From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ADA1916400 for ; Fri, 9 Jun 2023 13:44:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7DE1FC433D2; Fri, 9 Jun 2023 13:44:04 +0000 (UTC) Date: Fri, 9 Jun 2023 14:44:01 +0100 From: Catalin Marinas To: Vlastimil Babka Cc: Linus Torvalds , Christoph Hellwig , Robin Murphy , Arnd Bergmann , Greg Kroah-Hartman , Will Deacon , Marc Zyngier , Andrew Morton , Herbert Xu , Ard Biesheuvel , Isaac Manjarres , Saravana Kannan , Alasdair Kergon , Daniel Vetter , Joerg Roedel , Mark Brown , Mike Snitzer , "Rafael J. Wysocki" , Jonathan Cameron , linux-mm@kvack.org, iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v6 01/17] mm/slab: Decouple ARCH_KMALLOC_MINALIGN from ARCH_DMA_MINALIGN Message-ID: References: <20230531154836.1366225-1-catalin.marinas@arm.com> <20230531154836.1366225-2-catalin.marinas@arm.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jun 09, 2023 at 02:32:57PM +0200, Vlastimil Babka wrote: > On 5/31/23 17:48, Catalin Marinas wrote: > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > > index 0ee20b764000..3288a1339271 100644 > > --- a/include/linux/dma-mapping.h > > +++ b/include/linux/dma-mapping.h > > @@ -545,7 +545,7 @@ static inline int dma_set_min_align_mask(struct device *dev, > > > > static inline int dma_get_cache_alignment(void) > > { > > -#ifdef ARCH_DMA_MINALIGN > > +#ifdef ARCH_HAS_DMA_MINALIGN > > return ARCH_DMA_MINALIGN; > > #endif > > return 1; > > diff --git a/include/linux/slab.h b/include/linux/slab.h > > index 6b3e155b70bf..50dcf9cfbf62 100644 > > --- a/include/linux/slab.h > > +++ b/include/linux/slab.h > > @@ -235,12 +235,20 @@ void kmem_dump_obj(void *object); > > * alignment larger than the alignment of a 64-bit integer. > > * Setting ARCH_DMA_MINALIGN in arch headers allows that. > > */ > > -#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8 > > +#ifdef ARCH_DMA_MINALIGN > > +#define ARCH_HAS_DMA_MINALIGN > > +#if ARCH_DMA_MINALIGN > 8 && !defined(ARCH_KMALLOC_MINALIGN) > > #define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN > > -#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN > > -#define KMALLOC_SHIFT_LOW ilog2(ARCH_DMA_MINALIGN) > > +#endif > > #else > > +#define ARCH_DMA_MINALIGN __alignof__(unsigned long long) > > +#endif > > It seems weird to make slab.h responsible for this part, especially for > #define ARCH_HAS_DMA_MINALIGN, which dma-mapping.h consumes. Maybe it would > be difficult to do differently due to some dependency hell, but minimally I > don't see dma-mapping.h including slab.h so the result is > include-order-dependent? Maybe it's included transitively, but then it's > fragile and would be better to do explicitly? True, there's a risk that it doesn't get included with some future header refactoring. What about moving ARCH_DMA_MINALIGN to linux/cache.h? Alternatively, I could create a new linux/dma-minalign.h file but I feel since this is about caches, having it in cache.h makes more sense. asm/cache.h is also where most archs define the constant (apart from mips, sh, microblaze). -- Catalin