Re: [PATCH -next v3 3/6] nbd: don't clear 'NBD_CMD_INFLIGHT' flag if request is not completed

Josef Bacik
2022-05-23T14:12:58Z

On Sat, May 21, 2022 at 03:37:46PM +0800, Yu Kuai wrote:
> Otherwise io will hung because request will only be completed if the
> cmd has the flag 'NBD_CMD_INFLIGHT'.
>
> Fixes: 07175cb1baf4 ("nbd: make sure request completion won't concurrent")
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
> drivers/block/nbd.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 2ee1e376d5c4..a0d0910dae2a 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -403,13 +403,14 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
> if (!mutex_trylock(&cmd->lock))
> return BLK_EH_RESET_TIMER;
>
> - if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
> + if (!test_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
> mutex_unlock(&cmd->lock);
> return BLK_EH_DONE;
> }
>
> if (!refcount_inc_not_zero(&nbd->config_refs)) {
> cmd->status = BLK_STS_TIMEOUT;
> + __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
> mutex_unlock(&cmd->lock);
> goto done;
> }
> @@ -478,6 +479,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
> dev_err_ratelimited(nbd_to_dev(nbd), "Connection timed out\n");
> set_bit(NBD_RT_TIMEDOUT, &config->runtime_flags);
> cmd->status = BLK_STS_IOERR;
> + __clear_bit(NBD_CMD_INFLIGHT, &cmd->flags);
> mutex_unlock(&cmd->lock);
> sock_shutdown(nbd);
> nbd_config_put(nbd);
> @@ -745,7 +747,7 @@ static struct nbd_cmd *nbd_handle_reply(struct nbd_device *nbd, int index,
> cmd = blk_mq_rq_to_pdu(req);
>
> mutex_lock(&cmd->lock);
> - if (!__test_and_clear_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
> + if (!test_bit(NBD_CMD_INFLIGHT, &cmd->flags)) {
> dev_err(disk_to_dev(nbd->disk), "Suspicious reply %d (status %u flags %lu)",
> tag, cmd->status, cmd->flags);
> ret = -ENOENT;
> @@ -854,8 +856,16 @@ static void recv_work(struct work_struct *work)
> }
>
> rq = blk_mq_rq_from_pdu(cmd);
> - if (likely(!blk_should_fake_timeout(rq->q)))
> - blk_mq_complete_request(rq);
> + if (likely(!blk_should_fake_timeout(rq->q))) {
> + bool complete;
> +
> + mutex_lock(&cmd->lock);
> + complete = __test_and_clear_bit(NBD_CMD_INFLIGHT,
> + &cmd->flags);
> + mutex_unlock(&cmd->lock);
> + if (complete)
> + blk_mq_complete_request(rq);
> + }

I'd rather this be handled in nbd_handle_reply. We should return with it
cleared if it's ready to be completed. Thanks,

Josef