Re: [PATCH 4/5] mm: shmem: keep inode in swaplist when failed to allocate swap entry in shmem_writepage()

[Kemeng Shi <shikemeng@huaweicloud.com>]

on 5/14/2025 5:31 PM, Baolin Wang wrote:
> 
> 
> On 2025/5/15 00:50, Kemeng Shi wrote:
>> Even if we fail to allocate a swap entry, the inode might have previously
>> allocated entry and we might take inode containing swap entry off swaplist.
>> As a result, try_to_unuse() may enter a potential dead loop to repeatedly
>> look for inode and clean it's swap entry.
>> Address this by keeping inode in swaplist even if we fail to allocate
>> swap entry as it does not pose significant problem to keep inode without
>> swap entry in swaplist.
>>
>> Fixes: b487a2da3575b ("mm, swap: simplify folio swap allocation")
>> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
>> ---
>>   mm/shmem.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 0fed94c2bc09..dfd2f730833c 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -1651,8 +1651,6 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
>>           BUG_ON(folio_mapped(folio));
>>           return swap_writepage(&folio->page, wbc);
>>       }
>> -
>> -    list_del_init(&info->swaplist);
> 
> If 'info->swapped' is 0, we can still remove it?
> 
Sure, both approaches are acceptable to me: either keep it in list unconditionlly as it was done in old
behavior, or remove it if it's info->swapped is 0.