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Message-ID: <4A0F1AE3.5080105@ru.mvista.com>
Date: Sat, 16 May 2009 23:58:27 +0400
From: Sergei Shtylyov <sshtylyov@...mvista.com>
To: Sergei Shtylyov <sshtylyov@...mvista.com>
Cc: Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
linux-scsi@...r.kernel.org, linux-ide@...r.kernel.org,
rusty@...tcorp.com.au, James.Bottomley@...senPartnership.com,
mike.miller@...com, donari75@...il.com, paul.clements@...eleye.com,
tim@...erelk.net, Geert.Uytterhoeven@...ycom.com,
davem@...emloft.net, Laurent@...vier.info, jgarzik@...ox.com,
jeremy@...source.com, grant.likely@...retlab.ca,
adrian@...en.demon.co.uk, sfr@...b.auug.org.au, bzolnier@...il.com,
petkovbb@...glemail.com, oakad@...oo.com, drzeus@...eus.cx,
dwmw2@...radead.org, Markus.Lidel@...dowconnect.com,
wein@...ibm.com, schwidefsky@...ibm.com, zaitcev@...hat.com,
fujita.tomonori@....ntt.co.jp, axboe@...nel.dk
Subject: Re: [PATCH 15/18] z2ram: dequeue in-flight request
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@...nel.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);
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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