Let's allow people to tweak faultaround in runtime.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
mm/memory.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 61 insertions(+), 7 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 3f17a60e817f..e2d54e818c5b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -60,6 +60,7 @@
#include <linux/migrate.h>
#include <linux/string.h>
#include <linux/dma-debug.h>
+#include <linux/debugfs.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
@@ -3344,8 +3345,63 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address,
}
#define FAULT_AROUND_ORDER 4
-#define FAULT_AROUND_PAGES (1UL << FAULT_AROUND_ORDER)
-#define FAULT_AROUND_MASK ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1)
+
+#ifdef CONFIG_DEBUG_FS
+static unsigned int fault_around_order = FAULT_AROUND_ORDER;
+
+static int fault_around_order_get(void *data, u64 *val)
+{
+ *val = fault_around_order;
+ return 0;
+}
+
+static int fault_around_order_set(void *data, u64 val)
+{
+ BUILD_BUG_ON((1UL << FAULT_AROUND_ORDER) > PTRS_PER_PTE);
+ if (1UL << val > PTRS_PER_PTE)
+ return -EINVAL;
+ fault_around_order = val;
+ return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(fault_around_order_fops,
+ fault_around_order_get, fault_around_order_set, "%llu\n");
+
+static int __init fault_around_debugfs(void)
+{
+ void *ret;
+
+ ret = debugfs_create_file("fault_around_order", 0644, NULL, NULL,
+ &fault_around_order_fops);
+ if (!ret)
+ pr_warning("Failed to create fault_around_order in debugfs");
+ return 0;
+}
+late_initcall(fault_around_debugfs);
+
+static inline unsigned long fault_around_pages(void)
+{
+ return 1UL << fault_around_order;
+}
+
+static inline unsigned long fault_around_mask(void)
+{
+ return ~((1UL << (PAGE_SHIFT + fault_around_order)) - 1);
+}
+#else
+static inline unsigned long fault_around_pages(void)
+{
+ unsigned long nr_pages;
+
+ nr_pages = 1UL << FAULT_AROUND_ORDER;
+ BUILD_BUG_ON(nr_pages > PTRS_PER_PTE);
+ return nr_pages;
+}
+
+static inline unsigned long fault_around_mask(void)
+{
+ return ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1);
+}
+#endif
static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
pte_t *pte, pgoff_t pgoff, unsigned int flags)
@@ -3355,21 +3411,19 @@ static void do_fault_around(struct vm_area_struct *vma, unsigned long address,
struct vm_fault vmf;
int off;
- BUILD_BUG_ON(FAULT_AROUND_PAGES > PTRS_PER_PTE);
-
- start_addr = max(address & FAULT_AROUND_MASK, vma->vm_start);
+ start_addr = max(address & fault_around_mask(), vma->vm_start);
off = ((address - start_addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
pte -= off;
pgoff -= off;
/*
* max_pgoff is either end of page table or end of vma
- * or FAULT_AROUND_PAGES from pgoff, depending what is neast.
+ * or fault_around_pages() from pgoff, depending what is neast.
*/
max_pgoff = pgoff - ((start_addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
PTRS_PER_PTE - 1;
max_pgoff = min3(max_pgoff, vma_pages(vma) + vma->vm_pgoff - 1,
- pgoff + FAULT_AROUND_PAGES - 1);
+ pgoff + fault_around_pages() - 1);
/* Check if it makes any sense to call ->map_pages */
while (!pte_none(*pte)) {
--
1.9.0
--
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