Re: [patch 3/6] mempolicy: add MPOL_F_STATIC_NODES flag

From: David Rientjes
Date: Tue Feb 26 2008 - 16:03:23 EST


On Tue, 26 Feb 2008, Paul Jackson wrote:

> > return do_mbind(start, len, mode, mode_flags, &nodes, flags);
>
> The intermingling of 'flags', 'mode' and 'mode_flags' to refer to the
> low bits, the high bits or all the bits of the flags field is handled
> fairly carefully in your patch, but can still be a bit difficult to
> keep track of which is which when reading.
>
> I'll wager not many readers can immediately say what the 'mode',
> 'mode_flags' and 'flags' refer to, in the above code snippet, for
> example.
>
> Do you have any suggestions on how to further improve the clarity of
> this code?
>

This is a natural implementation detail to accomodate your insistance that
the mode and flags be passed as separate actuals throughout many of the
mm/mempolicy.c functions.

No reader is going to understand immediately what 'mode', 'mode_flags',
and 'flags' are if you only provide a single line of the code like that.

It becomes rather obvious what they represent when you read the entire
sys_mbind() implementation, which is serving a syscall that provides its
own formal for passing flags. The name 'mode_flags' is exactly what it
is: flags for the mempolicy mode.

David
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