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

From: Mina Almasry <almasrymina@google.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Linux-MM <linux-mm@kvack.org>,
	open list <linux-kernel@vger.kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
	linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
	linux-doc@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	"David S . Miller" <davem@davemloft.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Jonathan Corbet <corbet@lwn.net>, Longpeng <longpeng2@huawei.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 3/4] hugetlbfs: remove hugetlb_add_hstate() warning for existing hstate
Date: Mon, 23 Mar 2020 17:01:03 -0700	[thread overview]
Message-ID: <CAHS8izN1Q+yiZq8zcU8hoojafcQ19W7XQx-HyFm3Ud8hSvN1Nw@mail.gmail.com> (raw)
In-Reply-To: <20200318220634.32100-4-mike.kravetz@oracle.com>

On Wed, Mar 18, 2020 at 3:07 PM Mike Kravetz <mike.kravetz@oracle.com> 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@oracle.com>
> ---
>  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? Does
that mean the warning prints if you specify this size? Maybe then
clarify the message like:

'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
>
>