mm/hugetlb: remove gigantic page support for HIGHMEM

Commit Message

Davidlohr Bueso July 11, 2018, 8:57 p.m. UTC

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?


Thanks,
Davidlohr

Comments

Mike Kravetz July 11, 2018, 9:36 p.m. UTC | #1

On 07/11/2018 01:57 PM, Davidlohr Bueso wrote:
> 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?

Not really.  The intention is to only remove gigantic huge page support for
HIGHMEN systems.  Non-gigantic huge pages on HIGHMEN systems should still
work/be supported.  So, we do not want to make the config change or get
rid of try_to_free_low().

Actually, I simply wanted to revert the specific patch which enabled gigantic
huge pages on HIGHMEM systems.  I did see that check in try_to_free_low(),

	if (hstate_is_gigantic(h))
		return;

and considered for a minute turning that into a VM_BUG or WARN, but decided
to leave it as is.

Do you think the title should be changed to simply 'revert commit
ee8f248d266e'?

Patch

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