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Date:   Fri, 01 Sep 2023 16:46:31 +0000
In-Reply-To: <f7aaf097-6f83-0ee9-e16d-713d392b2299@linux.intel.com> (message
 from Binbin Wu on Fri, 1 Sep 2023 11:45:43 +0800)
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Subject: Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for
 guest-specific backing memory
From:   Ackerley Tng <ackerleytng@google.com>
To:     Binbin Wu <binbin.wu@linux.intel.com>
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Binbin Wu <binbin.wu@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
folio.

> <snip>