ANDROID: mm: page_pinner: introduce failure_tracking feature

CMA allocation can fail by temporal page refcount increasement
by get_page API as well as get_user_pages friends.
However, since get_page is one of the most hot function, it is
hard to hook get_page to get callstack everytime due to
performance concern. Furthermore, get_page could be nested
multiple times so we couldn't track all of the pin sites on
limited space of page_pinner.

Thus, here approach is keep tracking of put_page callsite rather
than get_page once VM found the page migration failed.
It's based on assumption:

1. Since it's temporal page refcount, it could be released soon
   before overflowing dmesg log buffer
2. developer can find the pair of get_page by reviewing put_page.

By default, it's eanbled. If you want to disable it:

  echo 0 > $debugfs/page_pinner/failure_tracking

You can capture the tracking using:

  cat $debugfs/page_pinner/alloc_contig_failed

note: the example below is artificial:

Page pinned ts 386067292 us count 0
PFN 10162530 Block 9924 type Isolate Flags 0x800000000008000c(uptodate|dirty|swapbacked)
 __page_pinner_migration_failed+0x30/0x104
 putback_lru_page+0x90/0xac
 putback_movable_pages+0xc4/0x204
 __alloc_contig_migrate_range+0x290/0x31c
 alloc_contig_range+0x114/0x2bc
 cma_alloc+0x2d8/0x698
 cma_alloc_write+0x58/0xb8
 simple_attr_write+0xd4/0x124
 debugfs_attr_write+0x50/0xd8
 full_proxy_write+0x70/0xf8
 vfs_write+0x168/0x3a8
 ksys_write+0x7c/0xec
 __arm64_sys_write+0x20/0x30
 el0_svc_common+0xa4/0x180
 do_el0_svc+0x28/0x88
 el0_svc+0x14/0x24

Page pinned ts 385867394 us count 0
PFN 10162530 Block 9924 type Isolate Flags 0x800000000008000c(uptodate|dirty|swapbacked)
 __page_pinner_migration_failed+0x30/0x104
 __alloc_contig_migrate_range+0x200/0x31c
 alloc_contig_range+0x114/0x2bc
 cma_alloc+0x2d8/0x698
 cma_alloc_write+0x58/0xb8
 simple_attr_write+0xd4/0x124
 debugfs_attr_write+0x50/0xd8
 full_proxy_write+0x70/0xf8
 vfs_write+0x168/0x3a8
 ksys_write+0x7c/0xec
 __arm64_sys_write+0x20/0x30
 el0_svc_common+0xa4/0x180
 do_el0_svc+0x28/0x88
 el0_svc+0x14/0x24
 el0_sync_handler+0x88/0xec
 el0_sync+0x198/0x1c0

Bug: 183414571
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: Ie79902c18390eb9f320d823839bb9d9a7fdcdb31

include/linux/page_ext.h

@@ -22,6 +22,8 @@ enum page_ext_flags {
 #if defined(CONFIG_PAGE_PINNER)
 	/* page refcount was increased by GUP or follow_page(FOLL_GET) */
 	PAGE_EXT_GET,
+	/* page migration failed */
+	PAGE_EXT_PINNER_MIGRATION_FAILED,
 #endif
 #if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
 	PAGE_EXT_YOUNG,