"alloc_tag was not set" when running mm/ksft_hmm.sh

"alloc_tag was not set" when running mm/ksft_hmm.sh

[Zenghui Yu]

Hi all,

Running mm/ksft_hmm.sh triggers the following splat:

 ------------[ cut here ]------------
 alloc_tag was not set
 WARNING: ./include/linux/alloc_tag.h:164 at ___free_pages+0x2a0/0x2d0,
CPU#5: hmm-tests/2020
 Modules linked in: test_hmm rfkill drm backlight fuse
 CPU: 5 UID: 0 PID: 2020 Comm: hmm-tests Kdump: loaded Not tainted
7.1.0-rc2-00099-gadc1e5c6203c-dirty #285 PREEMPT
 Hardware name: QEMU QEMU Virtual Machine, BIOS
edk2-stable202408-prebuilt.qemu.org 08/13/2024
 pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
 pc : ___free_pages+0x2a0/0x2d0
 lr : ___free_pages+0x2a0/0x2d0
 sp : ffff80008345b530
 x29: ffff80008345b530 x28: ffff80008345b700 x27: ffffffffbfff8040
 x26: ffff0000c41cb360 x25: ffff0000c0c64008 x24: ffff800081aae400
 x23: 05ffff0000000200 x22: 0000000000000000 x21: 0000000000000000
 x20: fffffdffc5f20040 x19: 0000000000000000 x18: fffffffffffe7c78
 x17: 0000000000000000 x16: 0000000000000000 x15: fffffffffffe7c98
 x14: 00000000000001d1 x13: ffff8000818f3d58 x12: 0000000000000573
 x11: fffffffffffe7c98 x10: ffff80008194bd58 x9 : 3ffffffffffff000
 x8 : ffff8000818f3d58 x7 : ffff80008194bd58 x6 : 0000000000000000
 x5 : ffff0001fedb1088 x4 : 0000000000000001 x3 : 0000000000000000
 x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000c7f58000
 Call trace:
  ___free_pages+0x2a0/0x2d0 (P)
  __free_pages+0x14/0x20
  dmirror_devmem_free+0x13c/0x158 [test_hmm]
  free_zone_device_folio+0x144/0x1e4
  __folio_put+0x124/0x130
  free_folio_and_swap_cache+0xa8/0xcc
  __folio_split+0x664/0x7fc
  split_folio_to_list+0x50/0x5c
  migrate_vma_split_folio+0x13c/0x25c
  migrate_vma_collect_pmd+0xed4/0xf68
  walk_pgd_range+0x598/0x9a0
  __walk_page_range+0x90/0x1a0
  walk_page_range_mm_unsafe+0x194/0x20c
  walk_page_range+0x20/0x2c
  migrate_vma_setup+0x18c/0x224
  dmirror_devmem_fault+0x188/0x2b8 [test_hmm]
  do_swap_page+0x1458/0x185c
  __handle_mm_fault+0x85c/0x1ba0
  handle_mm_fault+0xb0/0x290
  do_page_fault+0x1f8/0x6f8
  do_translation_fault+0x60/0x6c
  do_mem_abort+0x44/0x94
  el0_da+0x30/0xdc
  el0t_64_sync_handler+0xd0/0xe4
  el0t_64_sync+0x198/0x19c
 ---[ end trace 0000000000000000 ]---
 lib/test_hmm.c:705 module test_hmm func:dmirror_devmem_alloc_page has
16744448 allocated at module unload


It was tested on kernel built with arm64's virt.config and

+CONFIG_ZONE_DEVICE=y
+CONFIG_DEVICE_PRIVATE=y
+CONFIG_TEST_HMM=m
+CONFIG_MEM_ALLOC_PROFILING=y
+CONFIG_MEM_ALLOC_PROFILING_DEBUG=y

Thanks,
Zenghui