Re: [PATCH] UserfaultFD: Rename uffd_api.bits into .features

[Pavel Emelyanov <xemul@parallels.com>]

On 05/07/2015 04:42 PM, Andrea Arcangeli wrote:
> Hi Pavel,
> 
> On Thu, Apr 30, 2015 at 07:38:12PM +0300, Pavel Emelyanov wrote:
>> Hi,
>>
>> This is (seem to be) the minimal thing that is required to unblock
>> standard uffd usage from the non-cooperative one. Now more bits can
>> be added to the features field indicating e.g. UFFD_FEATURE_FORK and
>> others needed for the latter use-case.
>>
>> Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
> 
> Applied.
> 
> http://git.kernel.org/cgit/linux/kernel/git/andrea/aa.git/commit/?h=userfault&id=c2dee3384770a953cbad27b46854aa6fd13656c6
> http://git.kernel.org/cgit/linux/kernel/git/andrea/aa.git/commit/?h=userfault&id=d0df59f21f2cde4c49879c00586ce3cb1e3860fe

Great!

> I was also asked if we could return the full address of the fault
> including the page offset. In the end I also implemented this
> incremental to your change:
> 
> http://git.kernel.org/cgit/linux/kernel/git/andrea/aa.git/commit/?h=userfault&id=c308fc81b0a9c53c11b33331ad00d8e5b9763e60
> 
> Let me know if you're ok with it. 

Yup, this is very close to what I did in my set -- introduced a message to
report back to the user-space on read. But my message is more than 8+2*1 bytes,
so we'll have one message for 0xAA API and another one for 0xAB (new) one :)

> The commit header explains more why
> I think the bits below PAGE_SHIFT of the fault address aren't
> interesting but why I did this change anyway.
> 
> After reviewing this last change I think it's time to make a proper
> submit and it's polished enough for merging in -mm after proper review
> of the full patchset.

Yup, fully agree :) And I will soon send the re-based non-cooperative patchset
with new API version, longer messages, fork and remap events reporting.

-- Pavel

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