linux-kernel - Re: [RFC PATCH 03/19] drivers/vdpa: Convert vdpa to use the new vm

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Message-ID: <Y8/sr4SfnuoXxApR@nvidia.com>
Date:   Tue, 24 Jan 2023 10:35:27 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Alistair Popple <apopple@...dia.com>
Cc:     linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, jhubbard@...dia.com,
        tjmercier@...gle.com, hannes@...xchg.org, surenb@...gle.com,
        mkoutny@...e.com, daniel@...ll.ch,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [RFC PATCH 03/19] drivers/vdpa: Convert vdpa to use the new
 vm_structure

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