Re: [PATCH 6.12.y 2/5] mm/damon/paddr: respect folio end for DAMOS actions except STAT

[sashiko-bot@kernel.org]

> A few functions for applying DAMOS actions including pageout, lru_[de]prio
> and migrate_{hot,cold} in DAMON physical address space operation set
> (paddr) collect folios of the given region by getting the folios of
> region-internal addresses.  Then, those functions apply the action to the
> collected folios at once.  The collection starts from the region start
> address and advances the address by the size of the folio of the address
> until it goes out of the region.  If the start address is in the middle of
> a large folio, and if the next folios are small, some of the next folios
> could be skipped.  Fix the issue by advancing the address to exactly the
> start address of the next folio.
> 
> The user impact is that DAMOS action is applied to less than expected
> amount of memory.  Given the best effort nature of DAMON, it is no big
> problem, but it is clearly a bug that is better to be fixed.
> 
> The issue was discovered [1] by Sashiko.
> 
> Link: https://lore.kernel.org/20260901131850.98037-4-sj@kernel.org
> Link: https://lore.kernel.org/20260517234112.89245-1-sj@kernel.org [1]
> Fixes: 3a06696305e7 ("mm/damon/ops: have damon_get_folio return folio even for tail pages")
> Signed-off-by: SJ Park <sj@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261108195145.115792-1-sj@kernel.org?part=2