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charset=us-ascii Content-Disposition: inline In-Reply-To: <599769c3-0aef-4c5b-ac98-f109649862f7@arm.com> X-Rspamd-Queue-Id: 5F316140002 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: omsgtc8chmbnbmg1f71g8x7ugz937ygb X-HE-Tag: 1706809134-573496 X-HE-Meta: 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 quRh6aqW mjlzR2tqpE0Y93V/CrhNPMPa7qaF87e2kzTC7rlA1Jy6fezfbWzwB/xTJrVASzukn5lqN9FUqxbMZhgbu874/5mgFjPAjaQqLpoj5wpqDE4xmqnZphKO0sTcYwJYboYaHkLUOHuUR/bDylC7wPzvE+bR3qS2uMoZI3IUX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Feb 01, 2024 at 01:42:08PM +0530, Anshuman Khandual wrote: > > > On 1/25/24 22:12, Alexandru Elisei wrote: > > copy_user_highpage() will do memory allocation if there are saved tags for > > the destination page, and the page is missing tag storage. > > > > After commit a349d72fd9ef ("mm/pgtable: add rcu_read_lock() and > > rcu_read_unlock()s"), collapse_huge_page() calls > > __collapse_huge_page_copy() -> .. -> copy_user_highpage() with the RCU lock > > held, which means that copy_user_highpage() can only allocate memory using > > GFP_ATOMIC or equivalent. > > > > Get around this by refusing to collapse pages into a transparent huge page > > if the VMA is MTE-enabled. > > Makes sense when copy_user_highpage() will allocate memory for tag storage. > > > > > Signed-off-by: Alexandru Elisei > > --- > > > > Changes since rfc v2: > > > > * New patch. I think an agreement on whether copy*_user_highpage() should be > > always allowed to sleep, or should not be allowed, would be useful. > > This is a good question ! Even after preventing the collapse of MTE VMA here, > there still might be more paths where a sleeping (i.e memory allocating) > copy*_user_highpage() becomes problematic ? Exactly! > > > > > arch/arm64/include/asm/pgtable.h | 3 +++ > > arch/arm64/kernel/mte_tag_storage.c | 5 +++++ > > include/linux/khugepaged.h | 5 +++++ > > mm/khugepaged.c | 4 ++++ > > 4 files changed, 17 insertions(+) > > > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > > index 87ae59436162..d0473538c926 100644 > > --- a/arch/arm64/include/asm/pgtable.h > > +++ b/arch/arm64/include/asm/pgtable.h > > @@ -1120,6 +1120,9 @@ static inline bool arch_alloc_cma(gfp_t gfp_mask) > > return true; > > } > > > > +bool arch_hugepage_vma_revalidate(struct vm_area_struct *vma, unsigned long address); > > +#define arch_hugepage_vma_revalidate arch_hugepage_vma_revalidate > > + > > #endif /* CONFIG_ARM64_MTE_TAG_STORAGE */ > > #endif /* CONFIG_ARM64_MTE */ > > > > diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_tag_storage.c > > index ac7b9c9c585c..a99959b70573 100644 > > --- a/arch/arm64/kernel/mte_tag_storage.c > > +++ b/arch/arm64/kernel/mte_tag_storage.c > > @@ -636,3 +636,8 @@ void arch_alloc_page(struct page *page, int order, gfp_t gfp) > > if (tag_storage_enabled() && alloc_requires_tag_storage(gfp)) > > reserve_tag_storage(page, order, gfp); > > } > > + > > +bool arch_hugepage_vma_revalidate(struct vm_area_struct *vma, unsigned long address) > > +{ > > + return !(vma->vm_flags & VM_MTE); > > +} > > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h > > index f68865e19b0b..461e4322dff2 100644 > > --- a/include/linux/khugepaged.h > > +++ b/include/linux/khugepaged.h > > @@ -38,6 +38,11 @@ static inline void khugepaged_exit(struct mm_struct *mm) > > if (test_bit(MMF_VM_HUGEPAGE, &mm->flags)) > > __khugepaged_exit(mm); > > } > > + > > +#ifndef arch_hugepage_vma_revalidate > > +#define arch_hugepage_vma_revalidate(vma, address) 1 > > Please replace s/1/true as arch_hugepage_vma_revalidate() returns bool ? Yeah, that's strange, I don't know why I used 1 there. Will change it to true, thanks for spotting it. > > > +#endif > > Right, above construct is much better than __HAVE_ARCH_XXXX based one. Thanks! Alex > > > + > > #else /* CONFIG_TRANSPARENT_HUGEPAGE */ > > static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm) > > { > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index 2b219acb528e..cb9a9ddb4d86 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -935,6 +935,10 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, > > */ > > if (expect_anon && (!(*vmap)->anon_vma || !vma_is_anonymous(*vmap))) > > return SCAN_PAGE_ANON; > > + > > + if (!arch_hugepage_vma_revalidate(vma, address)) > > + return SCAN_VMA_CHECK; > > + > > return SCAN_SUCCEED; > > } > > > > Otherwise this LGTM.