diff options
Diffstat (limited to 'Documentation/scsi/scsi_eh.rst')
| -rw-r--r-- | Documentation/scsi/scsi_eh.rst | 71 |
1 files changed, 22 insertions, 49 deletions
diff --git a/Documentation/scsi/scsi_eh.rst b/Documentation/scsi/scsi_eh.rst index 7d78c2475615..36cff176c5e6 100644 --- a/Documentation/scsi/scsi_eh.rst +++ b/Documentation/scsi/scsi_eh.rst @@ -54,13 +54,13 @@ invoking hostt->queuecommand() or the block layer will time it out. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ For all non-EH commands, scsi_done() is the completion callback. It -just calls blk_complete_request() to delete the block layer timer and -raise SCSI_SOFTIRQ +just calls blk_mq_complete_request() to delete the block layer timer and +raise BLOCK_SOFTIRQ. -SCSI_SOFTIRQ handler scsi_softirq calls scsi_decide_disposition() to -determine what to do with the command. scsi_decide_disposition() -looks at the scmd->result value and sense data to determine what to do -with the command. +The BLOCK_SOFTIRQ indirectly calls scsi_complete(), which calls +scsi_decide_disposition() to determine what to do with the command. +scsi_decide_disposition() looks at the scmd->result value and sense +data to determine what to do with the command. - SUCCESS @@ -87,29 +87,30 @@ with the command. 1.2.2 Completing a scmd w/ timeout ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -The timeout handler is scsi_times_out(). When a timeout occurs, this -function +The timeout handler is scsi_timeout(). When a timeout occurs, this function 1. invokes optional hostt->eh_timed_out() callback. Return value can be one of - - BLK_EH_RESET_TIMER + - SCSI_EH_RESET_TIMER This indicates that more time is required to finish the - command. Timer is restarted. This action is counted as a - retry and only allowed scmd->allowed + 1(!) times. Once the - limit is reached, action for BLK_EH_DONE is taken instead. + command. Timer is restarted. - - BLK_EH_DONE + - SCSI_EH_NOT_HANDLED eh_timed_out() callback did not handle the command. Step #2 is taken. - 2. scsi_abort_command() is invoked to schedule an asynchrous abort. - Asynchronous abort are not invoked for commands which the - SCSI_EH_ABORT_SCHEDULED flag is set (this indicates that the command - already had been aborted once, and this is a retry which failed), - or when the EH deadline is expired. In these case Step #3 is taken. + - SCSI_EH_DONE + eh_timed_out() completed the command. - 3. scsi_eh_scmd_add(scmd, SCSI_EH_CANCEL_CMD) is invoked for the + 2. scsi_abort_command() is invoked to schedule an asynchronous abort which may + issue a retry scmd->allowed + 1 times. Asynchronous aborts are not invoked + for commands for which the SCSI_EH_ABORT_SCHEDULED flag is set (this + indicates that the command already had been aborted once, and this is a + retry which failed), when retries are exceeded, or when the EH deadline is + expired. In these cases Step #3 is taken. + + 3. scsi_eh_scmd_add(scmd) is invoked for the command. See [1-4] for more information. 1.3 Asynchronous command aborts @@ -276,7 +277,6 @@ scmd->allowed. :ACTION: scsi_eh_finish_cmd() is invoked to EH-finish scmd - - scsi_setup_cmd_retry() - move from local eh_work_q to local eh_done_q :LOCKING: none @@ -316,7 +316,7 @@ scmd->allowed. ``scsi_eh_get_sense`` This action is taken for each error-completed - (!SCSI_EH_CANCEL_CMD) commands without valid sense data. Most + command without valid sense data. Most SCSI transports/LLDDs automatically acquire sense data on command failures (autosense). Autosense is recommended for performance reasons and as sense information could get out of @@ -346,30 +346,6 @@ scmd->allowed. - otherwise No action. - 3. If !list_empty(&eh_work_q), invoke scsi_eh_abort_cmds(). - - ``scsi_eh_abort_cmds`` - - This action is taken for each timed out command when - no_async_abort is enabled in the host template. - hostt->eh_abort_handler() is invoked for each scmd. The - handler returns SUCCESS if it has succeeded to make LLDD and - all related hardware forget about the scmd. - - If a timedout scmd is successfully aborted and the sdev is - either offline or ready, scsi_eh_finish_cmd() is invoked for - the scmd. Otherwise, the scmd is left in eh_work_q for - higher-severity actions. - - Note that both offline and ready status mean that the sdev is - ready to process new scmds, where processing also implies - immediate failing; thus, if a sdev is in one of the two - states, no further recovery action is needed. - - Device readiness is tested using scsi_eh_tur() which issues - TEST_UNIT_READY command. Note that the scmd must have been - aborted successfully before reusing it for TEST_UNIT_READY. - 4. If !list_empty(&eh_work_q), invoke scsi_eh_ready_devs() ``scsi_eh_ready_devs`` @@ -383,7 +359,7 @@ scmd->allowed. For each sdev which has failed scmds with valid sense data of which scsi_check_sense()'s verdict is FAILED, - START_STOP_UNIT command is issued w/ start=1. Note that + START STOP UNIT command is issued w/ start=1. Note that as we explicitly choose error-completed scmds, it is known that lower layers have forgotten about the scmd and we can reuse it for STU. @@ -477,9 +453,6 @@ except for #1 must be implemented by eh_strategy_handler(). - shost->host_failed is zero. - - Each scmd is in such a state that scsi_setup_cmd_retry() on the - scmd doesn't make any difference. - - shost->eh_cmd_q is cleared. - Each scmd->eh_entry is cleared. |