linux-kernel - Re: [PATCH v8 06/11] dma-buf: provide phys

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Message-ID: <20251119134526.GE18335@unreal>
Date: Wed, 19 Nov 2025 15:45:26 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: "Tian, Kevin" <kevin.tian@...el.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>, Jens Axboe <axboe@...nel.dk>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	Kees Cook <kees@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Ankit Agrawal <ankita@...dia.com>,
	Yishai Hadas <yishaih@...dia.com>,
	Shameer Kolothum <skolothumtho@...dia.com>,
	Alex Williamson <alex@...zbot.org>,
	Krishnakant Jaju <kjaju@...dia.com>, Matt Ochs <mochs@...dia.com>,
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	Alex Mastro <amastro@...com>, Nicolin Chen <nicolinc@...dia.com>
Subject: Re: [PATCH v8 06/11] dma-buf: provide phys_vec to scatter-gather
 mapping routine

On Wed, Nov 19, 2025 at 09:37:08AM -0400, Jason Gunthorpe wrote:
> On Wed, Nov 19, 2025 at 03:30:00PM +0200, Leon Romanovsky wrote:
> > On Wed, Nov 19, 2025 at 05:54:55AM +0000, Tian, Kevin wrote:
> > > > From: Leon Romanovsky <leon@...nel.org>
> > > > Sent: Tuesday, November 11, 2025 5:58 PM
> > > > +
> > > > +	if (dma->state && dma_use_iova(dma->state)) {
> > > > +		WARN_ON_ONCE(mapped_len != size);
> > > 
> > > then "goto err_unmap_dma".
> > 
> > It never should happen, there is no need to provide error unwind to
> > something that you won't get.
> 
> It is expected that WARN_ON has recovery code, if it is possible and
> not burdensome.

It’s not necessary, but since I’m calculating mapped_len again, it’s natural—and completely
harmless—to double-check the arithmetic.

Thanks

> 
> Jason