Re: [PATCH] mm/shmem: drop the second folio batch from shmem_undo_range()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 11/13/26 04:39, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found no new issues
> in this patch, but noticed 1 related pre-existing issue it does not
> introduce:
> - [Critical] mm/shmem: skipped boundary zeroing on swapin failure in
>   shmem_undo_range() [1]
> --
> 
> commit 785bd3384006f8bb06c3c8f9b1b5d455eba3d449
> Author: Qiliang Yuan <qiliang.yuan@linux.dev>
> 
> mm/shmem: drop the second folio batch from shmem_undo_range()
> 
> This commit removes the second folio_batch from shmem_undo_range() by
> passing fbatch directly to delete_from_page_cache_batch() after removing
> swap entries, and using truncate_inode_folio() when undoing a failed
> fallocate().
> 
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 156469423a866..5bcbdd6078a73 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -1352,9 +1352,6 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,
>>  	index = start;
>>  	while (index < end && find_lock_entries(mapping, &index, end - 1,
>>  			&fbatch, indices)) {
>> -		struct folio_batch remove;
>> -
>> -		folio_batch_init(&remove);
>>  		for (i = 0; i < folio_batch_count(&fbatch); i++) {
>>  			folio = fbatch.folios[i];
>>  
>> @@ -1366,13 +1363,14 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,
>>  				continue;
>>  			}
>>  
>> -			if (!unfalloc || !folio_test_uptodate(folio)) {
>> +			if (!unfalloc)
>>  				truncate_cleanup_folio(folio);
>> -				folio_batch_add(&remove, folio);
>> -			}
>> +			else if (!folio_test_uptodate(folio))
>> +				truncate_inode_folio(mapping, folio);
>>  		}
>> -		delete_from_page_cache_batch(mapping, &remove);
>>  		folio_batch_remove_exceptionals(&fbatch);
>> +		if (!unfalloc)
>> +			delete_from_page_cache_batch(mapping, &fbatch);
>>  		for (i = 0; i < folio_batch_count(&fbatch); i++)
>>  			folio_unlock(fbatch.folios[i]);
>>  		folio_batch_release(&fbatch);
> 
> [Severity: Critical]
> This problem wasn't introduced by this patch, but can shmem_undo_range()
> leave partial boundary ranges unzeroed when swapping in a boundary folio
> fails [1]?

Roman, why is Sashiko back with these preexisting things that keep distracting
people in unreasonable ways?

Turn that feature off for MM please. Let all preexisting stuff go to the
maintainer-accessible, where we will work through them in a controlled way.

The least we need right now is getting bombarded with more of these things.

-- 
Cheers,

David