On 09/01/2018 10:27 AM, tang.junhui@xxxxxxxxxx wrote:
> From: Tang Junhui <tang.junhui@xxxxxxxxxx>
>
> 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.
>
> Signed-off-by: Tang Junhui <tang.junhui@xxxxxxxxxx>
It looks good to me. Reviewed-by: Coly Li <colyli@xxxxxxx>
I also modify the backing device bi_end_io to catch I/O status in my
backing device failure patches, so I am thinking of pick this patch into
my device failure patch set, then Mike does not need to merge the conflict.
Coly Li
[code snipped]
