mm, page_owner: dump page owner info from dump_page()
The page_owner mechanism is useful for dealing with memory leaks. By
reading /sys/kernel/debug/page_owner one can determine the stack traces
leading to allocations of all pages, and find e.g. a buggy driver.
This information might be also potentially useful for debugging, such as
the VM_BUG_ON_PAGE() calls to dump_page(). So let's print the stored
info from dump_page().
Example output:
page:ffffea000292f1c0 count:1 mapcount:0 mapping:ffff8800b2f6cc18 index:0x91d
flags: 0x1fffff8001002c(referenced|uptodate|lru|mappedtodisk)
page dumped because: VM_BUG_ON_PAGE(1)
page->mem_cgroup:ffff8801392c5000
page allocated via order 0, migratetype Movable, gfp_mask 0x24213ca(GFP_HIGHUSER_MOVABLE|__GFP_COLD|__GFP_NOWARN|__GFP_NORETRY)
[<ffffffff811682c4>] __alloc_pages_nodemask+0x134/0x230
[<ffffffff811b40c8>] alloc_pages_current+0x88/0x120
[<ffffffff8115e386>] __page_cache_alloc+0xe6/0x120
[<ffffffff8116ba6c>] __do_page_cache_readahead+0xdc/0x240
[<ffffffff8116bd05>] ondemand_readahead+0x135/0x260
[<ffffffff8116be9c>] page_cache_async_readahead+0x6c/0x70
[<ffffffff811604c2>] generic_file_read_iter+0x3f2/0x760
[<ffffffff811e0dc7>] __vfs_read+0xa7/0xd0
page has been migrated, last migrate reason: compaction
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_owner.c b/mm/page_owner.c
index a57068c..44ad1f0 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -183,6 +183,31 @@
return -ENOMEM;
}
+void __dump_page_owner(struct page *page)
+{
+ struct page_ext *page_ext = lookup_page_ext(page);
+ struct stack_trace trace = {
+ .nr_entries = page_ext->nr_entries,
+ .entries = &page_ext->trace_entries[0],
+ };
+ gfp_t gfp_mask = page_ext->gfp_mask;
+ int mt = gfpflags_to_migratetype(gfp_mask);
+
+ if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
+ pr_alert("page_owner info is not active (free page?)\n");
+ return;
+ }
+
+ pr_alert("page allocated via order %u, migratetype %s, "
+ "gfp_mask %#x(%pGg)\n", page_ext->order,
+ migratetype_names[mt], gfp_mask, &gfp_mask);
+ print_stack_trace(&trace, 0);
+
+ if (page_ext->last_migrate_reason != -1)
+ pr_alert("page has been migrated, last migrate reason: %s\n",
+ migrate_reason_names[page_ext->last_migrate_reason]);
+}
+
static ssize_t
read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{