From: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: linux-nvdimm <linux-nvdimm@lists.01.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Jan Kara <jack@suse.cz>, Linux MM <linux-mm@kvack.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] mm/pmem: Avoid inserting hugepage PTE entry with fsdax if hugepage support is disabled
Date: Wed, 10 Feb 2021 06:18:11 +0100 [thread overview]
Message-ID: <CAM9Jb+gS22vbRrSLfTG=9VhJfrMOGvm4r8HB1nBMS4RK9W06FQ@mail.gmail.com> (raw)
In-Reply-To: <20210205023956.417587-1-aneesh.kumar@linux.ibm.com>
> Differentiate between hardware not supporting hugepages and user disabling THP
> via 'echo never > /sys/kernel/mm/transparent_hugepage/enabled'
>
> For the devdax namespace, the kernel handles the above via the
> supported_alignment attribute and failing to initialize the namespace
> if the namespace align value is not supported on the platform.
>
> For the fsdax namespace, the kernel will continue to initialize
> the namespace. This can result in the kernel creating a huge pte
> entry even though the hardware don't support the same.
>
> We do want hugepage support with pmem even if the end-user disabled THP
> via sysfs file (/sys/kernel/mm/transparent_hugepage/enabled). Hence
> differentiate between hardware/firmware lacking support vs user-controlled
> disable of THP and prevent a huge fault if the hardware lacks hugepage
> support.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
> include/linux/huge_mm.h | 15 +++++++++------
> mm/huge_memory.c | 6 +++++-
> 2 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 6a19f35f836b..ba973efcd369 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -78,6 +78,7 @@ static inline vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn,
> }
>
> enum transparent_hugepage_flag {
> + TRANSPARENT_HUGEPAGE_NEVER_DAX,
> TRANSPARENT_HUGEPAGE_FLAG,
> TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
> TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
> @@ -123,6 +124,13 @@ extern unsigned long transparent_hugepage_flags;
> */
> static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
> {
> +
> + /*
> + * If the hardware/firmware marked hugepage support disabled.
> + */
> + if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_NEVER_DAX))
> + return false;
> +
> if (vma->vm_flags & VM_NOHUGEPAGE)
> return false;
>
> @@ -134,12 +142,7 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
>
> if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG))
> return true;
> - /*
> - * For dax vmas, try to always use hugepage mappings. If the kernel does
> - * not support hugepages, fsdax mappings will fallback to PAGE_SIZE
> - * mappings, and device-dax namespaces, that try to guarantee a given
> - * mapping size, will fail to enable
> - */
> +
> if (vma_is_dax(vma))
> return true;
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 9237976abe72..d698b7e27447 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -386,7 +386,11 @@ static int __init hugepage_init(void)
> struct kobject *hugepage_kobj;
>
> if (!has_transparent_hugepage()) {
> - transparent_hugepage_flags = 0;
> + /*
> + * Hardware doesn't support hugepages, hence disable
> + * DAX PMD support.
> + */
> + transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX;
> return -EINVAL;
> }
Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
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prev parent reply other threads:[~2021-02-10 5:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-05 2:39 [PATCH] mm/pmem: Avoid inserting hugepage PTE entry with fsdax if hugepage support is disabled Aneesh Kumar K.V
2021-02-05 8:29 ` David Hildenbrand
2021-02-05 17:47 ` Dan Williams
2021-02-10 5:18 ` Pankaj Gupta [this message]
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