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scsi: iscsi: Remove unneeded task state check 

Commit 5923d64b7a ("scsi: libiscsi: Drop taskqueuelock") added an extra
task->state because for commit 6f8830f5bb ("scsi: libiscsi: add lock
around task lists to fix list corruption regression") we didn't know why we
ended up with cmds on the list and thought it might have been a bad target
sending a response while we were still sending the cmd. We were never able
to get a target to send us a response early, because it turns out the bug
was just a race in libiscsi/libiscsi_tcp where:

 1. iscsi_tcp_r2t_rsp() queues a r2t to tcp_task->r2tqueue.

 2. iscsi_tcp_task_xmit() runs iscsi_tcp_get_curr_r2t() and sees we have a
    r2t. It dequeues it and iscsi_tcp_task_xmit() starts to process it.

 3. iscsi_tcp_r2t_rsp() runs iscsi_requeue_task() and puts the task on the
    requeue list.

 4. iscsi_tcp_task_xmit() sends the data for r2t. This is the final chunk
    of data, so the cmd is done.

 5. target sends the response.

 6. On a different CPU from #3, iscsi_complete_task() processes the
    response.  Since there was no common lock for the list, the lists/tasks
    pointers are not fully in sync, so could end up with list corruption.

Since it was just a race on our side, remove the extra check and fix up the
comments.

Link: https://lore.kernel.org/r/20220616224557.115234-7-michael.christie@oracle.com
Reviewed-by: Wu Bo <wubo40@huawei.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Mike Christie 2022-06-16 17:45:54 -05:00 committed by Martin K. Petersen
parent 9b89153680
commit 533ac412fd
1 changed files with 8 additions and 5 deletions
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13
drivers/scsi/libiscsi.c
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@ -567,16 +567,19 @@ static bool cleanup_queued_task(struct iscsi_task *task)
struct iscsi_conn *conn = task->conn;
bool early_complete = false;
/* Bad target might have completed task while it was still running */
/*
* We might have raced where we handled a R2T early and got a response
* but have not yet taken the task off the requeue list, then a TMF or
* recovery happened and so we can still see it here.
*/
if (task->state == ISCSI_TASK_COMPLETED)
early_complete = true;
if (!list_empty(&task->running)) {
list_del_init(&task->running);
/*
* If it's on a list but still running, this could be from
* a bad target sending a rsp early, cleanup from a TMF, or
* session recovery.
* If it's on a list but still running this could be cleanup
* from a TMF or session recovery.
*/
if (task->state == ISCSI_TASK_RUNNING ||
task->state == ISCSI_TASK_COMPLETED)
@ -1485,7 +1488,7 @@ static int iscsi_xmit_task(struct iscsi_conn *conn, struct iscsi_task *task,
}
/* regular RX path uses back_lock */
spin_lock(&conn->session->back_lock);
if (rc && task->state == ISCSI_TASK_RUNNING) {
if (rc) {
/*
* get an extra ref that is released next time we access it
* as conn->task above.