Re: [PATCH v3 3/3] hwpoison, memory_hotplug: lock folio before unmap hwpoisoned folio

[Miaohe Lin <linmiaohe@huawei.com>]

On 2025/2/17 9:43, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@huawei.com>
> 
> Commit b15c87263a69 ("hwpoison, memory_hotplug: allow hwpoisoned pages to
> be offlined) add page poison checks in do_migrate_range in order to make
> offline hwpoisoned page possible by introducing isolate_lru_page and
> try_to_unmap for hwpoisoned page. However folio lock must be held before
> calling try_to_unmap. Add it to fix this problem.
> 
> Warning will be produced if folio is not locked during unmap:
> 
>   ------------[ cut here ]------------
>   kernel BUG at ./include/linux/swapops.h:400!
>   Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
>   Modules linked in:
>   CPU: 4 UID: 0 PID: 411 Comm: bash Tainted: G        W          6.13.0-rc1-00016-g3c434c7ee82a-dirty #41
>   Tainted: [W]=WARN
>   Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
>   pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>   pc : try_to_unmap_one+0xb08/0xd3c
>   lr : try_to_unmap_one+0x3dc/0xd3c
>   Call trace:
>    try_to_unmap_one+0xb08/0xd3c (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
>   Code: f9407be0 b5fff320 d4210000 17ffff97 (d4210000)
>   ---[ end trace 0000000000000000 ]---
> 
> Fixes: b15c87263a69 ("hwpoison, memory_hotplug: allow hwpoisoned pages to be offlined")
> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> Acked-by: David Hildenbrand <david@redhat.com>

Acked-by: Miaohe Lin <linmiaohe@huawei.com>

Thanks.
.