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Commit bc082a55 authored by Tang Junhui's avatar Tang Junhui Committed by Jens Axboe
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bcache: fix inaccurate io state for detached bcache devices 



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: default avatarTang Junhui <tang.junhui@zte.com.cn>
Reviewed-by: default avatarColy Li <colyli@suse.de>
Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Reviewed-by: default avatarMichael Lyle <mlyle@lyle.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 7e027ca4

drivers/md/bcache/request.c

+51 −7
Original line number Diff line number Diff line
@@ -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;

}