Re: [PATCH 4/4] mm/memory-failure: Fall back to vma_address() when ->notify_failure() fails

[Miaohe Lin <linmiaohe@huawei.com>]

On 2022/8/30 11:57, Dan Williams wrote:
> Miaohe Lin wrote:
>> On 2022/8/27 1:18, Dan Williams wrote:
>>> In the case where a filesystem is polled to take over the memory failure
>>> and receives -EOPNOTSUPP it indicates that page->index and page->mapping
>>> are valid for reverse mapping the failure address. Introduce
>>> FSDAX_INVALID_PGOFF to distinguish when add_to_kill() is being called
>>> from mf_dax_kill_procs() by a filesytem vs the typical memory_failure()
>>> path.
>>
>> Thanks for fixing.
>> I'm sorry but I can't find the bug report email. 
> 
> Report is here:
> 
> https://lore.kernel.org/all/63069db388d43_1b3229426@dwillia2-xfh.jf.intel.com.notmuch/
> 
>> Do you mean mf_dax_kill_procs() can pass an invalid pgoff to the
>> add_to_kill()? 
> 
> No, the problem is that ->notify_failure() returns -EOPNOTSUPP so
> memory_failure_dev_pagemap() falls back to mf_generic_kill_procs().
> However, mf_generic_kill_procs() end up passing '0' for fsdax_pgoff from
> collect_procs_file() to add_to_kill(). A '0' for fsdax_pgoff results in
> vma_pgoff_address() returning -EFAULT which causes the VM_BUG_ON() in
> dev_pagemap_mapping_shift().

Many thanks for your explanation.

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

Thanks,
Miaohe Lin