Kernel: Add RegionTree::remove(Region&)

This allows clients to remove a region from the tree without reaching
into the RegionTree internals.

Kernel/Memory/AddressSpace.cpp

@@ -229,9 +229,7 @@ void AddressSpace::deallocate_region(Region& region)
 
 NonnullOwnPtr<Region> AddressSpace::take_region(Region& region)
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
-    auto did_remove = m_region_tree.regions().remove(region.vaddr().get());
+    auto did_remove = m_region_tree.remove(region);
     VERIFY(did_remove);
     return NonnullOwnPtr { NonnullOwnPtr<Region>::Adopt, region };
 }

Kernel/Memory/MemoryManager.cpp

@@ -1168,9 +1168,7 @@ bool MemoryManager::validate_user_stack(AddressSpace& space, VirtualAddress vadd
 void MemoryManager::unregister_kernel_region(Region& region)
 {
     VERIFY(region.is_kernel());
-    SpinlockLocker lock(s_mm_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
-    m_region_tree.regions().remove(region.vaddr().get());
+    m_region_tree.remove(region);
 }
 
 void MemoryManager::dump_kernel_regions()

Kernel/Memory/RegionTree.cpp

@@ -164,4 +164,10 @@ ErrorOr<NonnullOwnPtr<Memory::Region>> RegionTree::create_identity_mapped_region
     return region;
 }
 
+bool RegionTree::remove(Region& region)
+{
+    SpinlockLocker locker(m_lock);
+    return m_regions.remove(region.range().base().get());
+}
+
 }

Kernel/Memory/RegionTree.h

@@ -52,6 +52,8 @@ public:
     // FIXME: Access the region tree through a SpinlockProtected or similar.
     RecursiveSpinlock& get_lock() const { return m_lock; }
 
+    bool remove(Region&);
+
 private:
     ErrorOr<VirtualRange> allocate_range_anywhere(size_t size, size_t alignment = PAGE_SIZE);
     ErrorOr<VirtualRange> allocate_range_specific(VirtualAddress base, size_t size);