From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753903Ab2H2Pdw (ORCPT ); Wed, 29 Aug 2012 11:33:52 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:48562 "EHLO e06smtp17.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752456Ab2H2Pdu (ORCPT ); Wed, 29 Aug 2012 11:33:50 -0400 From: Gerald Schaefer To: Andrew Morton , Andrea Arcangeli , Andi Kleen , Hugh Dickins , Hillf Danton Cc: linux-kernel@vger.kernel.org, Martin Schwidefsky , Heiko Carstens , Gerald Schaefer Subject: [RFC v2 PATCH 4/7] thp, s390: thp splitting backend for s390 Date: Wed, 29 Aug 2012 17:33:01 +0200 Message-Id: <1346254384-30046-5-git-send-email-gerald.schaefer@de.ibm.com> X-Mailer: git-send-email 1.7.11.5 In-Reply-To: <1346254384-30046-1-git-send-email-gerald.schaefer@de.ibm.com> References: <1346254384-30046-1-git-send-email-gerald.schaefer@de.ibm.com> x-cbid: 12082915-0542-0000-0000-000002DDC40C Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch is part of the architecture backend for thp on s390. It provides the functions related to thp splitting, including serialization against gup. Unlike other archs, pmdp_splitting_flush() cannot use a tlb flushing operation to serialize against gup on s390, because that wouldn't be stopped by the disabled IRQs. So instead, smp_call_function() is called with an empty function, which will have the expected effect. Signed-off-by: Gerald Schaefer --- arch/s390/include/asm/pgtable.h | 13 +++++++++++++ arch/s390/mm/gup.c | 11 ++++++++++- arch/s390/mm/pgtable.c | 18 ++++++++++++++++++ 3 files changed, 41 insertions(+), 1 deletion(-) diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 6bd7d74..c3f0775 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -347,6 +347,8 @@ extern struct page *vmemmap; #define _SEGMENT_ENTRY_LARGE 0x400 /* STE-format control, large page */ #define _SEGMENT_ENTRY_CO 0x100 /* change-recording override */ +#define _SEGMENT_ENTRY_SPLIT_BIT 0 /* THP splitting bit number */ +#define _SEGMENT_ENTRY_SPLIT (1UL << _SEGMENT_ENTRY_SPLIT_BIT) /* Page status table bits for virtualization */ #define RCP_ACC_BITS 0xf000000000000000UL @@ -506,6 +508,10 @@ static inline int pmd_bad(pmd_t pmd) return (pmd_val(pmd) & mask) != _SEGMENT_ENTRY; } +#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH +extern void pmdp_splitting_flush(struct vm_area_struct *vma, + unsigned long addr, pmd_t *pmdp); + static inline int pte_none(pte_t pte) { return (pte_val(pte) & _PAGE_INVALID) && !(pte_val(pte) & _PAGE_SWT); @@ -1159,6 +1165,13 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address) #define pte_offset_map(pmd, address) pte_offset_kernel(pmd, address) #define pte_unmap(pte) do { } while (0) +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static inline int pmd_trans_splitting(pmd_t pmd) +{ + return pmd_val(pmd) & _SEGMENT_ENTRY_SPLIT; +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + /* * 31 bit swap entry format: * A page-table entry has some bits we have to treat in a special way. diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c index 65cb06e..d34fd6e 100644 --- a/arch/s390/mm/gup.c +++ b/arch/s390/mm/gup.c @@ -115,7 +115,16 @@ static inline int gup_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, pmd = *pmdp; barrier(); next = pmd_addr_end(addr, end); - if (pmd_none(pmd)) + /* + * The pmd_trans_splitting() check below explains why + * pmdp_splitting_flush() has to serialize with + * smp_call_function() against our disabled IRQs, to stop + * this gup-fast code from running while we set the + * splitting bit in the pmd. Returning zero will take + * the slow path that will call wait_split_huge_page() + * if the pmd is still in splitting state. + */ + if (pmd_none(pmd) || pmd_trans_splitting(pmd)) return 0; if (unlikely(pmd_huge(pmd))) { if (!gup_huge_pmd(pmdp, pmd, addr, next, diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c index 18df31d..5a73522 100644 --- a/arch/s390/mm/pgtable.c +++ b/arch/s390/mm/pgtable.c @@ -866,3 +866,21 @@ bool kernel_page_present(struct page *page) return cc == 0; } #endif /* CONFIG_HIBERNATION && CONFIG_DEBUG_PAGEALLOC */ + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static void pmdp_splitting_flush_sync(void *arg) +{ + /* Simply deliver the interrupt */ +} + +void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmdp) +{ + VM_BUG_ON(address & ~HPAGE_PMD_MASK); + if (!test_and_set_bit(_SEGMENT_ENTRY_SPLIT_BIT, + (unsigned long *) pmdp)) { + /* need to serialize against gup-fast (IRQ disabled) */ + smp_call_function(pmdp_splitting_flush_sync, NULL, 1); + } +} +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ -- 1.7.11.5