VM: add "vm_mmap()" helper function

This continues the theme started with vm_brk() and vm_munmap():
vm_mmap() does the same thing as do_mmap(), but additionally does the
required VM locking.

This uninlines (and rewrites it to be clearer) do_mmap(), which sadly
duplicates it in mm/mmap.c and mm/nommu.c.  But that way we don't have
to export our internal do_mmap_pgoff() function.

Some day we hopefully don't have to export do_mmap() either, if all
modular users can become the simpler vm_mmap() instead.  We're actually
very close to that already, with the notable exception of the (broken)
use in i810, and a couple of stragglers in binfmt_elf.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 3 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8beb9ce79364..1457be305fb1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6336,13 +6336,11 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
                 if (npages && !old.rmap) {
                         unsigned long userspace_addr;
 
-                        down_write(&current->mm->mmap_sem);
-                        userspace_addr = do_mmap(NULL, 0,
+                        userspace_addr = vm_mmap(NULL, 0,
                                                  npages * PAGE_SIZE,
                                                  PROT_READ | PROT_WRITE,
                                                  map_flags,
                                                  0);
-                        up_write(&current->mm->mmap_sem);
 
                         if (IS_ERR((void *)userspace_addr))
                                 return PTR_ERR((void *)userspace_addr);