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Message-ID: <0164d185-12db-478a-93fd-b07d5fe00599@arm.com>
Date: Wed, 15 Nov 2023 14:40:11 +0000
From: Steven Price <steven.price@....com>
To: Barry Song <21cnbao@...il.com>, akpm@...ux-foundation.org,
ryan.roberts@....com, catalin.marinas@....com, will@...nel.org
Cc: david@...hat.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
mhocko@...e.com, shy828301@...il.com, v-songbaohua@...o.com,
wangkefeng.wang@...wei.com, willy@...radead.org, xiang@...nel.org,
ying.huang@...el.com, yuzhao@...gle.com
Subject: Re: [RFC V3 PATCH] arm64: mm: swap: save and restore mte tags for
large folios
On 14/11/2023 01:43, Barry Song wrote:
> This patch makes MTE tags saving and restoring support large folios,
> then we don't need to split them into base pages for swapping out
> on ARM64 SoCs with MTE.
>
> arch_prepare_to_swap() should take folio rather than page as parameter
> because we support THP swap-out as a whole.
>
> Meanwhile, arch_swap_restore() should use page parameter rather than
> folio as swap-in always works at the granularity of base pages right
> now.
>
> arch_thp_swp_supported() is dropped since ARM64 MTE was the only one
> who needed it.
>
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
LGTM!
Reviewed: Steven Price <steven.price@....com>
Although one NIT below you might want to fix.
> ---
> rfc v3:
> * move arch_swap_restore() to take page rather than folio according to
> the discussion with Ryan and Steven;
> * fix some other issues commented by Ryan
>
> rfc v2:
> https://lore.kernel.org/lkml/20231104093423.170054-1-v-songbaohua@oppo.com/
> rfc v1:
> https://lore.kernel.org/lkml/20231102223643.7733-1-v-songbaohua@oppo.com/
>
> arch/arm64/include/asm/pgtable.h | 21 ++++----------------
> arch/arm64/mm/mteswap.c | 34 ++++++++++++++++++++++++++++++++
> include/linux/huge_mm.h | 12 -----------
> include/linux/pgtable.h | 4 ++--
> mm/memory.c | 2 +-
> mm/page_io.c | 2 +-
> mm/shmem.c | 2 +-
> mm/swap_slots.c | 2 +-
> mm/swapfile.c | 2 +-
> 9 files changed, 45 insertions(+), 36 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index b19a8aee684c..c3eef11c1a9e 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -45,12 +45,6 @@
> __flush_tlb_range(vma, addr, end, PUD_SIZE, false, 1)
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> -static inline bool arch_thp_swp_supported(void)
> -{
> - return !system_supports_mte();
> -}
> -#define arch_thp_swp_supported arch_thp_swp_supported
> -
> /*
> * Outside of a few very special situations (e.g. hibernation), we always
> * use broadcast TLB invalidation instructions, therefore a spurious page
> @@ -1036,12 +1030,8 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
> #ifdef CONFIG_ARM64_MTE
>
> #define __HAVE_ARCH_PREPARE_TO_SWAP
> -static inline int arch_prepare_to_swap(struct page *page)
> -{
> - if (system_supports_mte())
> - return mte_save_tags(page);
> - return 0;
> -}
> +#define arch_prepare_to_swap arch_prepare_to_swap
> +extern int arch_prepare_to_swap(struct folio *folio);
>
> #define __HAVE_ARCH_SWAP_INVALIDATE
> static inline void arch_swap_invalidate_page(int type, pgoff_t offset)
> @@ -1057,11 +1047,8 @@ static inline void arch_swap_invalidate_area(int type)
> }
>
> #define __HAVE_ARCH_SWAP_RESTORE
> -static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
> -{
> - if (system_supports_mte())
> - mte_restore_tags(entry, &folio->page);
> -}
> +#define arch_swap_restore arch_swap_restore
> +extern void arch_swap_restore(swp_entry_t entry, struct page *page);
>
> #endif /* CONFIG_ARM64_MTE */
>
> diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c
> index a31833e3ddc5..75c2836e8240 100644
> --- a/arch/arm64/mm/mteswap.c
> +++ b/arch/arm64/mm/mteswap.c
> @@ -68,6 +68,12 @@ void mte_invalidate_tags(int type, pgoff_t offset)
> mte_free_tag_storage(tags);
> }
>
> +static inline void __mte_invalidate_tags(struct page *page)
> +{
> + swp_entry_t entry = page_swap_entry(page);
> + mte_invalidate_tags(swp_type(entry), swp_offset(entry));
NIT: checkpatch will complain there should be blank line between these
two lines (declarations are followed by a blank line).
Steve
> +}
> +
> void mte_invalidate_tags_area(int type)
> {
> swp_entry_t entry = swp_entry(type, 0);
> @@ -83,3 +89,31 @@ void mte_invalidate_tags_area(int type)
> }
> xa_unlock(&mte_pages);
> }
> +
> +int arch_prepare_to_swap(struct folio *folio)
> +{
> + int err;
> + long i;
> +
> + if (system_supports_mte()) {
> + long nr = folio_nr_pages(folio);
> +
> + for (i = 0; i < nr; i++) {
> + err = mte_save_tags(folio_page(folio, i));
> + if (err)
> + goto out;
> + }
> + }
> + return 0;
> +
> +out:
> + while (i--)
> + __mte_invalidate_tags(folio_page(folio, i));
> + return err;
> +}
> +
> +void arch_swap_restore(swp_entry_t entry, struct page *page)
> +{
> + if (system_supports_mte())
> + mte_restore_tags(entry, page);
> +}
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index fa0350b0812a..f83fb8d5241e 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -400,16 +400,4 @@ static inline int split_folio(struct folio *folio)
> return split_folio_to_list(folio, NULL);
> }
>
> -/*
> - * archs that select ARCH_WANTS_THP_SWAP but don't support THP_SWP due to
> - * limitations in the implementation like arm64 MTE can override this to
> - * false
> - */
> -#ifndef arch_thp_swp_supported
> -static inline bool arch_thp_swp_supported(void)
> -{
> - return true;
> -}
> -#endif
> -
> #endif /* _LINUX_HUGE_MM_H */
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index af7639c3b0a3..87e3140a55ca 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -897,7 +897,7 @@ static inline int arch_unmap_one(struct mm_struct *mm,
> * prototypes must be defined in the arch-specific asm/pgtable.h file.
> */
> #ifndef __HAVE_ARCH_PREPARE_TO_SWAP
> -static inline int arch_prepare_to_swap(struct page *page)
> +static inline int arch_prepare_to_swap(struct folio *folio)
> {
> return 0;
> }
> @@ -914,7 +914,7 @@ static inline void arch_swap_invalidate_area(int type)
> #endif
>
> #ifndef __HAVE_ARCH_SWAP_RESTORE
> -static inline void arch_swap_restore(swp_entry_t entry, struct folio *folio)
> +static inline void arch_swap_restore(swp_entry_t entry, struct page *page)
> {
> }
> #endif
> diff --git a/mm/memory.c b/mm/memory.c
> index 1f18ed4a5497..fad238dd38e7 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4022,7 +4022,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> * when reading from swap. This metadata may be indexed by swap entry
> * so this must be called before swap_free().
> */
> - arch_swap_restore(entry, folio);
> + arch_swap_restore(entry, page);
>
> /*
> * Remove the swap entry and conditionally try to free up the swapcache.
> diff --git a/mm/page_io.c b/mm/page_io.c
> index cb559ae324c6..0fd832474c1d 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -189,7 +189,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
> * Arch code may have to preserve more data than just the page
> * contents, e.g. memory tags.
> */
> - ret = arch_prepare_to_swap(&folio->page);
> + ret = arch_prepare_to_swap(folio);
> if (ret) {
> folio_mark_dirty(folio);
> folio_unlock(folio);
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 91e2620148b2..7d32e50da121 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1892,7 +1892,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
> * Some architectures may have to restore extra metadata to the
> * folio after reading from swap.
> */
> - arch_swap_restore(swap, folio);
> + arch_swap_restore(swap, &folio->page);
>
> if (shmem_should_replace_folio(folio, gfp)) {
> error = shmem_replace_folio(&folio, gfp, info, index);
> diff --git a/mm/swap_slots.c b/mm/swap_slots.c
> index 0bec1f705f8e..2325adbb1f19 100644
> --- a/mm/swap_slots.c
> +++ b/mm/swap_slots.c
> @@ -307,7 +307,7 @@ swp_entry_t folio_alloc_swap(struct folio *folio)
> entry.val = 0;
>
> if (folio_test_large(folio)) {
> - if (IS_ENABLED(CONFIG_THP_SWAP) && arch_thp_swp_supported())
> + if (IS_ENABLED(CONFIG_THP_SWAP))
> get_swap_pages(1, &entry, folio_nr_pages(folio));
> goto out;
> }
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 4bc70f459164..6450e0279e35 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1784,7 +1784,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
> * when reading from swap. This metadata may be indexed by swap entry
> * so this must be called before swap_free().
> */
> - arch_swap_restore(entry, page_folio(page));
> + arch_swap_restore(entry, page);
>
> /* See do_swap_page() */
> BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
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