On 9/18/20 4:09 PM, Lee Duncan wrote:
From: Lee Duncan <lduncan@xxxxxxxx>
iSCSI NOPs are sometimes "lost", mistakenly sent to the
user-land iscsid daemon instead of handled in the kernel,
as they should be, resulting in a message from the daemon like:
iscsid: Got nop in, but kernel supports nop handling.
This can occur because of the new forward- and back-locks,
and the fact that an iSCSI NOP response can occur before
processing of the NOP send is complete. This can result
in "conn->ping_task" being NULL in iscsi_nop_out_rsp(),
when the pointer is actually in the process of being set.
To work around this, we add a new state to the "ping_task"
pointer. In addition to NULL (not assigned) and a pointer
(assigned), we add the state "being set", which is signaled
with an INVALID pointer (using "-1").
Signed-off-by: Lee Duncan <lduncan@xxxxxxxx>
---
drivers/scsi/libiscsi.c | 11 ++++++++++-
include/scsi/libiscsi.h | 3 +++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 1e9c3171fa9f..5eb064787ee2 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -738,6 +738,9 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
task->conn->session->age);
}
+ if (unlikely(READ_ONCE(conn->ping_task) == INVALID_SCSI_TASK))
+ WRITE_ONCE(conn->ping_task, task);
+
if (!ihost->workq) {
if (iscsi_prep_mgmt_task(conn, task))
goto free_task;
@@ -941,6 +944,11 @@ static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
struct iscsi_nopout hdr;
struct iscsi_task *task;
+ if (!rhdr) {
+ if (READ_ONCE(conn->ping_task))
+ return -EINVAL;
+ WRITE_ONCE(conn->ping_task, INVALID_SCSI_TASK);
+ }
if (!rhdr && conn->ping_task)
return -EINVAL;
@@ -957,11 +965,12 @@ static int iscsi_send_nopout(struct iscsi_conn *conn, struct iscsi_nopin *rhdr)
task = __iscsi_conn_send_pdu(conn, (struct iscsi_hdr *)&hdr, NULL, 0);
if (!task) {
+ if (!rhdr)
+ WRITE_ONCE(conn->ping_task, NULL);
I don't think you need this. If __iscsi_conn_send_pdu returns NULL, it
will have done __iscsi_put_task and done this already.
iscsi_conn_printk(KERN_ERR, conn, "Could not send nopout\n");
return -EIO;
} else if (!rhdr) {
/* only track our nops */
- conn->ping_task = task;
conn->last_ping = jiffies;
}
Why in the send path do we always use the READ_ONCE/WRITE_ONCE, but in
the completion path like in iscsi_complete_task we don't.
