linux-kernel - Re: [RFC PATCH] xen/privcmd: Convert get_user_pages*() to pin_user

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Date:   Mon, 22 Jun 2020 15:25:38 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Souptick Joarder <jrdr.linux@...il.com>
Cc:     John Hubbard <jhubbard@...dia.com>,
        Juergen Gross <jgross@...e.com>, sstabellini@...nel.org,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        paul@....org
Subject: Re: [RFC PATCH] xen/privcmd: Convert get_user_pages*() to
 pin_user_pages*()

On 6/22/20 3:28 PM, Souptick Joarder wrote:
> On Tue, Jun 23, 2020 at 12:40 AM Boris Ostrovsky
> <boris.ostrovsky@...cle.com> wrote:
>> On 6/22/20 2:52 PM, Souptick Joarder wrote:
>>> I read the code again. I think, this check is needed to handle a scenario when
>>> lock_pages() return -ENOSPC. Better to keep this check. Let me post v2 of this
>>> RFC for a clear view.
>>
>> Actually, error handling seems to be somewhat broken here. If
>> lock_pages() returns number of pinned pages then that's what we end up
>> returning from privcmd_ioctl_dm_op(), all the way to user ioctl(). Which
>> I don't think is right, we should return proper (negative) error.
>>
> What -ERRNO is more appropriate here ? -ENOSPC ?


You can simply pass along error code that get_user_pages_fast() returned.


-boris