[PATCH 2/2] mm, page_owner: provide symbolic page flags and gfp_flags

Vlastimil Babka
2015-11-30T16:11:00Z

With the new format strings for flags, we can now provide symbolic page and gfp
flags in the /sys/kernel/debug/page_owner file. This replaces the positional
printing of page flags as single letters, which might have looked nicer, but
was limited to a subset of flags, and required the user to remember the
letters.

Example of the adjusted format:

Page allocated via order 0, mask 0x24213ca(GFP_HIGHUSER_MOVABLE|GFP_COLD|GFP_NOWARN|GFP_NORETRY)
PFN 674308 type Movable Block 1317 type Movable Flags 0x1fffff80010068(uptodate|lru|active|mappedtodisk)
[<ffffffff81164e9a>] __alloc_pages_nodemask+0x15a/0xa30
[<ffffffff811ab938>] alloc_pages_current+0x88/0x120
[<ffffffff8115bc46>] __page_cache_alloc+0xe6/0x120
[<ffffffff81168b9b>] __do_page_cache_readahead+0xdb/0x200
[<ffffffff81168df5>] ondemand_readahead+0x135/0x260
[<ffffffff81168f8c>] page_cache_async_readahead+0x6c/0x70
[<ffffffff8115d5f8>] generic_file_read_iter+0x378/0x590
[<ffffffff811d12a7>] __vfs_read+0xa7/0xd0
Page has been migrated, last migrate reason: compaction

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/page_owner.c | 19 ++++---------------
1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index ff862b6d12da..421765a53c68 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -135,8 +135,8 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
return -ENOMEM;

ret = snprintf(kbuf, count,
- "Page allocated via order %u, mask 0x%x\n",
- page_ext->order, page_ext->gfp_mask);
+ "Page allocated via order %u, mask %pgg\n",
+ page_ext->order, &page_ext->gfp_mask);

if (ret >= count)
goto err;
@@ -145,23 +145,12 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
pageblock_mt = get_pfnblock_migratetype(page, pfn);
page_mt = gfpflags_to_migratetype(page_ext->gfp_mask);
ret += snprintf(kbuf + ret, count - ret,
- "PFN %lu type %s Block %lu type %s Flags %s%s%s%s%s%s%s%s%s%s%s%s\n",
+ "PFN %lu type %s Block %lu type %s Flags %pgp\n",
pfn,
migratetype_names[page_mt],
pfn >> pageblock_order,
migratetype_names[pageblock_mt],
- PageLocked(page) ? "K" : " ",
- PageError(page) ? "E" : " ",
- PageReferenced(page) ? "R" : " ",
- PageUptodate(page) ? "U" : " ",
- PageDirty(page) ? "D" : " ",
- PageLRU(page) ? "L" : " ",
- PageActive(page) ? "A" : " ",
- PageSlab(page) ? "S" : " ",
- PageWriteback(page) ? "W" : " ",
- PageCompound(page) ? "C" : " ",
- PageSwapCache(page) ? "B" : " ",
- PageMappedToDisk(page) ? "M" : " ");
+ &page->flags);

if (ret >= count)
goto err;
--
2.6.3