linux-kernel - Re: [RFC PATCH 26/39] KVM: guest_memfd: Track faultability within a struct kvm_gmem

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Message-ID: <Z74p8-l6BhOmR1B_@x1.local>
Date: Tue, 25 Feb 2025 15:37:07 -0500
From: Peter Xu <peterx@...hat.com>
To: Ackerley Tng <ackerleytng@...gle.com>
Cc: tabba@...gle.com, quic_eberman@...cinc.com, roypat@...zon.co.uk,
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	linux-kselftest@...r.kernel.org, linux-fsdevel@...ck.org
Subject: Re: [RFC PATCH 26/39] KVM: guest_memfd: Track faultability within a
 struct kvm_gmem_private

On Tue, Sep 10, 2024 at 11:43:57PM +0000, Ackerley Tng wrote:
> @@ -1079,12 +1152,20 @@ static struct inode *kvm_gmem_inode_make_secure_inode(const char *name,
>  	if (err)
>  		goto out;
>  
> +	err = -ENOMEM;
> +	private = kzalloc(sizeof(*private), GFP_KERNEL);
> +	if (!private)
> +		goto out;
> +
>  	if (flags & KVM_GUEST_MEMFD_HUGETLB) {
> -		err = kvm_gmem_hugetlb_setup(inode, size, flags);
> +		err = kvm_gmem_hugetlb_setup(inode, private, size, flags);
>  		if (err)
> -			goto out;
> +			goto free_private;
>  	}
>  
> +	xa_init(&private->faultability);
> +	inode->i_mapping->i_private_data = private;
> +
>  	inode->i_private = (void *)(unsigned long)flags;

Looks like inode->i_private isn't used before this series; the flags was
always zero before anyway.  Maybe it could keep kvm_gmem_inode_private
instead? Then make the flags be part of the struct.

It avoids two separate places (inode->i_mapping->i_private_data,
inode->i_private) to store gmem private info.

>  	inode->i_op = &kvm_gmem_iops;
>  	inode->i_mapping->a_ops = &kvm_gmem_aops;
> @@ -1097,6 +1178,8 @@ static struct inode *kvm_gmem_inode_make_secure_inode(const char *name,
>  
>  	return inode;
>  
> +free_private:
> +	kfree(private);
>  out:
>  	iput(inode);
>  
> -- 
> 2.46.0.598.g6f2099f65c-goog
> 

-- 
Peter Xu