Kernel: Set up Regions before adding them to a Process's AddressSpace

This reduces the amount of time in which not fully-initialized Regions
are present inside an AddressSpace's region tree.

Kernel/Memory/AddressSpace.cpp

@@ -146,16 +146,15 @@ ErrorOr<Region*> AddressSpace::try_allocate_split_region(Region const& source_re
 
     auto new_region = TRY(Region::try_create_user_accessible(
         range, source_region.vmobject(), offset_in_vmobject, move(region_name), source_region.access(), source_region.is_cacheable() ? Region::Cacheable::Yes : Region::Cacheable::No, source_region.is_shared()));
-    auto* region = TRY(add_region(move(new_region)));
-    region->set_syscall_region(source_region.is_syscall_region());
-    region->set_mmap(source_region.is_mmap());
-    region->set_stack(source_region.is_stack());
+    new_region->set_syscall_region(source_region.is_syscall_region());
+    new_region->set_mmap(source_region.is_mmap());
+    new_region->set_stack(source_region.is_stack());
     size_t page_offset_in_source_region = (offset_in_vmobject - source_region.offset_in_vmobject()) / PAGE_SIZE;
-    for (size_t i = 0; i < region->page_count(); ++i) {
+    for (size_t i = 0; i < new_region->page_count(); ++i) {
         if (source_region.should_cow(page_offset_in_source_region + i))
-            TRY(region->set_should_cow(i, true));
+            TRY(new_region->set_should_cow(i, true));
     }
-    return region;
+    return add_region(move(new_region));
 }
 
 ErrorOr<Region*> AddressSpace::allocate_region(VirtualRange const& range, StringView name, int prot, AllocationStrategy strategy)
@@ -191,16 +190,15 @@ ErrorOr<Region*> AddressSpace::allocate_region_with_vmobject(VirtualRange const&
     if (!name.is_null())
         region_name = TRY(KString::try_create(name));
     auto region = TRY(Region::try_create_user_accessible(range, move(vmobject), offset_in_vmobject, move(region_name), prot_to_region_access_flags(prot), Region::Cacheable::Yes, shared));
-    auto* added_region = TRY(add_region(move(region)));
     if (prot == PROT_NONE) {
         // For PROT_NONE mappings, we don't have to set up any page table mappings.
         // We do still need to attach the region to the page_directory though.
         SpinlockLocker mm_locker(s_mm_lock);
-        added_region->set_page_directory(page_directory());
+        region->set_page_directory(page_directory());
     } else {
-        TRY(added_region->map(page_directory(), ShouldFlushTLB::No));
+        TRY(region->map(page_directory(), ShouldFlushTLB::No));
     }
-    return added_region;
+    return add_region(move(region));
 }
 
 void AddressSpace::deallocate_region(Region& region)

Kernel/Syscalls/fork.cpp

@@ -106,8 +106,8 @@ ErrorOr<FlatPtr> Process::sys$fork(RegisterState& regs)
         for (auto& region : address_space().regions()) {
             dbgln_if(FORK_DEBUG, "fork: cloning Region({}) '{}' @ {}", region, region->name(), region->vaddr());
             auto region_clone = TRY(region->try_clone());
+            TRY(region_clone->map(child->address_space().page_directory(), Memory::ShouldFlushTLB::No));
             auto* child_region = TRY(child->address_space().add_region(move(region_clone)));
-            TRY(child_region->map(child->address_space().page_directory(), Memory::ShouldFlushTLB::No));
 
             if (region == m_master_tls_region.unsafe_ptr())
                 child->m_master_tls_region = child_region;