Date:   Fri, 24 Feb 2023 14:35:01 -0800
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     James Houghton <jthoughton@google.com>
Cc:     Muchun Song <songmuchun@bytedance.com>,
        Peter Xu <peterx@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Mina Almasry <almasrymina@google.com>,
        Zach O'Keefe <zokeefe@google.com>,
        Manish Mishra <manish.mishra@nutanix.com>,
        Naoya Horiguchi <naoya.horiguchi@nec.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Yang Shi <shy828301@gmail.com>,
        Frank van der Linden <fvdl@google.com>,
        Jiaqi Yan <jiaqiyan@google.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 07/46] mm: add VM_HUGETLB_HGM VMA flag
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References: <20230218002819.1486479-1-jthoughton@google.com>
 <20230218002819.1486479-8-jthoughton@google.com>
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On 02/18/23 00:27, James Houghton wrote:
> VM_HUGETLB_HGM indicates that a HugeTLB VMA may contain high-granularity
> mappings. Its VmFlags string is "hm".
> 
> Signed-off-by: James Houghton <jthoughton@google.com>
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 6a96e1713fd5..77b72f42556a 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c

Acked-by: Mike Kravetz <mike.kravetz@oracle.com>

If there is any push back on using a bit in vm flags, we can go back to
your original scheme of embedding info in the hugetlb per-vma structure.
-- 
Mike Kravetz

> @@ -711,6 +711,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
>  #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
>  		[ilog2(VM_UFFD_MINOR)]	= "ui",
>  #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +		[ilog2(VM_HUGETLB_HGM)]	= "hm",
> +#endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
>  	};
>  	size_t i;
>  
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 2992a2d55aee..9d3216b4284a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -383,6 +383,13 @@ extern unsigned int kobjsize(const void *objp);
>  # define VM_UFFD_MINOR		VM_NONE
>  #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
>  
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +# define VM_HUGETLB_HGM_BIT	38
> +# define VM_HUGETLB_HGM		BIT(VM_HUGETLB_HGM_BIT)	/* HugeTLB high-granularity mapping */
> +#else /* !CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
> +# define VM_HUGETLB_HGM		VM_NONE
> +#endif /* CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING */
> +
>  /* Bits set in the VMA until the stack is in its final location */
>  #define VM_STACK_INCOMPLETE_SETUP	(VM_RAND_READ | VM_SEQ_READ)
>  
> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index 9db52bc4ce19..bceb960dbada 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -162,6 +162,12 @@ IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")
>  # define IF_HAVE_UFFD_MINOR(flag, name)
>  #endif
>  
> +#ifdef CONFIG_HUGETLB_HIGH_GRANULARITY_MAPPING
> +# define IF_HAVE_HUGETLB_HGM(flag, name) {flag, name},
> +#else
> +# define IF_HAVE_HUGETLB_HGM(flag, name)
> +#endif
> +
>  #define __def_vmaflag_names						\
>  	{VM_READ,			"read"		},		\
>  	{VM_WRITE,			"write"		},		\
> @@ -186,6 +192,7 @@ IF_HAVE_UFFD_MINOR(VM_UFFD_MINOR,	"uffd_minor"	)		\
>  	{VM_ACCOUNT,			"account"	},		\
>  	{VM_NORESERVE,			"noreserve"	},		\
>  	{VM_HUGETLB,			"hugetlb"	},		\
> +IF_HAVE_HUGETLB_HGM(VM_HUGETLB_HGM,	"hugetlb_hgm"	)		\
>  	{VM_SYNC,			"sync"		},		\
>  	__VM_ARCH_SPECIFIC_1				,		\
>  	{VM_WIPEONFORK,			"wipeonfork"	},		\
> -- 
> 2.39.2.637.g21b0678d19-goog
>