linux-kernel - RE: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin

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Date:   Thu, 7 Jul 2022 08:42:28 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "corbet@....net" <corbet@....net>,
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        "Wang, Zhi A" <zhi.a.wang@...el.com>,
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CC:     "jchrist@...ux.ibm.com" <jchrist@...ux.ibm.com>,
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Subject: RE: [RFT][PATCH v2 1/9] vfio: Make vfio_unpin_pages() return void

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Wednesday, July 6, 2022 2:28 PM
> 
> There's only one caller that checks its return value with a WARN_ON_ONCE,
> while all other callers do not check return value at all. So simplify the
> API to return void by embedding similar WARN_ON_ONCEs.

While this change keeps the similar effect as before it leads to different
policy for same type of errors between pin and unpin paths:

e.g.

vfio_unpin_pages():
	if (WARN_ON_ONCE(!user_pfn || !npage || !vfio_assert_device_open(device)))
		return;

vfio_pin_pages():
	if (!user_pfn || !phys_pfn || !npage ||
	    !vfio_assert_device_open(device))
		return -EINVAL;

It sounds a bit weird when reading related code...