From: Qian Cai cai@lca.pw
[ 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@lca.pw: use is_migrate_cma_page() and update commit log] Link: http://lkml.kernel.org/r/20190416170510.20048-1-cai@lca.pw Link: http://lkml.kernel.org/r/20190413002623.8967-1-cai@lca.pw Signed-off-by: Qian Cai cai@lca.pw Acked-by: Michal Hocko mhocko@suse.com Acked-by: Vlastimil Babka vbabka@suse.cz Reviewed-by: Oscar Salvador osalvador@suse.de Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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; }