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Date: Tue, 9 Jun 2026 09:41:22 +0200
From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>, Jonathan Corbet <corbet@lwn.net>,
	Damien Le Moal <dlemoal@kernel.org>, Hannes Reinecke <hare@suse.de>,
	Keith Busch <kbusch@kernel.org>, linux-block@vger.kernel.org,
	linux-doc@vger.kernel.org, Hannes Reinecke <hare@kernel.org>
Subject: Re: [PATCH 4/4] block: add configurable error injection
Message-ID: <20260609074122.GB6877@lst.de>
References: <20260608051416.1205282-1-hch@lst.de> <20260608051416.1205282-5-hch@lst.de> <bac50400-dd86-4c7f-bab3-481c1306877b@kernel.dk>
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On Mon, Jun 08, 2026 at 08:53:22AM -0600, Jens Axboe wrote:
> > +	if (!test_bit(GD_ERROR_INJECT, &bio->bi_bdev->bd_disk->state))
> > +		return false;
> > +	return __blk_error_inject(bio);
> > +}
> 
> I really hate this part, that's a pretty deep set of pointer chasings to
> figure out if injection is enabled or not,

It's to the bdev we use everywhere, and then to the disk which we use
in a lot of places in the submission path.

The only easy way to reduce it would be to move the state to the
block_device.  We currently don't do partitions in debugfs, but maybe
we should?

> when in practice error
> injection is only ever enabled for specific test cases and distros
> invariably will set CONFIG_BLK_ERROR_INJECTION because they turn on
> every damn thing under the sun.
> 
> IOW, that won't fly for the hot path. Maybe a static key would be useful
> here?

a static_key makes sense here, probably including the legacy error
injection.