Re: [PATCH 3/4] hugetlbfs: remove hugetlb_add_hstate() warning for existing hstate

From: Mike Kravetz
Date: Mon Mar 23 2020 - 20:18:14 EST

On 3/23/20 5:01 PM, Mina Almasry wrote:
> On Wed, Mar 18, 2020 at 3:07 PM Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
>>
>> The routine hugetlb_add_hstate prints a warning if the hstate already
>> exists. This was originally done as part of kernel command line
>> parsing. If 'hugepagesz=' was specified more than once, the warning
>> pr_warn("hugepagesz= specified twice, ignoring\n");
>> would be printed.
>>
>> Some architectures want to enable all huge page sizes. They would
>> call hugetlb_add_hstate for all supported sizes. However, this was
>> done after command line processing and as a result hstates could have
>> already been created for some sizes. To make sure no warning were
>> printed, there would often be code like:
>> if (!size_to_hstate(size)
>> hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT)
>>
>> The only time we want to print the warning is as the result of command
>> line processing. So, remove the warning from hugetlb_add_hstate and
>> add it to the single arch independent routine processing "hugepagesz=".
>> After this, calls to size_to_hstate() in arch specific code can be
>> removed and hugetlb_add_hstate can be called without worrying about
>> warning messages.
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>> ---
>> arch/arm64/mm/hugetlbpage.c | 16 ++++------------
>> arch/powerpc/mm/hugetlbpage.c | 3 +--
>> arch/riscv/mm/hugetlbpage.c | 2 +-
>> arch/sparc/mm/init_64.c | 19 ++++---------------
>> arch/x86/mm/hugetlbpage.c | 2 +-
>> mm/hugetlb.c | 10 +++++++---
>> 6 files changed, 18 insertions(+), 34 deletions(-)
>>
>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>> index 4aa9534a45d7..050809e6f0a9 100644
>> --- a/arch/arm64/mm/hugetlbpage.c
>> +++ b/arch/arm64/mm/hugetlbpage.c
>> @@ -441,22 +441,14 @@ void huge_ptep_clear_flush(struct vm_area_struct *vma,
>> clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
>> }
>>
>> -static void __init add_huge_page_size(unsigned long size)
>> -{
>> - if (size_to_hstate(size))
>> - return;
>> -
>> - hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
>> -}
>> -
>> static int __init hugetlbpage_init(void)
>> {
>> #ifdef CONFIG_ARM64_4K_PAGES
>> - add_huge_page_size(PUD_SIZE);
>> + hugetlb_add_hstate(ilog2(PUD_SIZE) - PAGE_SHIFT);
>> #endif
>> - add_huge_page_size(CONT_PMD_SIZE);
>> - add_huge_page_size(PMD_SIZE);
>> - add_huge_page_size(CONT_PTE_SIZE);
>> + hugetlb_add_hstate(ilog2(CONT_PMD_SIZE) - PAGE_SHIFT);
>> + hugetlb_add_hstate(ilog2(PMD_SIZE) - PAGE_SHIFT);
>> + hugetlb_add_hstate(ilog2(CONT_PTE_SIZE) - PAGE_SHIFT);
>>
>> return 0;
>> }
>> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
>> index 166960ba1236..f46464ba6fb4 100644
>> --- a/arch/powerpc/mm/hugetlbpage.c
>> +++ b/arch/powerpc/mm/hugetlbpage.c
>> @@ -584,8 +584,7 @@ static int __init add_huge_page_size(unsigned long long size)
>> if (!arch_hugetlb_valid_size(size))
>> return -EINVAL;
>>
>> - if (!size_to_hstate(size))
>> - hugetlb_add_hstate(shift - PAGE_SHIFT);
>> + hugetlb_add_hstate(shift - PAGE_SHIFT);
>> return 0;
>> }
>>
>> diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
>> index bdf89d7eb714..beaa91941db8 100644
>> --- a/arch/riscv/mm/hugetlbpage.c
>> +++ b/arch/riscv/mm/hugetlbpage.c
>> @@ -26,7 +26,7 @@ bool __init arch_hugetlb_valid_size(unsigned long long size)
>> static __init int gigantic_pages_init(void)
>> {
>> /* With CONTIG_ALLOC, we can allocate gigantic pages at runtime */
>> - if (IS_ENABLED(CONFIG_64BIT) && !size_to_hstate(1UL << PUD_SHIFT))
>> + if (IS_ENABLED(CONFIG_64BIT))
>> hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
>> return 0;
>> }
>> diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
>> index 5c29203fd460..8f619edc8f8c 100644
>> --- a/arch/sparc/mm/init_64.c
>> +++ b/arch/sparc/mm/init_64.c
>> @@ -325,23 +325,12 @@ static void __update_mmu_tsb_insert(struct mm_struct *mm, unsigned long tsb_inde
>> }
>>
>> #ifdef CONFIG_HUGETLB_PAGE
>> -static void __init add_huge_page_size(unsigned long size)
>> -{
>> - unsigned int order;
>> -
>> - if (size_to_hstate(size))
>> - return;
>> -
>> - order = ilog2(size) - PAGE_SHIFT;
>> - hugetlb_add_hstate(order);
>> -}
>> -
>> static int __init hugetlbpage_init(void)
>> {
>> - add_huge_page_size(1UL << HPAGE_64K_SHIFT);
>> - add_huge_page_size(1UL << HPAGE_SHIFT);
>> - add_huge_page_size(1UL << HPAGE_256MB_SHIFT);
>> - add_huge_page_size(1UL << HPAGE_2GB_SHIFT);
>> + hugetlb_add_hstate(HPAGE_64K_SHIFT - PAGE_SHIFT);
>> + hugetlb_add_hstate(HPAGE_SHIFT - PAGE_SHIFT);
>> + hugetlb_add_hstate(HPAGE_256MB_SHIFT - PAGE_SHIFT);
>> + hugetlb_add_hstate(HPAGE_2GB_SHIFT - PAGE_SHIFT);
>>
>> return 0;
>> }
>> diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
>> index dd3ed09f6c23..8a3f586e1217 100644
>> --- a/arch/x86/mm/hugetlbpage.c
>> +++ b/arch/x86/mm/hugetlbpage.c
>> @@ -195,7 +195,7 @@ bool __init arch_hugetlb_valid_size(unsigned long long size)
>> static __init int gigantic_pages_init(void)
>> {
>> /* With compaction or CMA we can allocate gigantic pages at runtime */
>> - if (boot_cpu_has(X86_FEATURE_GBPAGES) && !size_to_hstate(1UL << PUD_SHIFT))
>> + if (boot_cpu_has(X86_FEATURE_GBPAGES))
>> hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
>> return 0;
>> }
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index cd4ec07080fb..cc85b4f156ca 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -3116,8 +3116,7 @@ static int __init hugetlb_init(void)
>> }
>>
>> default_hstate_size = HPAGE_SIZE;
>> - if (!size_to_hstate(default_hstate_size))
>> - hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
>> + hugetlb_add_hstate(HUGETLB_PAGE_ORDER);
>> }
>> default_hstate_idx = hstate_index(size_to_hstate(default_hstate_size));
>> if (default_hstate_max_huge_pages) {
>> @@ -3155,7 +3154,6 @@ void __init hugetlb_add_hstate(unsigned int order)
>> unsigned long i;
>>
>> if (size_to_hstate(PAGE_SIZE << order)) {
>> - pr_warn("hugepagesz= specified twice, ignoring\n");
>> return;
>> }
>> BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);
>> @@ -3231,6 +3229,12 @@ static int __init hugepagesz_setup(char *s)
>> return 0;
>> }
>>
>> + if (size_to_hstate(size)) {
>> + pr_warn("HugeTLB: hugepagesz %s specified twice, ignoring\n",
>> + saved_s);
>> + return 0;
>> + }
>> +
>
> Not too familiar with the code but I'm a bit confused by this print.
> AFAICT this prints the warning when hugepagesz= refers to a hugepage
> that is already added via hugetlb_add_hstate, but there is a default
> hstate added here without the user specifying hugepagesz, no?

Correct.

> Does
> that mean the warning prints if you specify this size?

The code which adds the default hstate (in hugetlb_init) runs after this
code which is reading/processing command line options. So, the case you
are concerned with will not happen.

Thanks for taking a look,
--
Mike Kravetz

> 'HugeTLB: hugepage size already supported: xxxxx' or
> 'HugeTLB: hugepage size xxxx specified twice or is default size, ignoring.'
>
> Or don't print anything if it's the default size.
>
>> hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
>> return 1;
>> }
>> --
>> 2.24.1