From: Qian Cai <cai@xxxxxx>
[ Upstream commit 1a9f219157b22d0ffb340a9c5f431afd02cd2cf3 ]
has_unmovable_pages() is used by allocating CMA and gigantic pages as
well as the memory hotplug. The later doesn't know how to offline CMA
pool properly now, but if an unused (free) CMA page is encountered, then
has_unmovable_pages() happily considers it as a free memory and
propagates this up the call chain. Memory offlining code then frees the
page without a proper CMA tear down which leads to an accounting issues.
Moreover if the same memory range is onlined again then the memory never
gets back to the CMA pool.
State after memory offline:
# grep cma /proc/vmstat
nr_free_cma 205824
# cat /sys/kernel/debug/cma/cma-kvm_cma/count
209920
Also, kmemleak still think those memory address are reserved below but
have already been used by the buddy allocator after onlining. This
patch fixes the situation by treating CMA pageblocks as unmovable except
when has_unmovable_pages() is called as part of CMA allocation.
Offlined Pages 4096
kmemleak: Cannot insert 0xc000201f7d040008 into the object search tree (overlaps existing)
Call Trace:
dump_stack+0xb0/0xf4 (unreliable)
create_object+0x344/0x380
__kmalloc_node+0x3ec/0x860
kvmalloc_node+0x58/0x110
seq_read+0x41c/0x620
__vfs_read+0x3c/0x70
vfs_read+0xbc/0x1a0
ksys_read+0x7c/0x140
system_call+0x5c/0x70
kmemleak: Kernel memory leak detector disabled
kmemleak: Object 0xc000201cc8000000 (size 13757317120):
kmemleak: comm "swapper/0", pid 0, jiffies 4294937297
kmemleak: min_count = -1
kmemleak: count = 0
kmemleak: flags = 0x5
kmemleak: checksum = 0
kmemleak: backtrace:
cma_declare_contiguous+0x2a4/0x3b0
kvm_cma_reserve+0x11c/0x134
setup_arch+0x300/0x3f8
start_kernel+0x9c/0x6e8
start_here_common+0x1c/0x4b0
kmemleak: Automatic memory scanning thread ended
[cai@xxxxxx: use is_migrate_cma_page() and update commit log]
Link: http://lkml.kernel.org/r/20190416170510.20048-1-cai@xxxxxx
Link: http://lkml.kernel.org/r/20190413002623.8967-1-cai@xxxxxx
Signed-off-by: Qian Cai <cai@xxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
mm/page_alloc.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 318ef6ccdb3b..eedb57f9b40b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7945,7 +7945,10 @@ void *__init alloc_large_system_hash(const char *tablename,
bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
int migratetype, int flags)
{
- unsigned long pfn, iter, found;
+ unsigned long found;
+ unsigned long iter = 0;
+ unsigned long pfn = page_to_pfn(page);
+ const char *reason = "unmovable page";
/*
* TODO we could make this much more efficient by not checking every
@@ -7955,17 +7958,20 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
* can still lead to having bootmem allocations in zone_movable.
*/
- /*
- * CMA allocations (alloc_contig_range) really need to mark isolate
- * CMA pageblocks even when they are not movable in fact so consider
- * them movable here.
- */
- if (is_migrate_cma(migratetype) &&
- is_migrate_cma(get_pageblock_migratetype(page)))
- return false;
+ if (is_migrate_cma_page(page)) {
+ /*
+ * CMA allocations (alloc_contig_range) really need to mark
+ * isolate CMA pageblocks even when they are not movable in fact
+ * so consider them movable here.
+ */
+ if (is_migrate_cma(migratetype))
+ return false;
+
+ reason = "CMA page";
+ goto unmovable;
+ }
- pfn = page_to_pfn(page);
- for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) {
+ for (found = 0; iter < pageblock_nr_pages; iter++) {
unsigned long check = pfn + iter;
if (!pfn_valid_within(check))
@@ -8045,7 +8051,7 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
unmovable:
WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
if (flags & REPORT_FAILURE)
- dump_page(pfn_to_page(pfn+iter), "unmovable page");
+ dump_page(pfn_to_page(pfn + iter), reason);
return true;
}
--
2.20.1
