linux-kernel - Re: [PATCH v2 2/3] nvme/ioctl: don't call blk_mq_free_request() in nvme_map_user

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Message-ID: <20250327104232.GB10068@lst.de>
Date: Thu, 27 Mar 2025 11:42:32 +0100
From: Christoph Hellwig <hch@....de>
To: Caleb Sander Mateos <csander@...estorage.com>
Cc: Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] nvme/ioctl: don't call blk_mq_free_request() in
 nvme_map_user_request()

On Fri, Mar 21, 2025 at 02:57:21PM -0600, Caleb Sander Mateos wrote:
>  	ret = nvme_execute_rq(req, false);
>  	if (result)
>  		*result = le64_to_cpu(nvme_req(req)->result.u64);
>  	if (bio)
>  		blk_rq_unmap_user(bio);
> -	blk_mq_free_request(req);
>  
>  	if (effects)
>  		nvme_passthru_end(ctrl, ns, effects, cmd, ret);
>  
> +out_free_req:
> +	blk_mq_free_request(req);

We'll want the request freed before nvme_passthru_end here to avoid
deadlocks with namespaces scanning.