Re: [PATCH v3 3/4] hugetlbfs: remove hugetlb_add_hstate() warning for existing hstate

From: Anders Roxell
Date: Mon Apr 20 2020 - 15:41:19 EST

On Fri, 17 Apr 2020 at 20:52, 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>
> Acked-by: Mina Almasry <almasrymina@xxxxxxxxxx>

When I build an arm64 kernel on today's next-20200420 and ran that in
qemu I got the following output [1]:

...
[ 311.326817][ T1] kobject: 'drivers' ((____ptrval____)):
kobject_add_internal: parent: 'coresight', set: '<NULL>'
[ 311.331513][ T1] kobject: 'drivers' ((____ptrval____)): kobject_uevent_env
[ 311.334514][ T1] kobject: 'drivers' ((____ptrval____)):
kobject_uevent_env: filter function caused the event to drop!
[ 311.340127][ T1] bus: 'coresight': registered
[ 311.342228][ T1] initcall coresight_init+0x0/0x64 returned 0
after 27343 usecs
[ 311.349740][ T1] calling debug_traps_init+0x0/0xa4 @ 1
[ 311.352138][ T1] initcall debug_traps_init+0x0/0xa4 returned 0
after 0 usecs
[ 311.355550][ T1] calling reserve_memblock_reserved_regions+0x0/0x374 @ 1
[ 311.364913][ T1] initcall
reserve_memblock_reserved_regions+0x0/0x374 returned 0 after 7812
usecs
[ 311.368937][ T1] calling aarch32_alloc_vdso_pages+0x0/0x1d0 @ 1
[ 311.371819][ T1] initcall aarch32_alloc_vdso_pages+0x0/0x1d0
returned 0 after 0 usecs
[ 311.375608][ T1] calling vdso_init+0x0/0x52c @ 1
[ 311.378092][ T1] initcall vdso_init+0x0/0x52c returned 0 after 0 usecs
[ 311.381386][ T1] calling arch_hw_breakpoint_init+0x0/0x178 @ 1
[ 311.384007][ T1] hw-breakpoint: found 6 breakpoint and 4
watchpoint registers.
[ 311.388120][ T1] initcall arch_hw_breakpoint_init+0x0/0x178
returned 0 after 3906 usecs
[ 311.391924][ T1] calling asids_update_limit+0x0/0x110 @ 1
[ 311.394390][ T1] ASID allocator initialised with 65536 entries
[ 311.397427][ T1] initcall asids_update_limit+0x0/0x110 returned
0 after 3906 usecs
[ 311.400749][ T1] calling hugetlbpage_init+0x0/0x7c @ 1
[ 311.403581][ T1] Unexpected kernel BRK exception at EL1
[ 311.405771][ T1] Internal error: ptrace BRK handler: f20003e8
[#1] PREEMPT SMP
[ 311.408759][ T1] Modules linked in:
[ 311.410514][ T1] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G
T 5.7.0-rc2-next-20200420-03722-ge4ba9b47e4ed #1
[ 311.415175][ T1] Hardware name: linux,dummy-virt (DT)
[ 311.417466][ T1] pstate: 80400005 (Nzcv daif +PAN -UAO)
[ 311.419887][ T1] pc : hugetlb_add_hstate+0x68/0x4f0
[ 311.422171][ T1] lr : hugetlb_add_hstate+0x68/0x4f0
[ 311.424354][ T1] sp : ffff000069c07c60
[ 311.426124][ T1] x29: ffff000069c07c60 x28: ffff00006a7f8058
[ 311.428754][ T1] x27: 0000000000000000 x26: ffffa00013f56950
[ 311.431376][ T1] x25: ffffa000141b8000 x24: ffff00006a7f8040
[ 311.433987][ T1] x23: 1fffe0000d380fae x22: 00000000fffffff8
[ 311.436574][ T1] x21: 0000000100000000 x20: ffffa000141b8000
[ 311.439167][ T1] x19: ec632d51be3d2507 x18: 0000000000001a68
[ 311.441763][ T1] x17: 00000000000013e0 x16: 0000000000001a94
[ 311.444386][ T1] x15: 0000000000001a68 x14: 6573752036303933
[ 311.447034][ T1] x13: 2072657466612030 x12: 00000000000025b0
[ 311.449639][ T1] x11: 00000000f1f1f1f1 x10: 0000000041b58ab3
[ 311.452238][ T1] x9 : ffffa000139a833c x8 : 1ffff40002bf2c23
[ 311.454849][ T1] x7 : ffff940002bf2c23 x6 : ffffa00015f9611b
[ 311.457480][ T1] x5 : ffff00006a7f8040 x4 : 0000000000000000
[ 311.460124][ T1] x3 : ffffa000139fd98c x2 : 00000000fffffff8
[ 311.462737][ T1] x1 : ffff00006a7f8040 x0 : 0000000000000000
[ 311.465322][ T1] Call trace:
[ 311.466818][ T1] hugetlb_add_hstate+0x68/0x4f0
[ 311.468934][ T1] hugetlbpage_init+0x34/0x7c
[ 311.470934][ T1] do_one_initcall+0x480/0xa40
[ 311.472996][ T1] kernel_init_freeable+0x7a0/0x968
[ 311.475224][ T1] kernel_init+0x20/0x1f8
[ 311.477078][ T1] ret_from_fork+0x10/0x18
[ 311.479053][ T1] Code: 972762be 7100fedf 54000069 97276197 (d4207d00)
[ 311.482106][ T1] _warn_unseeded_randomness: 18 callbacks suppressed
[ 311.482255][ T1] random: get_random_bytes called from
print_oops_end_marker+0x48/0x80 with crng_init=0
[ 311.482321][ T1] ---[ end trace 60df362baad50718 ]---
[ 311.491423][ T1] Kernel panic - not syncing: Fatal exception
[ 311.494038][ T1] ---[ end Kernel panic - not syncing: Fatal exception ]---

If I revert this patch I can't see the problem anymore...

Any idea what happens?

This is the kernel.config [1] I'm using, its from an allmodconfig kernel build

Cheers,
Anders
[1] https://people.linaro.org/~anders.roxell/output-next-20200420.log
[2] https://builds.tuxbuild.com/U7ufblLydTsSvle27GSPAA/kernel.config


> ---
> 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 | 9 ++++++---
> 6 files changed, 17 insertions(+), 34 deletions(-)
>
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index f706b821aba6..21fa98b51e00 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(PUD_SHIFT - 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(CONT_PMD_SHIFT - PAGE_SHIFT);
> + hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
> + hugetlb_add_hstate(CONT_PTE_SHIFT - PAGE_SHIFT);
>
> return 0;
> }
> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index 2c3fa0a7787b..4d5ed1093615 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((unsigned long)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 4e5d7e9f0eef..932dadfdca54 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 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 4618f96fd30f..ae819a16d07a 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 937d640a89e3..cf5781142716 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 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 b2d276408cec..0e6eb755ae94 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3222,8 +3222,7 @@ 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) {
> @@ -3268,7 +3267,6 @@ 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);
> @@ -3343,6 +3341,11 @@ static int __init hugepagesz_setup(char *s)
> return 0;
> }
>
> + if (size_to_hstate(size)) {
> + pr_warn("HugeTLB: hugepagesz %s specified twice, ignoring\n", s);
> + return 0;
> + }
> +
> hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
> return 1;
> }
> --
> 2.25.2
>