Re: Panic when rebooting target server testing srp on 5.0.0-rc2

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On Wed, 2019-03-27 at 18:00 -0400, Laurence Oberman wrote:
+AD4 Hello Jens, Jianchao
+AD4 Finally made it to this one.
+AD4 I will see if I can revert and test
+AD4 
+AD4 7f556a44e61d0b62d78db9a2662a5f0daef010f2 is the first bad commit
+AD4 commit 7f556a44e61d0b62d78db9a2662a5f0daef010f2
+AD4 Author: Jianchao Wang +ADw-jianchao.w.wang+AEA-oracle.com+AD4
+AD4 Date:   Fri Dec 14 09:28:18 2018 +-0800
+AD4 
+AD4     blk-mq: refactor the code of issue request directly
+AD4     
+AD4     Merge blk+AF8-mq+AF8-try+AF8-issue+AF8-directly and +AF8AXw-blk+AF8-mq+AF8-try+AF8-issue+AF8-directly
+AD4     into one interface to unify the interfaces to issue requests
+AD4     directly. The merged interface takes over the requests totally,
+AD4     it could insert, end or do nothing based on the return value of
+AD4     .queue+AF8-rq and 'bypass' parameter. Then caller needn't any other
+AD4     handling any more and then code could be cleaned up.
+AD4     
+AD4     And also the commit c616cbee ( blk-mq: punt failed direct issue
+AD4     to dispatch list ) always inserts requests to hctx dispatch list
+AD4     whenever get a BLK+AF8-STS+AF8-RESOURCE or BLK+AF8-STS+AF8-DEV+AF8-RESOURCE, this is
+AD4     overkill and will harm the merging. We just need to do that for
+AD4     the requests that has been through .queue+AF8-rq. This patch also
+AD4     could fix this.
+AD4     
+AD4     Signed-off-by: Jianchao Wang +ADw-jianchao.w.wang+AEA-oracle.com+AD4
+AD4     Signed-off-by: Jens Axboe +ADw-axboe+AEA-kernel.dk+AD4

Hi Laurence,

I have not been able to reproduce this issue. But you may want to try
the following patch (applies on top of v5.1-rc3):


Subject: +AFs-PATCH+AF0 block: Fix blk+AF8-mq+AF8-try+AF8-issue+AF8-directly()

If blk+AF8-mq+AF8-try+AF8-issue+AF8-directly() returns BLK+AF8-STS+ACoAXw-RESOURCE that means that
the request has not been queued and that the caller should retry to submit
the request. Both blk+AF8-mq+AF8-request+AF8-bypass+AF8-insert() and
blk+AF8-mq+AF8-sched+AF8-insert+AF8-request() guarantee that a request will be processed.
Hence return BLK+AF8-STS+AF8-OK if one of these functions is called. This patch
avoids that blk+AF8-mq+AF8-dispatch+AF8-rq+AF8-list() crashes when using dm-mpath.

Reported-by: Laurence Oberman +ADw-loberman+AEA-redhat.com+AD4
Fixes: 7f556a44e61d (+ACI-blk-mq: refactor the code of issue request directly+ACI) +ACM v5.0.
Signed-off-by: Bart Van Assche +ADw-bvanassche+AEA-acm.org+AD4
---
 block/blk-mq.c +AHw 9 +-+--------
 1 file changed, 2 insertions(+-), 7 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 652d0c6d5945..b2c20dce8a30 100644
--- a/block/blk-mq.c
+-+-+- b/block/blk-mq.c
+AEAAQA -1859,16 +-1859,11 +AEAAQA blk+AF8-status+AF8-t blk+AF8-mq+AF8-try+AF8-issue+AF8-directly(struct blk+AF8-mq+AF8-hw+AF8-ctx +ACo-hctx,
 	case BLK+AF8-STS+AF8-RESOURCE:
 		if (force) +AHs
 			blk+AF8-mq+AF8-request+AF8-bypass+AF8-insert(rq, run+AF8-queue)+ADs
-			/+ACo
-			 +ACo We have to return BLK+AF8-STS+AF8-OK for the DM
-			 +ACo to avoid livelock. Otherwise, we return
-			 +ACo the real result to indicate whether the
-			 +ACo request is direct-issued successfully.
-			 +ACo-/
-			ret +AD0 bypass ? BLK+AF8-STS+AF8-OK : ret+ADs
+-			ret +AD0 BLK+AF8-STS+AF8-OK+ADs
 		+AH0 else if (+ACE-bypass) +AHs
 			blk+AF8-mq+AF8-sched+AF8-insert+AF8-request(rq, false,
 						    run+AF8-queue, false)+ADs
+-			ret +AD0 BLK+AF8-STS+AF8-OK+ADs
 		+AH0
 		break+ADs
 	default:


Thanks,

Bart.



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