The patch titled
Subject: bootmem/sparsemem: remove limit constraint in alloc_bootmem_section
has been added to the -mm tree. Its filename is
bootmem-sparsemem-remove-limit-constraint-in-alloc_bootmem_section.patch
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From: Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx>
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.
Signed-off-by: Nishanth Aravamudan <nacc@xxxxxxxxxx>
Cc: Dave Hansen <haveblue@xxxxxxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Ben Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Robert Jennings <rcj@xxxxxxxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.3.1]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/bootmem.c | 2 +-
mm/sparse.c | 30 +++++++++++-------------------
2 files changed, 12 insertions(+), 20 deletions(-)
diff -puN mm/bootmem.c~bootmem-sparsemem-remove-limit-constraint-in-alloc_bootmem_section mm/bootmem.c
--- a/mm/bootmem.c~bootmem-sparsemem-remove-limit-constraint-in-alloc_bootmem_section
+++ a/mm/bootmem.c
@@ -770,7 +770,7 @@ void * __init alloc_bootmem_section(unsi
pfn = section_nr_to_pfn(section_nr);
goal = pfn << PAGE_SHIFT;
- limit = section_nr_to_pfn(section_nr + 1) << PAGE_SHIFT;
+ limit = 0;
bdata = &bootmem_node_data[early_pfn_to_nid(pfn)];
return alloc_bootmem_core(bdata, size, SMP_CACHE_BYTES, goal, limit);
diff -puN mm/sparse.c~bootmem-sparsemem-remove-limit-constraint-in-alloc_bootmem_section mm/sparse.c
--- a/mm/sparse.c~bootmem-sparsemem-remove-limit-constraint-in-alloc_bootmem_section
+++ a/mm/sparse.c
@@ -353,29 +353,21 @@ static void __init sparse_early_usemaps_
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
_
Subject: Subject: bootmem/sparsemem: remove limit constraint in alloc_bootmem_section
Patches currently in -mm which might be from nacc@xxxxxxxxxxxxxxxxxx are
bootmem-sparsemem-remove-limit-constraint-in-alloc_bootmem_section.patch
bootmem-sparsemem-remove-limit-constraint-in-alloc_bootmem_section-fix.patch
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