From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 17 Mar 2008 09:56:04 +0100 From: Andi Kleen Subject: Re: [PATCH] [11/18] Fix alignment bug in bootmem allocator Message-ID: <20080317085604.GA12405@basil.nowhere.org> References: <20080317258.659191058@firstfloor.org> <20080317015825.0C0171B41E0@basil.firstfloor.org> <86802c440803161919h20ed9f78k6e3798ef56668638@mail.gmail.com> <20080317070208.GC27015@one.firstfloor.org> <86802c440803170017r622114bdpede8625d1a8ff585@mail.gmail.com> <86802c440803170031u75167e5m301f65049b6d62ff@mail.gmail.com> <20080317074146.GG27015@one.firstfloor.org> <86802c440803170053n32a1c918h2ff2a32abef44050@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86802c440803170053n32a1c918h2ff2a32abef44050@mail.gmail.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Yinghai Lu Cc: Andi Kleen , linux-kernel@vger.kernel.org, pj@sgi.com, linux-mm@kvack.org, nickpiggin@yahoo.com.au List-ID: > only happen when align is large than alignment of node_boot_start. Here's an updated version of the patch with this addressed. Please review. The patch is somewhat more complicated, but actually makes the code a little cleaner now. -Andi Fix alignment bug in bootmem allocator Without this fix bootmem can return unaligned addresses when the start of a node is not aligned to the align value. Needed for reliably allocating gigabyte pages. I removed the offset variable because all tests should align themself correctly now. Slight drawback might be that the bootmem allocator will spend some more time skipping bits in the bitmap initially, but that shouldn't be a big issue. Signed-off-by: Andi Kleen --- mm/bootmem.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) Index: linux/mm/bootmem.c =================================================================== --- linux.orig/mm/bootmem.c +++ linux/mm/bootmem.c @@ -195,8 +195,9 @@ void * __init __alloc_bootmem_core(struct bootmem_data *bdata, unsigned long size, unsigned long align, unsigned long goal, unsigned long limit) { - unsigned long offset, remaining_size, areasize, preferred; - unsigned long i, start = 0, incr, eidx, end_pfn; + unsigned long remaining_size, areasize, preferred; + unsigned long i, start, incr, eidx, end_pfn; + unsigned long pfn; void *ret; if (!size) { @@ -218,10 +219,6 @@ __alloc_bootmem_core(struct bootmem_data end_pfn = limit; eidx = end_pfn - PFN_DOWN(bdata->node_boot_start); - offset = 0; - if (align && (bdata->node_boot_start & (align - 1UL)) != 0) - offset = align - (bdata->node_boot_start & (align - 1UL)); - offset = PFN_DOWN(offset); /* * We try to allocate bootmem pages above 'goal' @@ -236,15 +233,18 @@ __alloc_bootmem_core(struct bootmem_data } else preferred = 0; - preferred = PFN_DOWN(ALIGN(preferred, align)) + offset; + start = bdata->node_boot_start; + preferred = PFN_DOWN(ALIGN(preferred + start, align) - start); areasize = (size + PAGE_SIZE-1) / PAGE_SIZE; incr = align >> PAGE_SHIFT ? : 1; + pfn = PFN_DOWN(start); + start = 0; restart_scan: for (i = preferred; i < eidx; i += incr) { unsigned long j; i = find_next_zero_bit(bdata->node_bootmem_map, eidx, i); - i = ALIGN(i, incr); + i = ALIGN(pfn + i, incr) - pfn; if (i >= eidx) break; if (test_bit(i, bdata->node_bootmem_map)) @@ -258,11 +258,11 @@ restart_scan: start = i; goto found; fail_block: - i = ALIGN(j, incr); + i = ALIGN(j + pfn, incr) - pfn; } - if (preferred > offset) { - preferred = offset; + if (preferred > 0) { + preferred = 0; goto restart_scan; } return NULL; @@ -278,7 +278,7 @@ found: */ if (align < PAGE_SIZE && bdata->last_offset && bdata->last_pos+1 == start) { - offset = ALIGN(bdata->last_offset, align); + unsigned long offset = ALIGN(bdata->last_offset, align); BUG_ON(offset > PAGE_SIZE); remaining_size = PAGE_SIZE - offset; if (size < remaining_size) { -- 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