From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx147.postini.com [74.125.245.147]) by kanga.kvack.org (Postfix) with SMTP id 7C4EB6B0044 for ; Fri, 24 Aug 2012 08:22:32 -0400 (EDT) Received: from epcpsbgm2.samsung.com (mailout2.samsung.com [203.254.224.25]) by mailout2.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0M99007IBECA4WV0@mailout2.samsung.com> for linux-mm@kvack.org; Fri, 24 Aug 2012 21:21:46 +0900 (KST) Received: from AMDC159 ([106.116.147.30]) by mmp1.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTPA id <0M9900BCXEBM6G90@mmp1.samsung.com> for linux-mm@kvack.org; Fri, 24 Aug 2012 21:21:46 +0900 (KST) From: Marek Szyprowski References: <1345796945-21115-1-git-send-email-hdoyu@nvidia.com> <1345796945-21115-2-git-send-email-hdoyu@nvidia.com> <20120824111323.GB11007@konrad-lan.dumpdata.com> <20120824.145200.843951079622652894.hdoyu@nvidia.com> In-reply-to: <20120824.145200.843951079622652894.hdoyu@nvidia.com> Subject: RE: [v3 1/4] ARM: dma-mapping: atomic_pool with struct page **pages Date: Fri, 24 Aug 2012 14:21:22 +0200 Message-id: <026901cd81f2$fffea680$fffbf380$%szyprowski@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7bit Content-language: pl Sender: owner-linux-mm@kvack.org List-ID: To: 'Hiroshi Doyu' , konrad.wilk@oracle.com Cc: linux-arm-kernel@lists.infradead.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kyungmin.park@samsung.com, arnd@arndb.de, linux@arm.linux.org.uk, chunsang.jeong@linaro.org, 'Krishna Reddy' , subashrp@gmail.com, minchan@kernel.org, pullip.cho@samsung.com Hello, On Friday, August 24, 2012 1:52 PM Hiroshi Doyu wrote: > Konrad Rzeszutek Wilk wrote @ Fri, 24 Aug 2012 13:13:23 +0200: > > > On Fri, Aug 24, 2012 at 11:29:02AM +0300, Hiroshi Doyu wrote: > > > struct page **pages is necessary to align with non atomic path in > > > __iommu_get_pages(). atomic_pool() has the intialized **pages instead > > > of just *page. > > > > > > Signed-off-by: Hiroshi Doyu > > > --- > > > arch/arm/mm/dma-mapping.c | 17 +++++++++++++---- > > > 1 files changed, 13 insertions(+), 4 deletions(-) > > > > > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > > > index 601da7a..b14ee64 100644 > > > --- a/arch/arm/mm/dma-mapping.c > > > +++ b/arch/arm/mm/dma-mapping.c > > > @@ -296,7 +296,7 @@ struct dma_pool { > > > unsigned long *bitmap; > > > unsigned long nr_pages; > > > void *vaddr; > > > - struct page *page; > > > + struct page **pages; > > > }; > > > > > > static struct dma_pool atomic_pool = { > > > @@ -335,12 +335,16 @@ static int __init atomic_pool_init(void) > > > unsigned long nr_pages = pool->size >> PAGE_SHIFT; > > > unsigned long *bitmap; > > > struct page *page; > > > + struct page **pages; > > > void *ptr; > > > int bitmap_size = BITS_TO_LONGS(nr_pages) * sizeof(long); > > > + size_t size = nr_pages * sizeof(struct page *); > > > > > > - bitmap = kzalloc(bitmap_size, GFP_KERNEL); > > > + size += bitmap_size; > > > + bitmap = kzalloc(size, GFP_KERNEL); > > > if (!bitmap) > > > goto no_bitmap; > > > + pages = (void *)bitmap + bitmap_size; > > > > So you stuck a bitmap field in front of the array then? > > Why not just define a structure where this is clearly defined > > instead of doing the casting. > > I just wanted to allocate only once for the members "pool->bitmap" and > "pool->pages" at once. Since the size of a whole bitmap isn't known in > advance, I couldn't find any fixed type for this bitmap, which pointer > can be shifted without casting. IOW, they are variable length. IMHO it is better to avoid any non-trivial things in generic arch code. Merging those 2 allocations doesn't save any significant bit of memory and might confuse someone. Better just allocate them separately. Best regards -- Marek Szyprowski Samsung Poland R&D Center -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org