Re: [PATCH 3/3] btrfs: Avoid live-lock in search_ioctl() on hardware with sub-page faults

Catalin Marinas
2021-11-29T15:46:05Z

On Sat, Nov 27, 2021 at 07:05:39PM +0100, Andreas Gruenbacher wrote:
> Maybe you want to add this though:
>
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2202,3 +2202,3 @@ static noinline int search_ioctl(struct inode *inode,
> unsigned long sk_offset = 0;
> - char __user *fault_in_addr;
> + char __user *fault_in_addr, *end;
>
> @@ -2230,6 +2230,6 @@ static noinline int search_ioctl(struct inode *inode,
> fault_in_addr = ubuf;
> + end = ubuf + *buf_size;
> while (1) {
> ret = -EFAULT;
> - if (fault_in_writeable(fault_in_addr,
> - *buf_size - (fault_in_addr - ubuf)))
> + if (fault_in_writeable(fault_in_addr, end - fault_in_addr))
> break;

It looks like *buf_size is updated inside copy_to_sk(), so I'll move the
end update inside the loop.

--
Catalin