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

Sergei Shtylyov
2009-05-16T12:55:31Z

Hello.

Tejun Heo wrote:

> 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@kernel.org>
> ---
> 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);

+ blkdev_dequeue_request(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);
+ done:
+ if (__blk_end_request_cur(req, err));
+ break;
}
}

MBR, Sergei