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Date: Thu, 29 Aug 2024 06:28:14 +0200
From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Puranjay Mohan <pjy@amazon.com>, Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
	puranjay@kernel.org
Subject: Re: [PATCH v2] nvme: check if the namespace supports metadata in
 nvme_map_user_request()
Message-ID: <20240829042814.GA4644@lst.de>
References: <20240827132327.1704-1-pjy@amazon.com> <Zs8360kRPGa1B5xy@kbusch-mbp>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Wed, Aug 28, 2024 at 08:44:59AM -0600, Keith Busch wrote:
> On Tue, Aug 27, 2024 at 01:23:27PM +0000, Puranjay Mohan wrote:
> > @@ -119,9 +120,13 @@ static int nvme_map_user_request(struct request *req, u64 ubuffer,
> >  	struct request_queue *q = req->q;
> >  	struct nvme_ns *ns = q->queuedata;
> >  	struct block_device *bdev = ns ? ns->disk->part0 : NULL;
> > +	bool has_metadata = bdev && meta_buffer && meta_len;
> 
> If this is an admin command, then bdev is NULL, so "has_metadata" is
> false.
> 
> Since has_metadata is false, we continue on to process this admin
> command, but ignore the user's metadata settings. Do we want to return
> error there too?

Ah yes.  I had my brain wrapped around this the wrong way the
entire time.

Maybe a 

	bool supports_metadata = bdev && blk_get_integrity(bdev->bd_disk);
	bool has_metadata = meta_buffer && meta_len;

might help poor brains like mine.