Re: [PATCH v2 2/2] mm/memory_hotplug: fix hwpoisoned large folio handling in do_migrate_range

[David Hildenbrand <david@redhat.com>]

On 14.07.25 17:09, Pankaj Raghav (Samsung) wrote:
>>>>> So we will need to take care of madvise cold or pageout case?
>>>>>
>>>>> Hi Matthew, Pankaj, and Luis,
>>>>>
>>>>> Is it possible to partially map a min-order folio in a fs with LBS? Based on my
>>>>
>>>> Typically, FSs match the min order with the blocksize of the filesystem.
>>>> As a filesystem block is the smallest unit of data that the filesystem uses
>>>> to store file data on the disk, we cannot partially map them.
>>>>
>>>> So if I understand your question correctly, the answer is no.
>>
>> I'm confused. Shouldn't this be trivially possible?
>>
> Hmm, maybe I misunderstood the question?
> 
>> E.g., just mmap() a single page of such a file? Who would make that fail?
>>
> 
> My point was, even if you try to mmap a single page of a file, page
> cache will read the whole block (that corresponds to min order folio).
> 
> Technically we can mmap a single page of file, but FS will always read
> and write **at least** in min folio order chunks.

Okay, so it can be partially mapped into page tables :) What happens in 
the background (page cache management) is a different story

-- 
Cheers,

David / dhildenb