arm: mm: enable HAVE_RCU_TABLE_FREE logic
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@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dann Frazier <dann.frazier@canonical.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 36d4798..eafe6ae 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -62,6 +62,7 @@
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_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->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 @@
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 @@
{
#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
}