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>

diff --git a/drivers/block/mg_disk.c b/drivers/block/mg_disk.c
index be32388..1ca5d14 100644 (file)
--- 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);