On Mon, 2012-04-16 at 17:34 +0200, Oleg Nesterov wrote:
> On 04/16, Peter Zijlstra wrote:
> >
> > Can't we 'optimize' read_opcode() by doing the pagefault_disable() +
> > __copy_from_user_inatomic() optimistically before going down the whole
> > gup()+lock+kmap path?
>
> Unlikely, the task is not current.
Easy enough to test that though.. and that should make the regular path
fast enough, no?
---
kernel/events/uprobes.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 985be4d..7f5d8c5 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -312,6 +312,15 @@ static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_
void *vaddr_new;
int ret;
+ if (mm == current->mm) {
+ pagefault_disable();
+ ret = __copy_from_user_inatomic(opcode, (void __user *)vaddr,
+ sizeof(*opcode));
+ pagefault_enable();
+ if (!ret)
+ return 0;
+ }
+
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL);
if (ret <= 0)
return ret;
--
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