From f5bf18fa22f8c41a13eb8762c7373eb3a93a7333 Mon Sep 17 00:00:00 2001 From: Nishanth Aravamudan Date: Wed, 21 Mar 2012 16:34:07 -0700 Subject: bootmem/sparsemem: remove limit constraint in alloc_bootmem_section While testing AMS (Active Memory Sharing) / CMO (Cooperative Memory Overcommit) on powerpc, we tripped the following: kernel BUG at mm/bootmem.c:483! cpu 0x0: Vector: 700 (Program Check) at [c000000000c03940] pc: c000000000a62bd8: .alloc_bootmem_core+0x90/0x39c lr: c000000000a64bcc: .sparse_early_usemaps_alloc_node+0x84/0x29c sp: c000000000c03bc0 msr: 8000000000021032 current = 0xc000000000b0cce0 paca = 0xc000000001d80000 pid = 0, comm = swapper kernel BUG at mm/bootmem.c:483! enter ? for help [c000000000c03c80] c000000000a64bcc .sparse_early_usemaps_alloc_node+0x84/0x29c [c000000000c03d50] c000000000a64f10 .sparse_init+0x12c/0x28c [c000000000c03e20] c000000000a474f4 .setup_arch+0x20c/0x294 [c000000000c03ee0] c000000000a4079c .start_kernel+0xb4/0x460 [c000000000c03f90] c000000000009670 .start_here_common+0x1c/0x2c This is BUG_ON(limit && goal + size > limit); and after some debugging, it seems that goal = 0x7ffff000000 limit = 0x80000000000 and sparse_early_usemaps_alloc_node -> sparse_early_usemaps_alloc_pgdat_section calls return alloc_bootmem_section(usemap_size() * count, section_nr); This is on a system with 8TB available via the AMS pool, and as a quirk of AMS in firmware, all of that memory shows up in node 0. So, we end up with an allocation that will fail the goal/limit constraints. In theory, we could "fall-back" to alloc_bootmem_node() in sparse_early_usemaps_alloc_node(), but since we actually have HOTREMOVE defined, we'll BUG_ON() instead. A simple solution appears to be to unconditionally remove the limit condition in alloc_bootmem_section, meaning allocations are allowed to cross section boundaries (necessary for systems of this size). Johannes Weiner pointed out that if alloc_bootmem_section() no longer guarantees section-locality, we need check_usemap_section_nr() to print possible cross-dependencies between node descriptors and the usemaps allocated through it. That makes the two loops in sparse_early_usemaps_alloc_node() identical, so re-factor the code a bit. [akpm@linux-foundation.org: code simplification] Signed-off-by: Nishanth Aravamudan Cc: Dave Hansen Cc: Anton Blanchard Cc: Paul Mackerras Cc: Ben Herrenschmidt Cc: Robert Jennings Acked-by: Johannes Weiner Acked-by: Mel Gorman Cc: [3.3.1] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/sparse.c | 30 +++++++++++------------------- 1 file changed, 11 insertions(+), 19 deletions(-) (limited to 'mm/sparse.c') diff --git a/mm/sparse.c b/mm/sparse.c index 61d7cde23111..a8bc7d364deb 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -353,29 +353,21 @@ static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map, usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nodeid), usemap_count); - if (usemap) { - for (pnum = pnum_begin; pnum < pnum_end; pnum++) { - if (!present_section_nr(pnum)) - continue; - usemap_map[pnum] = usemap; - usemap += size; + if (!usemap) { + usemap = alloc_bootmem_node(NODE_DATA(nodeid), size * usemap_count); + if (!usemap) { + printk(KERN_WARNING "%s: allocation failed\n", __func__); + return; } - return; } - usemap = alloc_bootmem_node(NODE_DATA(nodeid), size * usemap_count); - if (usemap) { - for (pnum = pnum_begin; pnum < pnum_end; pnum++) { - if (!present_section_nr(pnum)) - continue; - usemap_map[pnum] = usemap; - usemap += size; - check_usemap_section_nr(nodeid, usemap_map[pnum]); - } - return; + for (pnum = pnum_begin; pnum < pnum_end; pnum++) { + if (!present_section_nr(pnum)) + continue; + usemap_map[pnum] = usemap; + usemap += size; + check_usemap_section_nr(nodeid, usemap_map[pnum]); } - - printk(KERN_WARNING "%s: allocation failed\n", __func__); } #ifndef CONFIG_SPARSEMEM_VMEMMAP -- cgit v1.2.3