svn commit: r289565 - head/sys/ofed/include/linux

[Hans Petter Selasky]

On 10/19/15 17:01, Konstantin Belousov wrote:
> On Mon, Oct 19, 2015 at 10:56:32AM +0000, Hans Petter Selasky wrote:
>> Author: hselasky
>> Date: Mon Oct 19 10:56:32 2015
>> New Revision: 289565
>> URL: https://svnweb.freebsd.org/changeset/base/289565
>>
>> Log:
>>    Merge LinuxKPI changes from DragonflyBSD:
>>    - Implement pagefault_disable() and pagefault_enable().
>>
>>    Sponsored by:	Mellanox Technologies
>>
>> Modified:
>>    head/sys/ofed/include/linux/uaccess.h
>>
>> Modified: head/sys/ofed/include/linux/uaccess.h
>> ==============================================================================
>> --- head/sys/ofed/include/linux/uaccess.h	Mon Oct 19 10:54:24 2015	(r289564)
>> +++ head/sys/ofed/include/linux/uaccess.h	Mon Oct 19 10:56:32 2015	(r289565)
>> @@ -2,7 +2,8 @@
>>    * Copyright (c) 2010 Isilon Systems, Inc.
>>    * Copyright (c) 2010 iX Systems, Inc.
>>    * Copyright (c) 2010 Panasas, Inc.
>> - * Copyright (c) 2013, 2014 Mellanox Technologies, Ltd.
>> + * Copyright (c) 2013-2015 Mellanox Technologies, Ltd.
>> + * Copyright (c) 2015 Fran??ois Tigeot
>>    * All rights reserved.
>>    *
>>    * Redistribution and use in source and binary forms, with or without
>> @@ -32,4 +33,14 @@
>>   #define	get_user(_x, _p)	-copyin((_p), &(_x), sizeof(*(_p)))
>>   #define	put_user(_x, _p)	-copyout(&(_x), (_p), sizeof(*(_p)))
>>
>> +static inline void pagefault_disable(void)
>> +{
>> +	curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR);
>> +}
>> +
>> +static inline void pagefault_enable(void)
>> +{
>> +	curthread_pflags_restore(~(TDP_NOFAULTING | TDP_RESETSPUR));
>> +}
>> +
>>   #endif	/* _LINUX_UACCESS_H_ */
>
> This is wrong on many counts.  First, we already provide the wrappers to
> implement the nofaulting behaviour, see vm_fault_disable_pagefaults()
> and vm_fault_enable_pagefaults().
>
> Second, your implementation ignores possible recursion on the
> state, unconditionally re-enabling faulting, and more seriously, it
> unconditionally obliterates the spurious faults tracker.
>
> The return value from vm_fault_disable_pagefaults() is there for the reason,
> and if Linux KPI does not have a place to store the state, some replacement
> must be implemented instead of silently corrupting the flags on enable.
>

Hi Konstantin,

Thank you for you input. I'll update these functions according to your 
suggestion. We can have a return value, even if Linux doesn't. It 
doesn't have to be exactly the same and then I can set a compiler 
attribute that the return value must be checked.

--HPS