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Code

bcache: fix inaccurate io state for detached bcache devices

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When we run IO in a detached device,  and run iostat to shows IO status,
normally it will show like bellow (Omitted some fields):
Device: ... avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
sdd        ... 15.89     0.53    1.82    0.20    2.23   1.81  52.30
bcache0    ... 15.89   115.42    0.00    0.00    0.00   2.40  69.60
but after IO stopped, there are still very big avgqu-sz and %util
values as bellow:
Device: ... avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
bcache0   ...      0   5326.32    0.00    0.00    0.00   0.00 100.10

The reason for this issue is that, only generic_start_io_acct() called
and no generic_end_io_acct() called for detached device in
cached_dev_make_request(). See the code:
//start generic_start_io_acct()
generic_start_io_acct(q, rw, bio_sectors(bio), &d->disk->part0);
if (cached_dev_get(dc)) {
	//will callback generic_end_io_acct()
}
else {
	//will not call generic_end_io_acct()
}

This patch calls generic_end_io_acct() in the end of IO for detached
devices, so we can show IO state correctly.

(Modified to use GFP_NOIO in kzalloc() by Coly Li)

Changelog:
v2: fix typo.
v1: the initial version.

Signed-off-by: Tang Junhui <tang.junhui@zte.com.cn>
Reviewed-by: Coly Li <colyli@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Michael Lyle <mlyle@lyle.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tang Junhui 2018-03-18 17:36:19 -07:00 committed by Jens Axboe
parent 7e027ca4b5
commit bc082a55d2
1 changed files with 51 additions and 7 deletions
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58
drivers/md/bcache/request.c
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@ -986,6 +986,55 @@ static void cached_dev_nodata(struct closure *cl)
continue_at(cl, cached_dev_bio_complete, NULL);
}
struct detached_dev_io_private {
struct bcache_device *d;
unsigned long start_time;
bio_end_io_t *bi_end_io;
void *bi_private;
};
static void detached_dev_end_io(struct bio *bio)
{
struct detached_dev_io_private *ddip;
ddip = bio->bi_private;
bio->bi_end_io = ddip->bi_end_io;
bio->bi_private = ddip->bi_private;
generic_end_io_acct(ddip->d->disk->queue,
bio_data_dir(bio),
&ddip->d->disk->part0, ddip->start_time);
kfree(ddip);
bio->bi_end_io(bio);
}
static void detached_dev_do_request(struct bcache_device *d, struct bio *bio)
{
struct detached_dev_io_private *ddip;
struct cached_dev *dc = container_of(d, struct cached_dev, disk);
/*
* no need to call closure_get(&dc->disk.cl),
* because upper layer had already opened bcache device,
* which would call closure_get(&dc->disk.cl)
*/
ddip = kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO);
ddip->d = d;
ddip->start_time = jiffies;
ddip->bi_end_io = bio->bi_end_io;
ddip->bi_private = bio->bi_private;
bio->bi_end_io = detached_dev_end_io;
bio->bi_private = ddip;
if ((bio_op(bio) == REQ_OP_DISCARD) &&
!blk_queue_discard(bdev_get_queue(dc->bdev)))
bio->bi_end_io(bio);
else
generic_make_request(bio);
}
/* Cached devices - read & write stuff */
static blk_qc_t cached_dev_make_request(struct request_queue *q,
@ -1028,13 +1077,8 @@ static blk_qc_t cached_dev_make_request(struct request_queue *q,
else
cached_dev_read(dc, s);
}
} else {
if ((bio_op(bio) == REQ_OP_DISCARD) &&
!blk_queue_discard(bdev_get_queue(dc->bdev)))
bio_endio(bio);
else
generic_make_request(bio);
}
} else
detached_dev_do_request(d, bio);
return BLK_QC_T_NONE;
}