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Date:   Wed, 8 Apr 2020 17:36:02 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Christoph Hellwig <hch@lst.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
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        Sakari Ailus <sakari.ailus@linux.intel.com>,
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Subject: Re: [PATCH 10/28] mm: only allow page table mappings for built-in
 zsmalloc
Message-ID: <20200408153602.GA28081@lst.de>
References: <20200408115926.1467567-1-hch@lst.de> <20200408115926.1467567-11-hch@lst.de> <c0c86feb-b3d8-78f2-127f-71d682ffc51f@infradead.org> <20200408151203.GN20730@hirez.programming.kicks-ass.net> <20200408151519.GQ21484@bombadil.infradead.org>
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On Wed, Apr 08, 2020 at 08:15:19AM -0700, Matthew Wilcox wrote:
> > > >  config ZSMALLOC_PGTABLE_MAPPING
> > > >  	bool "Use page table mapping to access object in zsmalloc"
> > > > -	depends on ZSMALLOC
> > > > +	depends on ZSMALLOC=y
> > > 
> > > It's a bool so this shouldn't matter... not needed.
> > 
> > My mm/Kconfig has:
> > 
> > config ZSMALLOC
> > 	tristate "Memory allocator for compressed pages"
> > 	depends on MMU
> > 
> > which I think means it can be modular, no?
> 
> Randy means that ZSMALLOC_PGTABLE_MAPPING is a bool, so I think hch's patch
> is wrong ... if ZSMALLOC is 'm' then ZSMALLOC_PGTABLE_MAPPING would become
> 'n' instead of 'y'.

In Linus' tree you can select PGTABLE_MAPPING=y with ZSMALLOC=m,
and that fits my understanding of the kbuild language.  With this
patch I can't anymore.