linux-kernel - Re: [PATCH] nvme-pci: add missing condition check for existence of mapped data

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Message-ID: <20240730172111.GA32320@lst.de>
Date: Tue, 30 Jul 2024 19:21:11 +0200
From: Christoph Hellwig <hch@....de>
To: Keith Busch <kbusch@...nel.org>
Cc: Leon Romanovsky <leon@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
	Leon Romanovsky <leonro@...dia.com>,
	Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme-pci: add missing condition check for existence of
 mapped data

On Tue, Jul 30, 2024 at 11:09:04AM -0600, Keith Busch wrote:
> > +	if (blk_rq_nr_phys_segments(req))
> > +		nvme_unmap_data(dev, req);
> 
> This is already applied, but it is kind of strange. We get here only if
> metadata mapping fails. Is there actually a command that has metadata
> without data?

Well, passthrough can always set metadata to map without data even
if there is no NVMe defined command that works that way, so we should
handle the error.

But I suspect this is due to Leon's dma-mapping work, and it probably
points to a bug in that :)