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

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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



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