mm: memory-failure: update ttu flag inside unmap_poisoned_folio

In the Linux kernel, the following vulnerability has been resolved:

mm: memory-failure: update ttu flag inside unmap_poisoned_folio

Patch series "mm: memory_failure: unmap poisoned folio during migrate

properly", v3.

Fix two bugs during folio migration if the folio is poisoned.

This patch (of 3):

Commit 6da6b1d4a7df ("mm/hwpoison: convert TTU_IGNORE_HWPOISON to

TTU_HWPOISON") introduce TTU_HWPOISON to replace TTU_IGNORE_HWPOISON in

order to stop send SIGBUS signal when accessing an error page after a

memory error on a clean folio. However during page migration, anon folio

must be set with TTU_HWPOISON during unmap_*(). For pagecache we need

some policy just like the one in hwpoison_user_mappings to set this flag.

So move this policy from hwpoison_user_mappings to unmap_poisoned_folio to

handle this warning properly.

Warning will be produced during unamp poison folio with the following log:

------------[ cut here ]------------

WARNING: CPU: 1 PID: 365 at mm/rmap.c:1847 try_to_unmap_one+0x8fc/0xd3c

Modules linked in:

CPU: 1 UID: 0 PID: 365 Comm: bash Tainted: G W 6.13.0-rc1-00018-gacdb4bbda7ab #42

Tainted: [W]=WARN

Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015

pstate: 20400005 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)

pc : try_to_unmap_one+0x8fc/0xd3c

lr : try_to_unmap_one+0x3dc/0xd3c

Call trace:

try_to_unmap_one+0x8fc/0xd3c (P)

try_to_unmap_one+0x3dc/0xd3c (L)

rmap_walk_anon+0xdc/0x1f8

rmap_walk+0x3c/0x58

try_to_unmap+0x88/0x90

unmap_poisoned_folio+0x30/0xa8

do_migrate_range+0x4a0/0x568

offline_pages+0x5a4/0x670

memory_block_action+0x17c/0x374

memory_subsys_offline+0x3c/0x78

device_offline+0xa4/0xd0

state_store+0x8c/0xf0

dev_attr_store+0x18/0x2c

sysfs_kf_write+0x44/0x54

kernfs_fop_write_iter+0x118/0x1a8

vfs_write+0x3a8/0x4bc

ksys_write+0x6c/0xf8

__arm64_sys_write+0x1c/0x28

invoke_syscall+0x44/0x100

el0_svc_common.constprop.0+0x40/0xe0

do_el0_svc+0x1c/0x28

el0_svc+0x30/0xd0

el0t_64_sync_handler+0xc8/0xcc

el0t_64_sync+0x198/0x19c

---[ end trace 0000000000000000 ]---

[[email protected]: unmap_poisoned_folio(): remove shadowed local `mapping', per Miaohe]