From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Gunthorpe <jgg-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC PATCH 03/19] drivers/vdpa: Convert vdpa to use the new
 vm_structure
Date: Tue, 24 Jan 2023 10:35:27 -0400
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To: Alistair Popple <apopple-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, jhubbard-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, tjmercier-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, surenb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, mkoutny-IBi9RG/b67k@public.gmane.org, daniel-/w4YWyX8dFk@public.gmane.org, "Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Jason Wang <jasowang-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org

On Tue, Jan 24, 2023 at 04:42:32PM +1100, Alistair Popple wrote:
> @@ -990,8 +989,8 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
>  
>  	mmap_read_lock(current->mm);
>  
> -	lock_limit = PFN_DOWN(rlimit(RLIMIT_MEMLOCK));
> -	if (npages + atomic64_read(&current->mm->pinned_vm) > lock_limit)
> +	vm_account_init_current(&umem->vm_account);
> +	if (vm_account_pinned(&umem->vm_account, npages))
>  		goto out;
>  
>  	pinned = pin_user_pages(uaddr, npages, FOLL_LONGTERM | FOLL_WRITE,
> @@ -1006,22 +1005,21 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
>  	if (ret)
>  		goto out;
>  
> -	atomic64_add(npages, &current->mm->pinned_vm);

Mention in the commit message that this fixes a bug where vdpa would
race the update of mm->pinned_vm and might go past the limit.

Jason