uprobes: Remove copy_vma()->uprobe_mmap()

Remove copy_vma()->uprobe_mmap(new_vma), it is absolutely wrong.

This new_vma was just initialized to represent the new unmapped
area, [vm_start, vm_end) was returned by get_unmapped_area() in
the caller.

This means that uprobe_mmap()->get_user_pages() will fail for
sure, simply because find_vma() can never succeed. And I
verified that sys_mremap()->mremap_to() indeed always fails with
the wrong ENOMEM code if [addr, addr+old_len] is probed.

And why this uprobe_mmap() was added? I believe the intent was
wrong. Note that the caller is going to do move_page_tables(),
all registered uprobes are already faulted in, we only change
the virtual addresses.

NOTE: However, somehow we need to close the race with
uprobe_register() which relies on map_info->vaddr. This needs
another fix I'll try to do later. Probably we need uprobe_mmap()
in move_vma() but we can not do this right now, this can confuse
uprobes_state.counter (which I still hope we are going to kill).

Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

mm/mmap.c

@@ -2418,9 +2418,6 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
 			if (new_vma->vm_file) {
 				get_file(new_vma->vm_file);
 
-				if (uprobe_mmap(new_vma))
-					goto out_free_mempol;
-
 				if (vma->vm_flags & VM_EXECUTABLE)
 					added_exe_file_vma(mm);
 			}