Re: [PATCH 3/6] mm: CONFIG_MMU for PG_mlocked

[Hugh Dickins <hugh.dickins@tiscali.co.uk>]

On Wed, 11 Nov 2009, KOSAKI Motohiro wrote:
> > Remove three degrees of obfuscation, left over from when we had
> > CONFIG_UNEVICTABLE_LRU.  MLOCK_PAGES is CONFIG_HAVE_MLOCKED_PAGE_BIT
> > is CONFIG_HAVE_MLOCK is CONFIG_MMU.  rmap.o (and memory-failure.o)
> > are only built when CONFIG_MMU, so don't need such conditions at all.
> 
> I don't recall why Lee added this config option. but it seems very
> reasonable and I storongly like it.
> 
> At least, vmscan folks never said "please try to disable CONFIG_MLOCK".
> It mean this option didn't help our debug.
> 
> 	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Thanks.  CONFIG_HAVE_MLOCKED_PAGE_BIT and CONFIG_HAVE_MLOCK were both
just internal, automatically defaulted options which the user never
saw (except in .config).  I think they were there to sort out the
interdependencies between CONFIG_MMU and CONFIG_UNEVICTABLE_LRU,
and probably other historical issues while people decided whether
or not to go ahead with having a page bit for the thing.  So no
user should notice their disappearance: removing them just makes
the code clearer, that's all.

Hugh

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