In order to implement fast_get_user_pages we need to ensure that the page table walker is protected from page table pages being freed from under it. This patch enables HAVE_RCU_TABLE_FREE, any page table pages belonging to address spaces with multiple users will be call_rcu_sched freed. Meaning that disabling interrupts will block the free and protect the fast gup page walker. Signed-off-by: Steve Capper <steve.capper@xxxxxxxxxx> --- arch/arm/Kconfig | 1 + arch/arm/include/asm/tlb.h | 38 ++++++++++++++++++++++++++++++++++++-- 2 files changed, 37 insertions(+), 2 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index c49a775..cc740d2 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -60,6 +60,7 @@ config ARM select HAVE_PERF_EVENTS select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP + select HAVE_RCU_TABLE_FREE if (SMP && ARM_LPAE) select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_SYSCALL_TRACEPOINTS select HAVE_UID16 diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h index f1a0dac..3cadb72 100644 --- a/arch/arm/include/asm/tlb.h +++ b/arch/arm/include/asm/tlb.h @@ -35,12 +35,39 @@ #define MMU_GATHER_BUNDLE 8 +#ifdef CONFIG_HAVE_RCU_TABLE_FREE +static inline void __tlb_remove_table(void *_table) +{ + free_page_and_swap_cache((struct page *)_table); +} + +struct mmu_table_batch { + struct rcu_head rcu; + unsigned int nr; + void *tables[0]; +}; + +#define MAX_TABLE_BATCH \ + ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *)) + +extern void tlb_table_flush(struct mmu_gather *tlb); +extern void tlb_remove_table(struct mmu_gather *tlb, void *table); + +#define tlb_remove_entry(tlb, entry) tlb_remove_table(tlb, entry) +#else +#define tlb_remove_entry(tlb, entry) tlb_remove_page(tlb, entry) +#endif /* CONFIG_HAVE_RCU_TABLE_FREE */ + /* * TLB handling. This allows us to remove pages from the page * tables, and efficiently handle the TLB issues. */ struct mmu_gather { struct mm_struct *mm; +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + struct mmu_table_batch *batch; + unsigned int need_flush; +#endif unsigned int fullmm; struct vm_area_struct *vma; unsigned long start, end; @@ -101,6 +128,9 @@ static inline void __tlb_alloc_page(struct mmu_gather *tlb) static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb) { tlb_flush(tlb); +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + tlb_table_flush(tlb); +#endif } static inline void tlb_flush_mmu_free(struct mmu_gather *tlb) @@ -129,6 +159,10 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start tlb->pages = tlb->local; tlb->nr = 0; __tlb_alloc_page(tlb); + +#ifdef CONFIG_HAVE_RCU_TABLE_FREE + tlb->batch = NULL; +#endif } static inline void @@ -205,7 +239,7 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, tlb_add_flush(tlb, addr + SZ_1M); #endif - tlb_remove_page(tlb, pte); + tlb_remove_entry(tlb, pte); } static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, @@ -213,7 +247,7 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, { #ifdef CONFIG_ARM_LPAE tlb_add_flush(tlb, addr); - tlb_remove_page(tlb, virt_to_page(pmdp)); + tlb_remove_entry(tlb, virt_to_page(pmdp)); #endif } -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>