Re: [PATCH] sparsemem/bootmem: catch greater than section size allocations
From: Johannes Weiner <hannes@cmpxchg.org>
Date: 2012-02-28 13:54:06
Also in:
linux-mm
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
On Fri, Feb 24, 2012 at 11:33:58AM -0800, Nishanth Aravamudan wrote:
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 -> alloc_bootmem_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
disable the limit check if the size of the allocation in
alloc_bootmem_secition exceeds the section size.It makes sense to allow the usemaps to spill over to subsequent sections instead of panicking, so FWIW: Acked-by: Johannes Weiner <hannes@cmpxchg.org> That being said, it would be good if check_usemap_section_nr() printed the cross-dependencies between pgdats and sections when the usemaps of a node spilled over to other sections than the ones holding the pgdat. How about this? --- From: Johannes Weiner <hannes@cmpxchg.org> Subject: sparsemem/bootmem: catch greater than section size allocations fix 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. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> ---
diff --git a/mm/sparse.c b/mm/sparse.c
index 61d7cde..9e032dc 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c@@ -359,6 +359,7 @@ static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map, continue; usemap_map[pnum] = usemap; usemap += size; + check_usemap_section_nr(nodeid, usemap_map[pnum]); } return; } ---
Furthermore, I wonder if we can remove the sparse-specific stuff from bootmem.c as well, as now even more so than before, calculating the desired area is really none of bootmem's business. Would something like this be okay? --- From: Johannes Weiner <hannes@cmpxchg.org> Subject: [patch] mm: remove sparsemem allocation details from the bootmem allocator alloc_bootmem_section() derives allocation area constraints from the specified sparsemem section. This is a bit specific for a generic memory allocator like bootmem, though, so move it over to sparsemem. Since __alloc_bootmem_node() already retries failed allocations with relaxed area constraints, the fallback code in sparsemem.c can be removed and the code becomes a bit more compact overall. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> --- include/linux/bootmem.h | 3 --- mm/bootmem.c | 26 -------------------------- mm/sparse.c | 29 +++++++++-------------------- 3 files changed, 9 insertions(+), 49 deletions(-)
diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index ab344a5..001c248 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h@@ -135,9 +135,6 @@ extern void *__alloc_bootmem_low_node(pg_data_t *pgdat, extern int reserve_bootmem_generic(unsigned long addr, unsigned long size, int flags); -extern void *alloc_bootmem_section(unsigned long size, - unsigned long section_nr); - #ifdef CONFIG_HAVE_ARCH_ALLOC_REMAP extern void *alloc_remap(int nid, unsigned long size); #else
diff --git a/mm/bootmem.c b/mm/bootmem.c
index 7bc0557..d34026c 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c@@ -756,32 +756,6 @@ void * __init __alloc_bootmem_node_high(pg_data_t *pgdat, unsigned long size, } -#ifdef CONFIG_SPARSEMEM -/** - * alloc_bootmem_section - allocate boot memory from a specific section - * @size: size of the request in bytes - * @section_nr: sparse map section to allocate from - * - * Return NULL on failure. - */ -void * __init alloc_bootmem_section(unsigned long size, - unsigned long section_nr) -{ - bootmem_data_t *bdata; - unsigned long pfn, goal, limit; - - pfn = section_nr_to_pfn(section_nr); - goal = pfn << PAGE_SHIFT; - if (size > BYTES_PER_SECTION) - limit = 0; - else - limit = section_nr_to_pfn(section_nr + 1) << PAGE_SHIFT; - bdata = &bootmem_node_data[early_pfn_to_nid(pfn)]; - - return alloc_bootmem_core(bdata, size, SMP_CACHE_BYTES, goal, limit); -} -#endif - void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size, unsigned long align, unsigned long goal) {
diff --git a/mm/sparse.c b/mm/sparse.c
index 9e032dc..ac0d5a3 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c@@ -273,10 +273,10 @@ static unsigned long *__kmalloc_section_usemap(void) #ifdef CONFIG_MEMORY_HOTREMOVE static unsigned long * __init sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, - unsigned long count) + unsigned long size) { - unsigned long section_nr; - + pg_data_t *host_pgdat; + unsigned long goal; /* * A page may contain usemaps for other sections preventing the * page being freed and making a section unremovable while
@@ -287,8 +287,9 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, * from the same section as the pgdat where possible to avoid * this problem. */ - section_nr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT); - return alloc_bootmem_section(usemap_size() * count, section_nr); + goal = __pa(pgdat) & PAGE_SECTION_MASK; + host_pgdat = NODE_DATA(early_pfn_to_nid(goal)); + return __alloc_bootmem_node(host_pgdat, size, SMP_CACHE_BYTES, goal); } static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
@@ -332,9 +333,9 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap) #else static unsigned long * __init sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, - unsigned long count) + unsigned long size) { - return NULL; + return alloc_bootmem_node(pgdat, size); } static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
@@ -352,19 +353,7 @@ static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map, int size = usemap_size(); 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; - check_usemap_section_nr(nodeid, usemap_map[pnum]); - } - return; - } - - usemap = alloc_bootmem_node(NODE_DATA(nodeid), size * usemap_count); + size * usemap_count); if (usemap) { for (pnum = pnum_begin; pnum < pnum_end; pnum++) { if (!present_section_nr(pnum))
--
1.7.7.6