linux-kernel - Re: [PATCH] mm/hugetlb: remove gigantic page support for HIGHMEM

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Message-ID: <20180711205702.d4xeu552xgxjbse3@linux-r8p5>
Date:   Wed, 11 Jul 2018 13:57:02 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michal Hocko <mhocko@...nel.org>,
        Cannon Matthews <cannonmatthews@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm/hugetlb: remove gigantic page support for HIGHMEM

On Wed, 11 Jul 2018, Mike Kravetz wrote:

>This reverts commit ee8f248d266e ("hugetlb: add phys addr to struct
>huge_bootmem_page")
>
>At one time powerpc used this field and supporting code. However that
>was removed with commit 79cc38ded1e1 ("powerpc/mm/hugetlb: Add support
>for reserving gigantic huge pages via kernel command line").
>
>There are no users of this field and supporting code, so remove it.

Considering the title, don't you wanna also get rid of try_to_free_low()
and something like the following, which I'm sure can be done fancier, and
perhaps also thp?

diff --git a/fs/Kconfig b/fs/Kconfig
index ac474a61be37..849da70e35d6 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -192,8 +192,8 @@ config TMPFS_XATTR
 
 config HUGETLBFS
        bool "HugeTLB file system support"
-       depends on X86 || IA64 || SPARC64 || (S390 && 64BIT) || \
-                  SYS_SUPPORTS_HUGETLBFS || BROKEN
+       depends on !HIGHMEM && (X86 || IA64 || SPARC64 || (S390 && 64BIT) || \
+                  SYS_SUPPORTS_HUGETLBFS || BROKEN)
        help
          hugetlbfs is a filesystem backing for HugeTLB pages, based on
          ramfs. For architectures that support it, say Y here and read

Thanks,
Davidlohr