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Subject[PATCH 04/18] hd: dequeue and track in-flight request
Date
hd has at most single request in flight.  Till now, whenever it needs
to access the in-flight request it called elv_next_request(). This
patch makes hd track the in-flight request directly and dequeue it
when processing starts. The added complexity is minimal and this will
help future block layer changes.

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

Signed-off-by: Tejun Heo <tj@kernel.org>
---
drivers/block/hd.c | 63 +++++++++++++++++++++++++++++++++-------------------
1 files changed, 40 insertions(+), 23 deletions(-)
diff --git a/drivers/block/hd.c b/drivers/block/hd.c
index a3b3994..288ab63 100644
--- a/drivers/block/hd.c
+++ b/drivers/block/hd.c
@@ -98,10 +98,9 @@

static DEFINE_SPINLOCK(hd_lock);
static struct request_queue *hd_queue;
+static struct request *hd_req;

#define MAJOR_NR HD_MAJOR
-#define QUEUE (hd_queue)
-#define CURRENT elv_next_request(hd_queue)

#define TIMEOUT_VALUE (6*HZ)
#define HD_DELAY 0
@@ -195,11 +194,24 @@ static void __init hd_setup(char *str, int *ints)
NR_HD = hdind+1;
}

+static bool hd_end_request(int err, unsigned int bytes)
+{
+ if (__blk_end_request(hd_req, err, bytes))
+ return true;
+ hd_req = NULL;
+ return false;
+}
+
+static bool hd_end_request_cur(int err)
+{
+ return hd_end_request(err, blk_rq_cur_bytes(hd_req));
+}
+
static void dump_status(const char *msg, unsigned int stat)
{
char *name = "hd?";
- if (CURRENT)
- name = CURRENT->rq_disk->disk_name;
+ if (hd_req)
+ name = hd_req->rq_disk->disk_name;

#ifdef VERBOSE_ERRORS
printk("%s: %s: status=0x%02x { ", name, msg, stat & 0xff);
@@ -227,8 +239,8 @@ static void dump_status(const char *msg, unsigned int stat)
if (hd_error & (BBD_ERR|ECC_ERR|ID_ERR|MARK_ERR)) {
printk(", CHS=%d/%d/%d", (inb(HD_HCYL)<<8) + inb(HD_LCYL),
inb(HD_CURRENT) & 0xf, inb(HD_SECTOR));
- if (CURRENT)
- printk(", sector=%ld", blk_rq_pos(CURRENT));
+ if (hd_req)
+ printk(", sector=%ld", blk_rq_pos(hd_req));
}
printk("\n");
}
@@ -406,11 +418,12 @@ static void unexpected_hd_interrupt(void)
*/
static void bad_rw_intr(void)
{
- struct request *req = CURRENT;
+ struct request *req = hd_req;
+
if (req != NULL) {
struct hd_i_struct *disk = req->rq_disk->private_data;
if (++req->errors >= MAX_ERRORS || (hd_error & BBD_ERR)) {
- __blk_end_request_cur(req, -EIO);
+ hd_end_request_cur(-EIO);
disk->special_op = disk->recalibrate = 1;
} else if (req->errors % RESET_FREQ == 0)
reset = 1;
@@ -454,14 +467,14 @@ static void read_intr(void)
return;

ok_to_read:
- req = CURRENT;
+ req = hd_req;
insw(HD_DATA, req->buffer, 256);
#ifdef DEBUG
printk("%s: read: sector %ld, remaining = %u, buffer=%p\n",
req->rq_disk->disk_name, blk_rq_pos(req) + 1,
blk_rq_sectors(req) - 1, req->buffer+512);
#endif
- if (__blk_end_request(req, 0, 512)) {
+ if (hd_end_request(0, 512)) {
SET_HANDLER(&read_intr);
return;
}
@@ -475,7 +488,7 @@ ok_to_read:

static void write_intr(void)
{
- struct request *req = CURRENT;
+ struct request *req = hd_req;
int i;
int retries = 100000;

@@ -494,7 +507,7 @@ static void write_intr(void)
return;

ok_to_write:
- if (__blk_end_request(req, 0, 512)) {
+ if (hd_end_request(0, 512)) {
SET_HANDLER(&write_intr);
outsw(HD_DATA, req->buffer, 256);
return;
@@ -525,18 +538,18 @@ static void hd_times_out(unsigned long dummy)

do_hd = NULL;

- if (!CURRENT)
+ if (!hd_req)
return;

spin_lock_irq(hd_queue->queue_lock);
reset = 1;
- name = CURRENT->rq_disk->disk_name;
+ name = hd_req->rq_disk->disk_name;
printk("%s: timeout\n", name);
- if (++CURRENT->errors >= MAX_ERRORS) {
+ if (++hd_req->errors >= MAX_ERRORS) {
#ifdef DEBUG
printk("%s: too many errors\n", name);
#endif
- __blk_end_request_cur(CURRENT, -EIO);
+ hd_end_request_cur(-EIO);
}
hd_request();
spin_unlock_irq(hd_queue->queue_lock);
@@ -551,7 +564,7 @@ static int do_special_op(struct hd_i_struct *disk, struct request *req)
}
if (disk->head > 16) {
printk("%s: cannot handle device with more than 16 heads - giving up\n", req->rq_disk->disk_name);
- __blk_end_request_cur(req, -EIO);
+ hd_end_request_cur(-EIO);
}
disk->special_op = 0;
return 1;
@@ -578,11 +591,15 @@ static void hd_request(void)
repeat:
del_timer(&device_timer);

- req = CURRENT;
- if (!req) {
- do_hd = NULL;
- return;
+ if (!hd_req) {
+ hd_req = elv_next_request(hd_queue);
+ if (!hd_req) {
+ do_hd = NULL;
+ return;
+ }
+ blkdev_dequeue_request(hd_req);
}
+ req = hd_req;

if (reset) {
reset_hd();
@@ -595,7 +612,7 @@ repeat:
((block+nsect) > get_capacity(req->rq_disk))) {
printk("%s: bad access: block=%d, count=%d\n",
req->rq_disk->disk_name, block, nsect);
- __blk_end_request_cur(req, -EIO);
+ hd_end_request_cur(-EIO);
goto repeat;
}

@@ -635,7 +652,7 @@ repeat:
break;
default:
printk("unknown hd-command\n");
- __blk_end_request_cur(req, -EIO);
+ hd_end_request_cur(-EIO);
break;
}
}
--
1.6.0.2


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