linux-kernel - Re: [PATCH v5 04/12] nvmet-fc: defer cleanup using RCU properly

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Date: Thu, 1 Feb 2024 13:43:38 +0100
From: Hannes Reinecke <hare@...e.de>
To: Daniel Wagner <dwagner@...e.de>, James Smart <james.smart@...adcom.com>
Cc: Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>,
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 04/12] nvmet-fc: defer cleanup using RCU properly

On 1/31/24 09:51, Daniel Wagner wrote:
> When the target executes a disconnect and the host triggers a reconnect
> immediately, the reconnect command still finds an existing association.
> 
> The reconnect crashes later on because nvmet_fc_delete_target_assoc
> blindly removes resources while the reconnect code wants to use it.
> 
> To address this, nvmet_fc_find_target_assoc should not be able to
> lookup an association which is being removed. The association list
> is already under RCU lifetime management, so let's properly use it
> and remove the association from the list and wait for a grace period
> before cleaning up all. This means we also can drop the RCU management
> on the queues, because this is now handled via the association itself.
> 
> A second step split the execution context so that the initial disconnect
> command can complete without running the reconnect code in the same
> context. As usual, this is done by deferring the ->done to a workqueue.
> 
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Daniel Wagner <dwagner@...e.de>
> ---
>   drivers/nvme/target/fc.c | 83 ++++++++++++++++++----------------------
>   1 file changed, 37 insertions(+), 46 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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