Andrew Morton wrote:
> On Mon, 19 May 2014 16:23:07 -0700 (PDT) Hugh Dickins <hughd@xxxxxxxxxx> wrote:
>
> > Shouldn't FAULT_AROUND_ORDER and fault_around_order be changed to be
> > the order of the fault-around size in bytes, and fault_around_pages()
> > use 1UL << (fault_around_order - PAGE_SHIFT)
>
> Yes. And shame on me for missing it (this time!) at review.
>
> There's still time to fix this. Patches, please.
Here it is. Made at 3.30 AM, build tested only.
I'll sign it off tomorrow after testing.
diff --git a/mm/memory.c b/mm/memory.c
index 037b812a9531..9d6941c9a9e4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3402,62 +3402,62 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address,
update_mmu_cache(vma, address, pte);
}
-#define FAULT_AROUND_ORDER 4
+#define FAULT_AROUND_BYTES 65536
#ifdef CONFIG_DEBUG_FS
-static unsigned int fault_around_order = FAULT_AROUND_ORDER;
+static unsigned int fault_around_bytes = FAULT_AROUND_BYTES;
-static int fault_around_order_get(void *data, u64 *val)
+static int fault_around_bytes_get(void *data, u64 *val)
{
- *val = fault_around_order;
+ *val = fault_around_bytes;
return 0;
}
-static int fault_around_order_set(void *data, u64 val)
+static int fault_around_bytes_set(void *data, u64 val)
{
- BUILD_BUG_ON((1UL << FAULT_AROUND_ORDER) > PTRS_PER_PTE);
- if (1UL << val > PTRS_PER_PTE)
+ BUILD_BUG_ON(FAULT_AROUND_BYTES / PAGE_SIZE > PTRS_PER_PTE);
+ if (val / PAGE_SIZE > PTRS_PER_PTE)
return -EINVAL;
- fault_around_order = val;
+ fault_around_bytes = val;
return 0;
}
-DEFINE_SIMPLE_ATTRIBUTE(fault_around_order_fops,
- fault_around_order_get, fault_around_order_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops,
+ fault_around_bytes_get, fault_around_bytes_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);
+ ret = debugfs_create_file("fault_around_bytes", 0644, NULL, NULL,
+ &fault_around_bytes_fops);
if (!ret)
- pr_warn("Failed to create fault_around_order in debugfs");
+ pr_warn("Failed to create fault_around_bytes in debugfs");
return 0;
}
late_initcall(fault_around_debugfs);
static inline unsigned long fault_around_pages(void)
{
- return 1UL << fault_around_order;
+ return fault_around_bytes / PAGE_SIZE;
}
static inline unsigned long fault_around_mask(void)
{
- return ~((1UL << (PAGE_SHIFT + fault_around_order)) - 1);
+ return ~(round_down(fault_around_bytes, PAGE_SIZE) - 1);
}
#else
static inline unsigned long fault_around_pages(void)
{
unsigned long nr_pages;
- nr_pages = 1UL << FAULT_AROUND_ORDER;
+ nr_pages = FAULT_AROUND_BYTES / PAGE_SIZE;
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);
+ return ~(round_down(FAULT_AROUND_BYTES, PAGE_SIZE) - 1);
}
#endif
@@ -3515,7 +3515,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
* if page by the offset is not ready to be mapped (cold cache or
* something).
*/
- if (vma->vm_ops->map_pages) {
+ if (vma->vm_ops->map_pages && fault_around_pages() > 1) {
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
do_fault_around(vma, address, pte, pgoff, flags);
if (!pte_same(*pte, orig_pte))
--
Kirill A. Shutemov
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