Re: [PATCH 15/18] z2ram: dequeue in-flight request

From: Sergei Shtylyov
Date: Sat May 16 2009 - 15:58:59 EST


Hello, I wrote:

Oops, sent this message only to Tejun before, so have to repost now...

z2ram processes requests one-by-one synchronously and can be easily
converted to dequeueing model. Convert it.

[ Impact: dequeue in-flight request ]

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
drivers/block/z2ram.c | 19 +++++++++++++++----
1 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/block/z2ram.c b/drivers/block/z2ram.c
index 6a13838..c909c1a 100644
--- a/drivers/block/z2ram.c
+++ b/drivers/block/z2ram.c
@@ -70,15 +70,21 @@ static struct gendisk *z2ram_gendisk;
static void do_z2_request(struct request_queue *q)
{
struct request *req;
- while ((req = elv_next_request(q)) != NULL) {
+
+ req = elv_next_request(q);
+ if (req)
+ blkdev_dequeue_request(req);
+
+ while (req) {
unsigned long start = blk_rq_pos(req) << 9;
unsigned long len = blk_rq_cur_bytes(req);
+ int err = 0;
if (start + len > z2ram_size) {
printk( KERN_ERR DEVICE_NAME ": bad access: block=%lu, count=%u\n",
blk_rq_pos(req), blk_rq_cur_sectors(req));
- __blk_end_request_cur(req, -EIO);
- continue;
+ err = -EIO;
+ goto done;
}
while (len) {
unsigned long addr = start & Z2RAM_CHUNKMASK;
@@ -93,7 +99,12 @@ static void do_z2_request(struct request_queue *q)
start += size;
len -= size;
}
- __blk_end_request_cur(req, 0);
+ done:
+ if (!__blk_end_request_cur(req, err)) {
+ req = elv_next_request(q);
+ if (req)
+ blkdev_dequeue_request(req);
+ }
}
}

I'm sure this can be made more compact and without duplication (in many other cases as well):

@@ -70,15 +70,21 @@ static struct gendisk *z2ram_gendisk;

static void do_z2_request(struct request_queue *q)
{
struct request *req;
+
while ((req = elv_next_request(q)) != NULL) {
unsigned long start = blk_rq_pos(req) << 9;
unsigned long len = blk_rq_cur_bytes(req);

Oops, missed:

+ int err;
+

+ blkdev_dequeue_request(req);
+

+again:

if (start + len > z2ram_size) {
printk( KERN_ERR DEVICE_NAME ": bad access: block=%lu, count=%u\n",
blk_rq_pos(req), blk_rq_cur_sectors(req));
- __blk_end_request_cur(req, -EIO);
- continue;
+ err = -EIO;
+ goto done;
}
while (len) {
unsigned long addr = start & Z2RAM_CHUNKMASK;
@@ -93,7 +99,12 @@ static void do_z2_request(struct request_queue *q)
start += size;
len -= size;
}
- __blk_end_request_cur(req, 0);
+ err = 0;
+ done:
+ if (__blk_end_request_cur(req, err));
+ break;

Oops, should've been:

+ if (__blk_end_request_cur(req, err))
+ goto again;

}
}

It can also be:

@@ -70,15 +70,21 @@ static struct gendisk *z2ram_gendisk;
static void do_z2_request(struct request_queue *q)
{
- struct request *req;
- while ((req = elv_next_request(q)) != NULL) {
+ while (1) {
+ struct request *req = elv_next_request(q);
+ unsigned long start, len;
+ int err;
+
+ if (req == NULL)
+ break;
+
+ blkdev_dequeue_request(req);
+
+again:
+ start = blk_rq_pos(req) << 9;
+ len = blk_rq_cur_bytes(req);

if (start + len > z2ram_size) {
printk( KERN_ERR DEVICE_NAME ": bad access: block=%lu, count=%u\n",
blk_rq_pos(req), blk_rq_cur_sectors(req));
- __blk_end_request_cur(req, -EIO);
- continue;
+ err = -EIO;
+ goto done;
}
while (len) {
unsigned long addr = start & Z2RAM_CHUNKMASK;
@@ -93,7 +99,12 @@ static void do_z2_request(struct request_queue *q)
start += size;
len -= size;
}
- __blk_end_request_cur(req, 0);
+ err = 0;
+ done:
+ if (__blk_end_request_cur(req, err))
+ goto again;
}
}


if you want to get rid of the assignement in the *while* statement...

MBR, Sergei


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