Re: [PATCH v3 2/3] mm/truncate: align truncation boundaries to mapping minimum folio order

[sashiko-bot@kernel.org]

> From: Zhang Yi <yi.zhang@huawei.com>
> 
> When the mapping has a non-zero minimum folio order (min_order),
> folio_split() stops at min_order instead of order 0, so the sub-folio
> containing a split point stays aligned to 1 << min_order rather than to
> a single page. The original boundaries were based on page granularity,
> so either boundary could land inside the min_order chunk at its edge,
> and the truncation loop would drop that whole chunk, valid out-of-range
> tail included.
> 
> For example, a 64K (order-4) folio with min_order = 2 (16K) punched from
> offset 0 to 36K:
> 
>   split @p0 -> [p0-p3, p4-p7, p8-p15]         # non-uniform, min_order
>   folio2 = p8-p15           # straddles: p8 in range, p9-p15 tail valid
> [ ... ]
> 
> Reported-by: Joanne Koong <joannelkoong@gmail.com>
> Link: https://lore.kernel.org/linux-mm/CAJnrk1bQYUe6+1ryyJur5EEnZYrC+_5AYsy=OWzVRgD4202y1g@mail.gmail.com/
> Fixes: e220917fa5077 ("mm: split a folio in minimum folio order chunks")
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260916092450.654408-1-yi.zhang@huaweicloud.com?part=2