Commit a2f32ee8 authored by Coly Li's avatar Coly Li Committed by Jens Axboe
Browse files

bcache: fix bio_{start,end}_io_acct with proper device 



Commit 85750aeb ("bcache: use bio_{start,end}_io_acct") moves the
io account code to the location after bio_set_dev(bio, dc->bdev) in
cached_dev_make_request(). Then the account is performed incorrectly on
backing device, indeed the I/O should be counted to bcache device like
/dev/bcache0.

With the mistaken I/O account, iostat does not display I/O counts for
bcache device and all the numbers go to backing device. In writeback
mode, the hard drive may have 340K+ IOPS which is impossible and wrong
for spinning disk.

This patch introduces bch_bio_start_io_acct() and bch_bio_end_io_acct(),
which switches bio->bi_disk to bcache device before calling
bio_start_io_acct() or bio_end_io_acct(). Now the I/Os are counted to
bcache device, and bcache device, cache device and backing device have
their correct I/O count information back.

Fixes: 85750aeb ("bcache: use bio_{start,end}_io_acct")
Signed-off-by: default avatarColy Li <colyli@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4e4d4e09

drivers/md/bcache/request.c

+27 −4
Original line number Diff line number Diff line
@@ -617,6 +617,28 @@ static void cache_lookup(struct closure *cl) 


/* Common code for the make_request functions */



static inline void bch_bio_start_io_acct(struct gendisk *acct_bi_disk,

					 struct bio *bio,

					 unsigned long *start_time)

{

	struct gendisk *saved_bi_disk = bio->bi_disk;



	bio->bi_disk = acct_bi_disk;

	*start_time = bio_start_io_acct(bio);

	bio->bi_disk = saved_bi_disk;

}



static inline void bch_bio_end_io_acct(struct gendisk *acct_bi_disk,

				       struct bio *bio,

				       unsigned long start_time)

{

	struct gendisk *saved_bi_disk = bio->bi_disk;



	bio->bi_disk = acct_bi_disk;

	bio_end_io_acct(bio, start_time);

	bio->bi_disk = saved_bi_disk;

}



static void request_endio(struct bio *bio)

{

	struct closure *cl = bio->bi_private;
@@ -668,7 +690,7 @@ static void backing_request_endio(struct bio *bio) 
static void bio_complete(struct search *s)

{

	if (s->orig_bio) {

		bio_end_io_acct(s->orig_bio, s->start_time);

		bch_bio_end_io_acct(s->d->disk, s->orig_bio, s->start_time);

		trace_bcache_request_end(s->d, s->orig_bio);

		s->orig_bio->bi_status = s->iop.status;

		bio_endio(s->orig_bio);
@@ -728,7 +750,7 @@ static inline struct search *search_alloc(struct bio *bio, 
	s->recoverable		= 1;

	s->write		= op_is_write(bio_op(bio));

	s->read_dirty_data	= 0;

	s->start_time		= bio_start_io_acct(bio);

	bch_bio_start_io_acct(d->disk, bio, &s->start_time);



	s->iop.c		= d->c;

	s->iop.bio		= NULL;
@@ -1080,7 +1102,7 @@ static void detached_dev_end_io(struct bio *bio) 
	bio->bi_end_io = ddip->bi_end_io;

	bio->bi_private = ddip->bi_private;



	bio_end_io_acct(bio, ddip->start_time);

	bch_bio_end_io_acct(ddip->d->disk, bio, ddip->start_time);



	if (bio->bi_status) {

		struct cached_dev *dc = container_of(ddip->d,
@@ -1105,7 +1127,8 @@ static void detached_dev_do_request(struct bcache_device *d, struct bio *bio) 
	 */

	ddip = kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO);

	ddip->d = d;

	ddip->start_time = bio_start_io_acct(bio);

	bch_bio_start_io_acct(d->disk, bio, &ddip->start_time);



	ddip->bi_end_io = bio->bi_end_io;

	ddip->bi_private = bio->bi_private;

	bio->bi_end_io = detached_dev_end_io;

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