Re: [PATCH 1/7] mm: shmem: correctly pass alloced parameter to shmem_recalc_inode() to avoid WARN_ON()

[Kemeng Shi <shikemeng@huaweicloud.com>]

on 6/6/2025 3:57 AM, Andrew Morton wrote:
> On Fri,  6 Jun 2025 06:10:31 +0800 Kemeng Shi <shikemeng@huaweicloud.com> wrote:
> 
>> As noted in the comments, we need to release block usage for swap entry
>> which was replaced with poisoned swap entry. However, no block usage is
>> actually freed by calling shmem_recalc_inode(inode, -nr_pages, -nr_pages).
>> Instead, call shmem_recalc_inode(inode, 0, -nr_pages) can correctly release
>> the block usage.
>>
>> ...
>>
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -2145,7 +2145,7 @@ static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
>>  	 * won't be 0 when inode is released and thus trigger WARN_ON(i_blocks)
>>  	 * in shmem_evict_inode().
>>  	 */
>> -	shmem_recalc_inode(inode, -nr_pages, -nr_pages);
>> +	shmem_recalc_inode(inode, 0, -nr_pages);
>>  	swap_free_nr(swap, nr_pages);
>>  }
> 
> Huh, three years ago.  What do we think might be the userspace-visible
> runtime effects of this?
This could trigger WARN_ON(i_blocks) in shmem_evict_inode() as i_blocks
is supposed to be dropped in the quota free routine.
> 
>