Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory

[Ackerley Tng]

Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> writes:

> <snip>
>
>>
>> I'm not sure whose refcount the folio_put() in kvm_gmem_allocate() is
>> dropping though:
>>
>> + The refcount for the filemap depends on whether this is a hugepage or
>>    not, but folio_put() strictly drops a refcount of 1.
>> + The refcount for the lru list is just 1, but doesn't the page still
>>    remain in the lru list?
>
> I guess the refcount drop here is the one get on the fresh allocation.
> Now the filemap has grabbed the folio, so the lifecycle of the folio now 
> is decided by the filemap/inode?
>

This makes sense! So folio_put() here is saying, I'm not using this
folio anymore, but the filemap and the lru list are stil using the
folio.

> <snip>