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

Ackerley Tng ackerleytng at google.com
Sat Sep 2 02:46:31 AEST 2023

Binbin Wu <binbin.wu at linux.intel.com> 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

> <snip>

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