On 9/17/19 6:09 AM, Jinpu Wang wrote:
+static void ibnbd_softirq_done_fn(struct request *rq)
+{
+ struct ibnbd_clt_dev *dev = rq->rq_disk->private_data;
+ struct ibnbd_clt_session *sess = dev->sess;
+ struct ibnbd_iu *iu;
+
+ iu = blk_mq_rq_to_pdu(rq);
+ ibnbd_put_tag(sess, iu->tag);
+ blk_mq_end_request(rq, iu->status);
+}
+
+static void msg_io_conf(void *priv, int errno)
+{
+ struct ibnbd_iu *iu = (struct ibnbd_iu *)priv;
+ struct ibnbd_clt_dev *dev = iu->dev;
+ struct request *rq = iu->rq;
+
+ iu->status = errno ? BLK_STS_IOERR : BLK_STS_OK;
+
+ if (softirq_enable) {
+ blk_mq_complete_request(rq);
+ } else {
+ ibnbd_put_tag(dev->sess, iu->tag);
+ blk_mq_end_request(rq, iu->status);
+ }
Block drivers must call blk_mq_complete_request() instead of
blk_mq_end_request() to complete a request after processing of the
request has been started. Calling blk_mq_end_request() to complete a
request is racy in case a timeout occurs while blk_mq_end_request() is
in progress.
Could you elaborate a bit more, blk_mq_end_request is exported function and
used by a lot of block drivers: scsi, dm, etc.
Is there an open bug report for the problem?
Hi Jinpu,
There is only one blk_mq_end_request() call in the SCSI code and it's
inside the FC timeout handler (fc_bsg_job_timeout()). Calling
blk_mq_end_request() from inside a timeout handler is fine but not to
report to the block layer that a request has completed from outside the
timeout handler after a request has started.
The device mapper calls blk_mq_complete_request() to report request
completion to the block layer. See also dm_complete_request().
blk_mq_end_request() is only called by the device mapper from inside
dm_softirq_done(). That last function is called from inside
blk_mq_complete_request() and is not called directly.
The NVMe PCIe driver only calls blk_mq_end_request() from inside
nvme_complete_rq(). nvme_complete_rq() is called by the PCIe driver from
inside nvme_pci_complete_rq() and that last function is called from
inside blk_mq_complete_request().
In other words, the SCSI core, the device mapper and the NVMe PCIe
driver all use blk_mq_complete_request() to report request completion to
the block layer from outside timeout handlers after a request has been
started.
This is not a new requirement. I think that the legacy block layer
equivalent, blk_complete_request(), was introduced in 2006 and that
since then block drivers are required to call blk_complete_request() to
report completion of requests from outside a timeout handler after these
have been started.
Bart.
