __blk_end_request_cur(req, -EIO);
+                        mg_end_request_cur(host, -EIO);
                         continue;
                 }
 
                 if (unlikely(!blk_fs_request(req))) {
-                        __blk_end_request_cur(req, -EIO);
+                        mg_end_request_cur(host, -EIO);
                         continue;
                 }
 
@@ -981,6 +989,7 @@ static int mg_probe(struct platform_device *plat_dev)
                                 __func__, __LINE__);
                 goto probe_err_5;
         }
+        host->breq->queuedata = host;
 
         /* mflash is random device, thanx for the noop */
         elevator_exit(host->breq->elevator);