Re: [QUESTION] xas_reload() in iter_xarray_populate_pages()

[David Hildenbrand <david@redhat.com>]

On 17.06.25 07:10, Dev Jain wrote:
> 
> On 26/05/25 12:05 pm, Dev Jain wrote:
>> Hello all,
>>
>> After doing an xas_load() and xas_retry(), we take neither a reference nor a lock
>> on the folio, and we do an xas_reload(). Is this just to reduce the time window
>> for a race?
>>
>> If the above is true, then, there is a negligible window between xas_load() and
>> xas_reload(), because only xas_retry() exists between them, so why to even reload()?
>>
>> Thanks,
>> Dev
> 
> I do not completely remember our discussion in THP Cabal; I recall David Howells maybe
> saying that the folios are already locked, so it is safe to do xas_load and then do
> a folio_get()? Even if we remove the redundant xas_reload(), I still don't understand
> why we won't need xas_reload() at least after folio_get()?

I think the points where

(a) this should go all away soon

(b) there is the expectation that the folios cannot get truncated
     concurrently. So we can do an unconditional folio_get(), don't have
     to check folio->mapping etc.

(c) The xas_reload() seems unnecessary and can be dropped.

-- 
Cheers,

David / dhildenb