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Tue, 21 Jul 2026 11:55:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E50E81F000E9; Tue, 21 Jul 2026 11:54:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784634901; bh=UJXno+NE2LaIdHpYv/4s8ue4/cjDLWXaEa8lFS8q5GY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=F95kPevlSn1NQmmXdgfNRRHtm8wP1sXWeSsajbmTVkqIVzEt4omP7+o8h/zzqgon8 aO2X352TPWBumHybCH5wICorK7tHQOJ+DLfga1PMxYtgGyqAr1d75R36jZQcoAZQ0G u4Ltzvzc8UN19pVa60sSITfwm9xlmo7Hr5kTf7or5X1dbKVS99JrE6bfnBoFbv+ckQ REkQsHFwee8HrNaRT8lHJe7QWLL3u2KfR4piTx/+d8f8FoJDJV6XZZXLGbwgVG6/2w R3oYpiCOUEawrQ7xZmqfEe7FPeRTR/3x9h6o8gh9596QPZeiwtdrlz0QLXVFYHGROp Opr9JesAwQ3ow== Date: Tue, 21 Jul 2026 14:54:56 +0300 From: Leon Romanovsky To: "Aneesh Kumar K.V (Arm)" Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org, stable@vger.kernel.org, Michael Kelley , Jason Gunthorpe Subject: Re: [PATCH v8 01/23] dma-direct: return struct page from dma_direct_alloc_from_pool() Message-ID: <20260721115456.GI110966@unreal> References: <20260717180442.110954-1-aneesh.kumar@kernel.org> <20260717180442.110954-2-aneesh.kumar@kernel.org> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260717180442.110954-2-aneesh.kumar@kernel.org> On Fri, Jul 17, 2026 at 11:34:19PM +0530, Aneesh Kumar K.V (Arm) wrote: > Commit 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool > helper") changed dma_direct_alloc_from_pool() to return the CPU address > from dma_alloc_from_pool(). That fits dma_direct_alloc(), but > dma_direct_alloc_pages() also uses the helper and expects a struct page *. > > Fix this by making dma_direct_alloc_from_pool() return the struct page * > again, and pass the CPU address back through an out-parameter for the > dma_direct_alloc() caller. > > Fixes: 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool helper") > Cc: stable@vger.kernel.org > Tested-by: Michael Kelley > Tested-by: Mostafa Saleh > Reviewed-by: Jason Gunthorpe > Signed-off-by: Aneesh Kumar K.V (Arm) > --- > kernel/dma/direct.c | 18 ++++++++++-------- > 1 file changed, 10 insertions(+), 8 deletions(-) > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index d8219efe3273..363d984d90e7 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -164,22 +164,21 @@ static bool dma_direct_use_pool(struct device *dev, gfp_t gfp) > return !gfpflags_allow_blocking(gfp) && !is_swiotlb_for_alloc(dev); > } > > -static void *dma_direct_alloc_from_pool(struct device *dev, size_t size, > - dma_addr_t *dma_handle, gfp_t gfp) > +static struct page *dma_direct_alloc_from_pool(struct device *dev, size_t size, > + dma_addr_t *dma_handle, void **cpu_addr, gfp_t gfp) > { > struct page *page; > u64 phys_limit; > - void *ret; > > if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_DMA_COHERENT_POOL))) > return NULL; > > gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit); > - page = dma_alloc_from_pool(dev, size, &ret, gfp, dma_coherent_ok); > + page = dma_alloc_from_pool(dev, size, cpu_addr, gfp, dma_coherent_ok); > if (!page) > return NULL; > *dma_handle = phys_to_dma_direct(dev, page_to_phys(page)); > - return ret; > + return page; > } > > static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size, > @@ -247,8 +246,11 @@ void *dma_direct_alloc(struct device *dev, size_t size, > * the atomic pools instead if we aren't allowed block. > */ > if ((remap || force_dma_unencrypted(dev)) && > - dma_direct_use_pool(dev, gfp)) > - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > + dma_direct_use_pool(dev, gfp)) { > + page = dma_direct_alloc_from_pool(dev, size, dma_handle, > + &ret, gfp); > + return page ? ret : NULL; Sorry for joining the discussion late, but the line above caught my attention. Why do we need both ret and page? We can derive cpu_addr from page and vice versa. Do we really need the &ret parameter? Or, more generally, do we really need "struct page *"? static struct page *__dma_alloc_from_pool(struct device *dev, size_t size, struct gen_pool *pool, void **cpu_addr, bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t)) { ... *cpu_addr = (void *)addr; memset(*cpu_addr, 0, size); return pfn_to_page(__phys_to_pfn(phys)); } Why > + } > > /* we always manually zero the memory once we are done */ > page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true); > @@ -357,7 +359,7 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size, > void *ret; > > if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp)) > - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > + return dma_direct_alloc_from_pool(dev, size, dma_handle, &ret, gfp); > > page = __dma_direct_alloc_pages(dev, size, gfp, false); > if (!page) > -- > 2.43.0 > >