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From: Hannes Reinecke <hare@suse.de>
To: Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>
Cc: Keith Busch <keith.busch@wdc.com>,
	linux-nvme@lists.infradead.org, Keith Busch <kbusch@kernel.org>,
	Daniel Wagner <daniel.wagner@suse.de>
Subject: Re: [PATCHv3] nvme-mpath: delete disk after last connection
Date: Thu, 6 May 2021 10:42:59 +0200	[thread overview]
Message-ID: <96fbc678-a7e8-aaf3-5f15-8c866e683afe@suse.de> (raw)
In-Reply-To: <20210506074341.GC14615@lst.de>

On 5/6/21 9:43 AM, Christoph Hellwig wrote:
> On Tue, May 04, 2021 at 12:54:14PM -0700, Sagi Grimberg wrote:
>> Yes, I'm not sure I understand your comment Christoph. This addresses an
>> issue with mdraid where hot unplug+replug does not restore the device to
>> the raid group (pci and fabrics alike), where before multipath this used
>> to work.
>>
>> queue_if_no_path is a dm-multipath feature so I'm not entirely clear
>> what is the concern? mdraid on nvme (pci/fabrics) used to work a certain
>> way, with the introduction of nvme-mpath the behavior was broken (as far
>> as I understand from Hannes).
> 
> AFAIK that specific mdraid behavior is also fixed by the uevent patch
> he sent.
> 
It is most emphatically _NOT_.

These two patches are complementary.

To rephrase: with the current behaviour MD is completely hosed once one
NVMe-oF device get removed after ctrl_loss_tmo kicks in.

And _nothing_ will fix that except a system reboot.

_That_ is the issue this patch fixes.

The other patch for sending the uevent is just to tell MD that recovery
can start. But recovery _cannot_ start without this patch.

> 
> I really do not think we should change the mpath behaviors years after
> first adding it.
> 

But only because no-one ever tested MD on nvme-multipath.
It has been broken since day 1.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		        Kernel Storage Architect
hare@suse.de			               +49 911 74053 688
SUSE Software Solutions Germany GmbH, 90409 Nürnberg
GF: F. Imendörffer, HRB 36809 (AG Nürnberg)

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  reply	other threads:[~2021-05-06  8:43 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-01 12:04 [PATCHv3] nvme-mpath: delete disk after last connection Hannes Reinecke
2021-05-04  8:54 ` Christoph Hellwig
2021-05-04 13:40   ` Hannes Reinecke
2021-05-04 19:54     ` Sagi Grimberg
2021-05-05 15:26       ` Keith Busch
2021-05-05 16:15         ` Hannes Reinecke
2021-05-05 20:40           ` Sagi Grimberg
2021-05-06  2:50             ` Keith Busch
2021-05-06  6:13             ` Hannes Reinecke
2021-05-06  7:43       ` Christoph Hellwig
2021-05-06  8:42         ` Hannes Reinecke [this message]
2021-05-06  9:47           ` Sagi Grimberg
2021-05-06 12:08             ` Christoph Hellwig
2021-05-06 15:54               ` Hannes Reinecke
2021-05-07  6:46                 ` Christoph Hellwig
2021-05-07 17:02                   ` Hannes Reinecke
2021-05-07 17:20                     ` Sagi Grimberg
2021-05-10  6:23                     ` Christoph Hellwig
2021-05-10 13:01                       ` Hannes Reinecke
2021-05-10 13:57                         ` Hannes Reinecke
2021-05-10 14:48                       ` Hannes Reinecke

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