On 02/14/2019 10:52 AM, Vlastimil Babka wrote:
On 2/13/19 8:30 PM, Dave Hansen wrote:
  static __init int gigantic_pages_init(void)
        /* With compaction or CMA we can allocate gigantic pages at runtime */
diff --git a/fs/Kconfig b/fs/Kconfig
index ac474a61be37..8fecd3ea5563 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -207,8 +207,9 @@ config HUGETLB_PAGE
        def_bool TMPFS || HUGETLBFS
+       default y if (MEMORY_ISOLATION && MIGRATION) || CMA
This takes a hard dependency (#if) and turns it into a Kconfig *default*
that can be overridden.  That seems like trouble.

Shouldn't it be:

        def_bool y
        depends on (MEMORY_ISOLATION && MIGRATION) || CMA
Agreed. Also I noticed that it now depends on MIGRATION instead of
COMPACTION. That intention is correct IMHO, but will fail to
compile/link when both COMPACTION and CMA are disabled, and would need
more changes in mm/internal.h and mm/compaction.c (possibly just
replacing CMA in all "if defined CONFIG_COMPACTION || defined
CONFIG_CMA" instances with COMPACTION_CORE, but there might be more
problems, wanna try? :)

Let's be honest, that's a "typo" :) Migration is logical to me but
that's because I don't know much about compaction. Thanks for
noticing it.
I'll take a look at what you propose to do too.

Also, I realized that COMPACTION_CORE is a wrong name, sorry about that.
What the config really provides is alloc_contig_range(), so it should be
named either CONFIG_CMA_CORE (as it provides contiguous memory
allocation, but not the related reservation and accounting), or
something like CONFIG_CONTIG_ALLOC. I would also move it from fs/Kconfig
to mm/Kconfig.

No problem, I was not inspired either. I'll send a v3 with the renaming
you propose.


Thank you.


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