From 533ac412fdb4cbc8ce282b1ee1991e03b2717625 Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Thu, 16 Jun 2022 17:45:54 -0500 Subject: scsi: iscsi: Remove unneeded task state check Commit 5923d64b7ab6 ("scsi: libiscsi: Drop taskqueuelock") added an extra task->state because for commit 6f8830f5bbab ("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 Reviewed-by: Lee Duncan Signed-off-by: Mike Christie Signed-off-by: Martin K. Petersen --- drivers/scsi/libiscsi.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) (limited to 'drivers') diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c index 20156fb33646..fce9f9e5b00b 100644 --- a/drivers/scsi/libiscsi.c +++ b/drivers/scsi/libiscsi.c @@ -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. -- cgit v1.2.3