This is a note to let you know that I've just added the patch titled bcache: fix bio_{start,end}_io_acct with proper device to the 5.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bcache-fix-bio_-start-end-_io_acct-with-proper-device.patch and it can be found in the queue-5.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From a2f32ee8fd853cec8860f883d98afc3a339546de Mon Sep 17 00:00:00 2001 From: Coly Li <colyli@xxxxxxx> Date: Sat, 25 Jul 2020 20:00:39 +0800 Subject: bcache: fix bio_{start,end}_io_acct with proper device From: Coly Li <colyli@xxxxxxx> commit a2f32ee8fd853cec8860f883d98afc3a339546de upstream. Commit 85750aeb748f ("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: 85750aeb748f ("bcache: use bio_{start,end}_io_acct") Signed-off-by: Coly Li <colyli@xxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/bcache/request.c | 31 +++++++++++++++++++++++++++---- 1 file changed, 27 insertions(+), 4 deletions(-) --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -617,6 +617,28 @@ static void cache_lookup(struct closure /* 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 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_allo 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 b 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(stru */ 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; Patches currently in stable-queue which might be from colyli@xxxxxxx are queue-5.8/bcache-fix-overflow-in-offset_to_stripe.patch queue-5.8/bcache-use-disk_-start-end-_io_acct-to-count-i-o-for-bcache-device.patch queue-5.8/bcache-avoid-nr_stripes-overflow-in-bcache_device_init.patch queue-5.8/bcache-fix-bio_-start-end-_io_acct-with-proper-device.patch queue-5.8/bcache-allocate-meta-data-pages-as-compound-pages.patch