linux-kernel - Re: [PATCH v3 4/8] blk-mp: introduce blk_mq_hctx_map

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Message-ID: <c8c671c1-267a-4aa7-a64b-51a461176ad3@flourine.local>
Date: Tue, 12 Nov 2024 16:33:09 +0100
From: Daniel Wagner <dwagner@...e.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Daniel Wagner <wagi@...nel.org>, Jens Axboe <axboe@...nel.dk>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, "Michael S. Tsirkin" <mst@...hat.com>, 
	Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Eugenio Pérez <eperezma@...hat.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	Keith Busch <kbusch@...nel.org>, Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, 
	virtualization@...ts.linux.dev, linux-scsi@...r.kernel.org, megaraidlinux.pdl@...adcom.com, 
	mpi3mr-linuxdrv.pdl@...adcom.com, MPT-FusionLinux.pdl@...adcom.com, storagedev@...rochip.com, 
	linux-nvme@...ts.infradead.org
Subject: Re: [PATCH v3 4/8] blk-mp: introduce blk_mq_hctx_map_queues

On Tue, Nov 12, 2024 at 02:58:43PM +0100, Greg Kroah-Hartman wrote:
> > +void blk_mq_hctx_map_queues(struct blk_mq_queue_map *qmap,
> > +			    struct device *dev, unsigned int offset)
> > +
> > +{
> > +	const struct cpumask *mask;
> > +	unsigned int queue, cpu;
> > +
> > +	if (!dev->bus->irq_get_affinity)
> > +		goto fallback;
> 
> I think this is better than hard-coding it, but are you sure that the
> bus will always be bound to the device here so that you have a valid
> bus-> pointer?

No, I just assumed the bus pointer is always valid. If it is possible to
have a device without a bus, than I'll better extend the condition to

	if (!dev->bus || !dev->bus->irq_get_affinity)
        	goto fallback;