Re: [PATCH] bcache: fix unmatched generic_end_io_acct() & generic_start_io_acct()

[Coly Li <colyli@suse.de>]

On 03/01/2018 12:39 PM, Zhai Zhaoxuan wrote:
> The function cached_dev_make_request() and flash_dev_make_request() call
> generic_start_io_acct() with (struct bcache_device)->disk when they start a
> closure. Then the function bio_complete() calls generic_end_io_acct() with
> (struct search)->orig_bio->bi_disk when the closure has done.
> Since the `bi_disk` is not the bcache device, the generic_end_io_acct() is
> called with a wrong device queue.
> 
> It causes the "inflight" (in struct hd_struct) counter keep increasing
> without decreasing.
> 
> This patch fix the problem by calling generic_end_io_acct() with
> (struct bcache_device)->disk.
> 
> Signed-off-by: Zhai Zhaoxuan <kxuanobj@gmail.com>

Hi Zhaoxuan,

Nice catch, it makes sense. Thanks.

Reviewed-by: Coly Li <colyli@suse.de>

One more question, do you experience any problem when inflight counter
increases only ? I just wondering.

Coly

> ---
>  drivers/md/bcache/request.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index 643c3021624f..83de85fe4542 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -611,8 +611,8 @@ static void request_endio(struct bio *bio)
>  static void bio_complete(struct search *s)
>  {
>  	if (s->orig_bio) {
> -		struct request_queue *q = s->orig_bio->bi_disk->queue;
> -		generic_end_io_acct(q, bio_data_dir(s->orig_bio),
> +		generic_end_io_acct(s->d->disk->queue,
> +				    bio_data_dir(s->orig_bio),
>  				    &s->d->disk->part0, s->start_time);
>  
>  		trace_bcache_request_end(s->d, s->orig_bio);
>