On 2021/4/25 12:20, Huang, Ying wrote:
> Miaohe Lin <linmiaohe@xxxxxxxxxx> writes:
>
>> On 2021/4/25 11:07, Huang, Ying wrote:
>>> I think it's better to put_swap_device() just before returning from the
>>> function. It's not a big issue to slow down swapoff() a little. And
>>> this will make the logic easier to be understood.
>>>
>>
>> shmem_swapin_page() already has a methed, i.e. locked page, to prevent races. I was intended
>> to not mix with that. But your suggestion is good as this will make the logic easier to be
>> understood.
>>
>> Just to make sure, is this what you mean? Many thanks!
>
> Yes. Just a minor comment.
>
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 26c76b13ad23..737e5b3200c3 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -1696,6 +1696,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
>> struct address_space *mapping = inode->i_mapping;
>> struct shmem_inode_info *info = SHMEM_I(inode);
>> struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm;
>> + struct swap_info_struct *si;
>> struct page *page;
>> swp_entry_t swap;
>> int error;
>> @@ -1704,6 +1705,12 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
>> swap = radix_to_swp_entry(*pagep);
>> *pagep = NULL;
>>
>> + /* Prevent swapoff from happening to us. */
>> + si = get_swap_device(swap);
>> + if (unlikely(!si)) {
>
> I don't think it's necessary to use unlikely() here.
>
Will do in next version. Thanks!
> Best Regards,
> Huang, Ying
>
>> + error = EINVAL;
>> + goto failed;
>> + }
>> /* Look it up and read it in.. */
>> page = lookup_swap_cache(swap, NULL, 0);
>> if (!page) {
>> @@ -1765,6 +1772,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
>> swap_free(swap);
>>
>> *pagep = page;
>> + if (si)
>> + put_swap_device(si);
>> return 0;
>> failed:
>> if (!shmem_confirm_swap(mapping, index, swap))
>> @@ -1775,6 +1784,9 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
>> put_page(page);
>> }
>>
>> + if (si)
>> + put_swap_device(si);
>> +
>> return error;
>> }
>>
>>> Best Regards,
>>> Huang, Ying
>>>
> .
>
