Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756224Ab1DKWEI (ORCPT ); Mon, 11 Apr 2011 18:04:08 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:40144 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756115Ab1DKWEG (ORCPT ); Mon, 11 Apr 2011 18:04:06 -0400 Subject: [PATCH 2/3] make new alloc_pages_exact() To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Timur Tabi , Andi Kleen , Mel Gorman , Andrew Morton , Michal Nazarewicz , David Rientjes , Dave Hansen From: Dave Hansen Date: Mon, 11 Apr 2011 15:03:46 -0700 References: <20110411220345.9B95067C@kernel> In-Reply-To: <20110411220345.9B95067C@kernel> Message-Id: <20110411220346.2FED5787@kernel> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6650 Lines: 181 What I really wanted in the end was a highmem-capable alloc_pages_exact(), so here it is. This function can be used to allocate unmapped (like highmem) non-power-of-two-sized areas of memory. This is in constast to get_free_pages_exact() which can only allocate from lowmem. My plan is to use this in the virtio_balloon driver to allocate large, oddly-sized contiguous areas. The new __alloc_pages_exact() now takes a size in numbers of pages, and returns a 'struct page', which means it can now address highmem. It's a bit unfortunate that this introduces __free_pages_exact() alongside free_pages_exact(). But that mess already exists with __free_pages() vs. free_pages_exact(). So, at worst, this mirrors the mess that we already have. I'm also a bit worried that I've not put in something named alloc_pages_exact(), but that behaves differently than it did before this set. I got all of the in-tree cases, but I'm a bit worried about stragglers elsewhere. So, I'm calling this __alloc_pages_exact() for the moment. We can take out the __ some day if it bothers people. Note that the __get_free_pages() has a !GFP_HIGHMEM check. Now that we are using alloc_pages_exact() instead of __get_free_pages() for get_free_pages_exact(), we had to add a new check in get_free_pages_exact(). This has been compile and boot tested, and I checked that echo 2 > /sys/kernel/profiling still works, since it uses get_free_pages_exact(). Signed-off-by: Dave Hansen --- linux-2.6.git-dave/include/linux/gfp.h | 4 + linux-2.6.git-dave/mm/page_alloc.c | 84 ++++++++++++++++++++++++--------- 2 files changed, 67 insertions(+), 21 deletions(-) diff -puN include/linux/gfp.h~make_new_alloc_pages_exact include/linux/gfp.h --- linux-2.6.git/include/linux/gfp.h~make_new_alloc_pages_exact 2011-04-11 15:01:17.165822836 -0700 +++ linux-2.6.git-dave/include/linux/gfp.h 2011-04-11 15:01:17.177822831 -0700 @@ -351,6 +351,10 @@ extern struct page *alloc_pages_vma(gfp_ extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order); extern unsigned long get_zeroed_page(gfp_t gfp_mask); +/* 'struct page' version */ +struct page *__alloc_pages_exact(gfp_t gfp_mask, size_t size); +void __free_pages_exact(struct page *page, size_t size); +/* virtual address version */ void *get_free_pages_exact(gfp_t gfp_mask, size_t size); void free_pages_exact(void *virt, size_t size); diff -puN mm/page_alloc.c~make_new_alloc_pages_exact mm/page_alloc.c --- linux-2.6.git/mm/page_alloc.c~make_new_alloc_pages_exact 2011-04-11 15:01:17.169822835 -0700 +++ linux-2.6.git-dave/mm/page_alloc.c 2011-04-11 15:01:17.177822831 -0700 @@ -2318,9 +2318,10 @@ void free_pages(unsigned long addr, unsi EXPORT_SYMBOL(free_pages); /** - * get_free_pages_exact - allocate an exact number physically-contiguous pages. - * @size: the number of bytes to allocate + * __alloc_pages_exact - allocate an exact number physically-contiguous pages. + * @nr_pages: the number of pages to allocate * @gfp_mask: GFP flags for the allocation + * returns: struct page for allocated memory * * This function is similar to alloc_pages(), except that it allocates the * minimum number of pages to satisfy the request. alloc_pages() can only @@ -2330,29 +2331,75 @@ EXPORT_SYMBOL(free_pages); * * Memory allocated by this function must be released by free_pages_exact(). */ -void *get_free_pages_exact(gfp_t gfp_mask, size_t size) +struct page *__alloc_pages_exact(gfp_t gfp_mask, size_t nr_pages) { - unsigned int order = get_order(size); - unsigned long addr; + unsigned int order = get_order(nr_pages * PAGE_SIZE); + struct page *page; - addr = __get_free_pages(gfp_mask, order); - if (addr) { - unsigned long alloc_end = addr + (PAGE_SIZE << order); - unsigned long used = addr + PAGE_ALIGN(size); + page = alloc_pages(gfp_mask, order); + if (page) { + struct page *alloc_end = page + (1 << order); + struct page *used = page + nr_pages; - split_page(virt_to_page((void *)addr), order); + split_page(page, order); while (used < alloc_end) { - free_page(used); - used += PAGE_SIZE; + __free_page(used); + used++; } } - return (void *)addr; + return page; +} +EXPORT_SYMBOL(__alloc_pages_exact); + +/** + * __free_pages_exact - release memory allocated via __alloc_pages_exact() + * @virt: the value returned by get_free_pages_exact. + * @nr_pages: size in pages, same value as passed to __alloc_pages_exact(). + * + * Release the memory allocated by a previous call to __alloc_pages_exact(). + */ +void __free_pages_exact(struct page *page, size_t nr_pages) +{ + struct page *end = page + nr_pages; + + while (page < end) { + __free_page(page); + page++; + } +} +EXPORT_SYMBOL(__free_pages_exact); + +/** + * get_free_pages_exact - allocate an exact number physically-contiguous pages. + * @gfp_mask: GFP flags for the allocation + * @size: the number of bytes to allocate + * returns: virtual address of allocated memory + * + * This function is similar to __get_free_pages(), except that it allocates the + * minimum number of pages to satisfy the request. get_free_pages() can only + * allocate memory in power-of-two pages. + * + * This function is also limited by MAX_ORDER. + * + * Memory allocated by this function must be released by free_pages_exact(). + */ +void *get_free_pages_exact(gfp_t gfp_mask, size_t size) +{ + struct page *page; + + /* If we are using page_address(), we can not allow highmem */ + VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0); + + page = __alloc_pages_exact(gfp_mask, size * PAGE_SIZE); + if (page) + return (void *) page_address(page); + return NULL; } EXPORT_SYMBOL(get_free_pages_exact); /** - * free_pages_exact - release memory allocated via get_free_pages_exact() + * __free_pages_exact - release memory allocated via get_free_pages_exact() * @virt: the value returned by get_free_pages_exact. * @size: size of allocation, same value as passed to get_free_pages_exact(). * @@ -2360,13 +2407,8 @@ EXPORT_SYMBOL(get_free_pages_exact); */ void free_pages_exact(void *virt, size_t size) { - unsigned long addr = (unsigned long)virt; - unsigned long end = addr + PAGE_ALIGN(size); - - while (addr < end) { - free_page(addr); - addr += PAGE_SIZE; - } + int nr_pages = PAGE_ALIGN(size)/PAGE_SIZE; + __free_pages_exact(virt_to_page(virt), nr_pages); } EXPORT_SYMBOL(free_pages_exact); _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/