Re: [PATCH -V6 06/21] swap: Support PMD swap mapping when splitting huge PMD

[Huang\, Ying]

Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> writes:

> On Wed, Oct 10, 2018 at 03:19:09PM +0800, Huang Ying wrote:
>> +#ifdef CONFIG_THP_SWAP
>> +/*
>> + * The corresponding page table shouldn't be changed under us, that
>> + * is, the page table lock should be held.
>> + */
>> +int split_swap_cluster_map(swp_entry_t entry)
>> +{
>> +	struct swap_info_struct *si;
>> +	struct swap_cluster_info *ci;
>> +	unsigned long offset = swp_offset(entry);
>> +
>> +	VM_BUG_ON(!IS_ALIGNED(offset, SWAPFILE_CLUSTER));
>> +	si = _swap_info_get(entry);
>> +	if (!si)
>> +		return -EBUSY;
>
> I think this return value doesn't get used anywhere?

Yes.  And the error is only possible if page table is corrupted.  So
maybe add a VM_BUG_ON() in it caller __split_huge_swap_pmd()?

Best Regards,
Huang, Ying