Kernel: Wrap RegionTree objects in SpinlockProtected

This makes locking them much more straightforward, and we can remove
a bunch of confusing use of AddressSpace::m_lock. That lock will also
be converted to use of SpinlockProtected in a subsequent patch.

9 files changed, 258 insertions, 241 deletions

diff --git a/Kernel/Coredump.cpp b/Kernel/Coredump.cpp
index 1348f232f8..1c7f3add12 100644
--- a/Kernel/Coredump.cpp
+++ b/Kernel/Coredump.cpp
@@ -46,16 +46,18 @@ Coredump::Coredump(NonnullLockRefPtr<Process> process, NonnullLockRefPtr<OpenFil
     , m_description(move(description))
 {
     m_num_program_headers = 0;
-    for ([[maybe_unused]] auto& region : m_process->address_space().regions()) {
+    m_process->address_space().region_tree().with([&](auto& region_tree) {
+        for (auto& region : region_tree.regions()) {
 #if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
-        if (looks_like_userspace_heap_region(region))
-            continue;
+            if (looks_like_userspace_heap_region(region))
+                continue;
 #endif
 
-        if (region.access() == Memory::Region::Access::None)
-            continue;
-        ++m_num_program_headers;
-    }
+            if (region.access() == Memory::Region::Access::None)
+                continue;
+            ++m_num_program_headers;
+        }
+    });
     ++m_num_program_headers; // +1 for NOTE segment
 }
 
@@ -133,37 +135,39 @@ ErrorOr<void> Coredump::write_elf_header()
 ErrorOr<void> Coredump::write_program_headers(size_t notes_size)
 {
     size_t offset = sizeof(ElfW(Ehdr)) + m_num_program_headers * sizeof(ElfW(Phdr));
-    for (auto& region : m_process->address_space().regions()) {
+    m_process->address_space().region_tree().with([&](auto& region_tree) {
+        for (auto& region : region_tree.regions()) {
 
 #if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
-        if (looks_like_userspace_heap_region(region))
-            continue;
+            if (looks_like_userspace_heap_region(region))
+                continue;
 #endif
 
-        if (region.access() == Memory::Region::Access::None)
-            continue;
+            if (region.access() == Memory::Region::Access::None)
+                continue;
 
-        ElfW(Phdr) phdr {};
+            ElfW(Phdr) phdr {};
 
-        phdr.p_type = PT_LOAD;
-        phdr.p_offset = offset;
-        phdr.p_vaddr = region.vaddr().get();
-        phdr.p_paddr = 0;
+            phdr.p_type = PT_LOAD;
+            phdr.p_offset = offset;
+            phdr.p_vaddr = region.vaddr().get();
+            phdr.p_paddr = 0;
 
-        phdr.p_filesz = region.page_count() * PAGE_SIZE;
-        phdr.p_memsz = region.page_count() * PAGE_SIZE;
-        phdr.p_align = 0;
+            phdr.p_filesz = region.page_count() * PAGE_SIZE;
+            phdr.p_memsz = region.page_count() * PAGE_SIZE;
+            phdr.p_align = 0;
 
-        phdr.p_flags = region.is_readable() ? PF_R : 0;
-        if (region.is_writable())
-            phdr.p_flags |= PF_W;
-        if (region.is_executable())
-            phdr.p_flags |= PF_X;
+            phdr.p_flags = region.is_readable() ? PF_R : 0;
+            if (region.is_writable())
+                phdr.p_flags |= PF_W;
+            if (region.is_executable())
+                phdr.p_flags |= PF_X;
 
-        offset += phdr.p_filesz;
+            offset += phdr.p_filesz;
 
-        [[maybe_unused]] auto rc = m_description->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(&phdr)), sizeof(ElfW(Phdr)));
-    }
+            [[maybe_unused]] auto rc = m_description->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(&phdr)), sizeof(ElfW(Phdr)));
+        }
+    });
 
     ElfW(Phdr) notes_pheader {};
     notes_pheader.p_type = PT_NOTE;
@@ -184,36 +188,38 @@ ErrorOr<void> Coredump::write_regions()
 {
     u8 zero_buffer[PAGE_SIZE] = {};
 
-    for (auto& region : m_process->address_space().regions()) {
-        VERIFY(!region.is_kernel());
+    return m_process->address_space().region_tree().with([&](auto& region_tree) -> ErrorOr<void> {
+        for (auto& region : region_tree.regions()) {
+            VERIFY(!region.is_kernel());
 
 #if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
-        if (looks_like_userspace_heap_region(region))
-            continue;
+            if (looks_like_userspace_heap_region(region))
+                continue;
 #endif
 
-        if (region.access() == Memory::Region::Access::None)
-            continue;
-
-        // If we crashed in the middle of mapping in Regions, they do not have a page directory yet, and will crash on a remap() call
-        if (!region.is_mapped())
-            continue;
-
-        region.set_readable(true);
-        region.remap();
-
-        for (size_t i = 0; i < region.page_count(); i++) {
-            auto page = region.physical_page(i);
-            auto src_buffer = [&]() -> ErrorOr<UserOrKernelBuffer> {
-                if (page)
-                    return UserOrKernelBuffer::for_user_buffer(reinterpret_cast<uint8_t*>((region.vaddr().as_ptr() + (i * PAGE_SIZE))), PAGE_SIZE);
-                // If the current page is not backed by a physical page, we zero it in the coredump file.
-                return UserOrKernelBuffer::for_kernel_buffer(zero_buffer);
-            }();
-            TRY(m_description->write(src_buffer.value(), PAGE_SIZE));
+            if (region.access() == Memory::Region::Access::None)
+                continue;
+
+            // If we crashed in the middle of mapping in Regions, they do not have a page directory yet, and will crash on a remap() call
+            if (!region.is_mapped())
+                continue;
+
+            region.set_readable(true);
+            region.remap();
+
+            for (size_t i = 0; i < region.page_count(); i++) {
+                auto page = region.physical_page(i);
+                auto src_buffer = [&]() -> ErrorOr<UserOrKernelBuffer> {
+                    if (page)
+                        return UserOrKernelBuffer::for_user_buffer(reinterpret_cast<uint8_t*>((region.vaddr().as_ptr() + (i * PAGE_SIZE))), PAGE_SIZE);
+                    // If the current page is not backed by a physical page, we zero it in the coredump file.
+                    return UserOrKernelBuffer::for_kernel_buffer(zero_buffer);
+                }();
+                TRY(m_description->write(src_buffer.value(), PAGE_SIZE));
+            }
         }
-    }
-    return {};
+        return {};
+    });
 }
 
 ErrorOr<void> Coredump::write_notes_segment(ReadonlyBytes notes_segment)
@@ -273,33 +279,35 @@ ErrorOr<void> Coredump::create_notes_threads_data(auto& builder) const
 ErrorOr<void> Coredump::create_notes_regions_data(auto& builder) const
 {
     size_t region_index = 0;
-    for (auto const& region : m_process->address_space().regions()) {
+    return m_process->address_space().region_tree().with([&](auto& region_tree) -> ErrorOr<void> {
+        for (auto const& region : region_tree.regions()) {
 
 #if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
-        if (looks_like_userspace_heap_region(region))
-            continue;
+            if (looks_like_userspace_heap_region(region))
+                continue;
 #endif
 
-        if (region.access() == Memory::Region::Access::None)
-            continue;
+            if (region.access() == Memory::Region::Access::None)
+                continue;
 
-        ELF::Core::MemoryRegionInfo info {};
-        info.header.type = ELF::Core::NotesEntryHeader::Type::MemoryRegionInfo;
+            ELF::Core::MemoryRegionInfo info {};
+            info.header.type = ELF::Core::NotesEntryHeader::Type::MemoryRegionInfo;
 
-        info.region_start = region.vaddr().get();
-        info.region_end = region.vaddr().offset(region.size()).get();
-        info.program_header_index = region_index++;
+            info.region_start = region.vaddr().get();
+            info.region_end = region.vaddr().offset(region.size()).get();
+            info.program_header_index = region_index++;
 
-        TRY(builder.append_bytes(ReadonlyBytes { (void*)&info, sizeof(info) }));
+            TRY(builder.append_bytes(ReadonlyBytes { (void*)&info, sizeof(info) }));
 
-        // NOTE: The region name *is* null-terminated, so the following is ok:
-        auto name = region.name();
-        if (name.is_empty())
-            TRY(builder.append('\0'));
-        else
-            TRY(builder.append(name.characters_without_null_termination(), name.length() + 1));
-    }
-    return {};
+            // NOTE: The region name *is* null-terminated, so the following is ok:
+            auto name = region.name();
+            if (name.is_empty())
+                TRY(builder.append('\0'));
+            else
+                TRY(builder.append(name.characters_without_null_termination(), name.length() + 1));
+        }
+        return {};
+    });
 }
 
 ErrorOr<void> Coredump::create_notes_metadata_data(auto& builder) const
diff --git a/Kernel/Memory/AddressSpace.cpp b/Kernel/Memory/AddressSpace.cpp
index cc2a765a40..f215e572cd 100644
--- a/Kernel/Memory/AddressSpace.cpp
+++ b/Kernel/Memory/AddressSpace.cpp
@@ -25,7 +25,7 @@ ErrorOr<NonnullOwnPtr<AddressSpace>> AddressSpace::try_create(AddressSpace const
 
     VirtualRange total_range = [&]() -> VirtualRange {
         if (parent)
-            return parent->m_region_tree.total_range();
+            return parent->m_total_range;
         constexpr FlatPtr userspace_range_base = USER_RANGE_BASE;
         FlatPtr const userspace_range_ceiling = USER_RANGE_CEILING;
         size_t random_offset = (get_fast_random<u8>() % 2 * MiB) & PAGE_MASK;
@@ -40,7 +40,8 @@ ErrorOr<NonnullOwnPtr<AddressSpace>> AddressSpace::try_create(AddressSpace const
 
 AddressSpace::AddressSpace(NonnullLockRefPtr<PageDirectory> page_directory, VirtualRange total_range)
     : m_page_directory(move(page_directory))
-    , m_region_tree(total_range)
+    , m_total_range(total_range)
+    , m_region_tree(LockRank::None, total_range)
 {
 }
 
@@ -148,8 +149,10 @@ ErrorOr<Region*> AddressSpace::try_allocate_split_region(Region const& source_re
         if (source_region.should_cow(page_offset_in_source_region + i))
             TRY(new_region->set_should_cow(i, true));
     }
-    SpinlockLocker locker(m_lock);
-    TRY(m_region_tree.place_specifically(*new_region, range));
+    TRY(m_region_tree.with([&](auto& region_tree) -> ErrorOr<void> {
+        TRY(region_tree.place_specifically(*new_region, range));
+        return {};
+    }));
     return new_region.leak_ptr();
 }
 
@@ -164,11 +167,14 @@ ErrorOr<Region*> AddressSpace::allocate_region(RandomizeVirtualAddress randomize
         region_name = TRY(KString::try_create(name));
     auto vmobject = TRY(AnonymousVMObject::try_create_with_size(size, strategy));
     auto region = TRY(Region::create_unplaced(move(vmobject), 0, move(region_name), prot_to_region_access_flags(prot)));
-    if (requested_address.is_null()) {
-        TRY(m_region_tree.place_anywhere(*region, randomize_virtual_address, size, alignment));
-    } else {
-        TRY(m_region_tree.place_specifically(*region, VirtualRange { requested_address, size }));
-    }
+    TRY(m_region_tree.with([&](auto& region_tree) -> ErrorOr<void> {
+        if (requested_address.is_null()) {
+            TRY(region_tree.place_anywhere(*region, randomize_virtual_address, size, alignment));
+        } else {
+            TRY(region_tree.place_specifically(*region, VirtualRange { requested_address, size }));
+        }
+        return {};
+    }));
     TRY(region->map(page_directory(), ShouldFlushTLB::No));
     return region.leak_ptr();
 }
@@ -204,29 +210,29 @@ ErrorOr<Region*> AddressSpace::allocate_region_with_vmobject(RandomizeVirtualAdd
 
     auto region = TRY(Region::create_unplaced(move(vmobject), offset_in_vmobject, move(region_name), prot_to_region_access_flags(prot), Region::Cacheable::Yes, shared));
 
-    SpinlockLocker locker(m_lock);
-
-    if (requested_address.is_null())
-        TRY(m_region_tree.place_anywhere(*region, randomize_virtual_address, size, alignment));
-    else
-        TRY(m_region_tree.place_specifically(*region, VirtualRange { VirtualAddress { requested_address }, size }));
-
-    ArmedScopeGuard remove_region_from_tree_on_failure = [this, &region]() {
-        // At this point the region is already part of the Process region tree, so we have to make sure
-        // we remove it from the tree before returning an error, or else the Region tree will contain
-        // a dangling pointer to the free'd Region instance
-        m_region_tree.remove(*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.
-        region->set_page_directory(page_directory());
-    } else {
-        TRY(region->map(page_directory(), ShouldFlushTLB::No));
-    }
-    remove_region_from_tree_on_failure.disarm();
-    return region.leak_ptr();
+    return m_region_tree.with([&](auto& region_tree) -> ErrorOr<Region*> {
+        if (requested_address.is_null())
+            TRY(region_tree.place_anywhere(*region, randomize_virtual_address, size, alignment));
+        else
+            TRY(region_tree.place_specifically(*region, VirtualRange { VirtualAddress { requested_address }, size }));
+
+        ArmedScopeGuard remove_region_from_tree_on_failure = [&] {
+            // At this point the region is already part of the Process region tree, so we have to make sure
+            // we remove it from the tree before returning an error, or else the Region tree will contain
+            // a dangling pointer to the free'd Region instance
+            region_tree.remove(*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.
+            region->set_page_directory(page_directory());
+        } else {
+            TRY(region->map(page_directory(), ShouldFlushTLB::No));
+        }
+        remove_region_from_tree_on_failure.disarm();
+        return region.leak_ptr();
+    });
 }
 
 void AddressSpace::deallocate_region(Region& region)
@@ -236,16 +242,14 @@ void AddressSpace::deallocate_region(Region& region)
 
 NonnullOwnPtr<Region> AddressSpace::take_region(Region& region)
 {
-    auto did_remove = m_region_tree.remove(region);
+    auto did_remove = m_region_tree.with([&](auto& region_tree) { return region_tree.remove(region); });
     VERIFY(did_remove);
     return NonnullOwnPtr { NonnullOwnPtr<Region>::Adopt, region };
 }
 
 Region* AddressSpace::find_region_from_range(VirtualRange const& range)
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
-    auto* found_region = m_region_tree.regions().find(range.base().get());
+    auto* found_region = m_region_tree.with([&](auto& region_tree) { return region_tree.regions().find(range.base().get()); });
     if (!found_region)
         return nullptr;
     auto& region = *found_region;
@@ -257,7 +261,9 @@ Region* AddressSpace::find_region_from_range(VirtualRange const& range)
 
 Region* AddressSpace::find_region_containing(VirtualRange const& range)
 {
-    return m_region_tree.find_region_containing(range);
+    return m_region_tree.with([&](auto& region_tree) {
+        return region_tree.find_region_containing(range);
+    });
 }
 
 ErrorOr<Vector<Region*, 4>> AddressSpace::find_regions_intersecting(VirtualRange const& range)
@@ -265,24 +271,23 @@ ErrorOr<Vector<Region*, 4>> AddressSpace::find_regions_intersecting(VirtualRange
     Vector<Region*, 4> regions = {};
     size_t total_size_collected = 0;
 
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
-
-    auto* found_region = m_region_tree.regions().find_largest_not_above(range.base().get());
-    if (!found_region)
-        return regions;
-    for (auto iter = m_region_tree.regions().begin_from(*found_region); !iter.is_end(); ++iter) {
-        auto const& iter_range = (*iter).range();
-        if (iter_range.base() < range.end() && iter_range.end() > range.base()) {
-            TRY(regions.try_append(&*iter));
-
-            total_size_collected += (*iter).size() - iter_range.intersect(range).size();
-            if (total_size_collected == range.size())
-                break;
+    return m_region_tree.with([&](auto& region_tree) -> ErrorOr<Vector<Region*, 4>> {
+        auto* found_region = region_tree.regions().find_largest_not_above(range.base().get());
+        if (!found_region)
+            return regions;
+        for (auto iter = region_tree.regions().begin_from(*found_region); !iter.is_end(); ++iter) {
+            auto const& iter_range = (*iter).range();
+            if (iter_range.base() < range.end() && iter_range.end() > range.base()) {
+                TRY(regions.try_append(&*iter));
+
+                total_size_collected += (*iter).size() - iter_range.intersect(range).size();
+                if (total_size_collected == range.size())
+                    break;
+            }
         }
-    }
 
-    return regions;
+        return regions;
+    });
 }
 
 // Carve out a virtual address range from a region and return the two regions on either side
@@ -316,61 +321,63 @@ void AddressSpace::dump_regions()
     dbgln("BEGIN{}         END{}        SIZE{}       ACCESS NAME",
         addr_padding, addr_padding, addr_padding);
 
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
-
-    for (auto const& region : m_region_tree.regions()) {
-        dbgln("{:p} -- {:p} {:p} {:c}{:c}{:c}{:c}{:c}{:c} {}", region.vaddr().get(), region.vaddr().offset(region.size() - 1).get(), region.size(),
-            region.is_readable() ? 'R' : ' ',
-            region.is_writable() ? 'W' : ' ',
-            region.is_executable() ? 'X' : ' ',
-            region.is_shared() ? 'S' : ' ',
-            region.is_stack() ? 'T' : ' ',
-            region.is_syscall_region() ? 'C' : ' ',
-            region.name());
-    }
+    m_region_tree.with([&](auto& region_tree) {
+        for (auto const& region : region_tree.regions()) {
+            dbgln("{:p} -- {:p} {:p} {:c}{:c}{:c}{:c}{:c}{:c} {}", region.vaddr().get(), region.vaddr().offset(region.size() - 1).get(), region.size(),
+                region.is_readable() ? 'R' : ' ',
+                region.is_writable() ? 'W' : ' ',
+                region.is_executable() ? 'X' : ' ',
+                region.is_shared() ? 'S' : ' ',
+                region.is_stack() ? 'T' : ' ',
+                region.is_syscall_region() ? 'C' : ' ',
+                region.name());
+        }
+    });
     MM.dump_kernel_regions();
 }
 
 void AddressSpace::remove_all_regions(Badge<Process>)
 {
     VERIFY(Thread::current() == g_finalizer);
-    SpinlockLocker locker(m_lock);
     {
         SpinlockLocker pd_locker(m_page_directory->get_lock());
         SpinlockLocker mm_locker(s_mm_lock);
-        SpinlockLocker tree_locker(m_region_tree.get_lock());
-        for (auto& region : m_region_tree.regions())
-            region.unmap_with_locks_held(ShouldFlushTLB::No, pd_locker, mm_locker);
+        m_region_tree.with([&](auto& region_tree) {
+            for (auto& region : region_tree.regions())
+                region.unmap_with_locks_held(ShouldFlushTLB::No, pd_locker, mm_locker);
+        });
     }
 
-    m_region_tree.delete_all_regions_assuming_they_are_unmapped();
+    m_region_tree.with([&](auto& region_tree) {
+        region_tree.delete_all_regions_assuming_they_are_unmapped();
+    });
 }
 
 size_t AddressSpace::amount_dirty_private() const
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
     // FIXME: This gets a bit more complicated for Regions sharing the same underlying VMObject.
     //        The main issue I'm thinking of is when the VMObject has physical pages that none of the Regions are mapping.
     //        That's probably a situation that needs to be looked at in general.
     size_t amount = 0;
-    for (auto const& region : m_region_tree.regions()) {
-        if (!region.is_shared())
-            amount += region.amount_dirty();
-    }
+    m_region_tree.with([&](auto& region_tree) {
+        for (auto const& region : region_tree.regions()) {
+            if (!region.is_shared())
+                amount += region.amount_dirty();
+        }
+    });
     return amount;
 }
 
 ErrorOr<size_t> AddressSpace::amount_clean_inode() const
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
-    HashTable<InodeVMObject const*> vmobjects;
-    for (auto const& region : m_region_tree.regions()) {
-        if (region.vmobject().is_inode())
-            TRY(vmobjects.try_set(&static_cast<InodeVMObject const&>(region.vmobject())));
-    }
+    HashTable<LockRefPtr<InodeVMObject>> vmobjects;
+    TRY(m_region_tree.with([&](auto& region_tree) -> ErrorOr<void> {
+        for (auto const& region : region_tree.regions()) {
+            if (region.vmobject().is_inode())
+                TRY(vmobjects.try_set(&static_cast<InodeVMObject const&>(region.vmobject())));
+        }
+        return {};
+    }));
     size_t amount = 0;
     for (auto& vmobject : vmobjects)
         amount += vmobject->amount_clean();
@@ -379,69 +386,68 @@ ErrorOr<size_t> AddressSpace::amount_clean_inode() const
 
 size_t AddressSpace::amount_virtual() const
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
     size_t amount = 0;
-    for (auto const& region : m_region_tree.regions()) {
-        amount += region.size();
-    }
+    m_region_tree.with([&](auto& region_tree) {
+        for (auto const& region : region_tree.regions()) {
+            amount += region.size();
+        }
+    });
     return amount;
 }
 
 size_t AddressSpace::amount_resident() const
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
     // FIXME: This will double count if multiple regions use the same physical page.
     size_t amount = 0;
-    for (auto const& region : m_region_tree.regions()) {
-        amount += region.amount_resident();
-    }
+    m_region_tree.with([&](auto& region_tree) {
+        for (auto const& region : region_tree.regions()) {
+            amount += region.amount_resident();
+        }
+    });
     return amount;
 }
 
 size_t AddressSpace::amount_shared() const
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
     // FIXME: This will double count if multiple regions use the same physical page.
     // FIXME: It doesn't work at the moment, since it relies on PhysicalPage ref counts,
     //        and each PhysicalPage is only reffed by its VMObject. This needs to be refactored
     //        so that every Region contributes +1 ref to each of its PhysicalPages.
     size_t amount = 0;
-    for (auto const& region : m_region_tree.regions()) {
-        amount += region.amount_shared();
-    }
+    m_region_tree.with([&](auto& region_tree) {
+        for (auto const& region : region_tree.regions()) {
+            amount += region.amount_shared();
+        }
+    });
     return amount;
 }
 
 size_t AddressSpace::amount_purgeable_volatile() const
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
     size_t amount = 0;
-    for (auto const& region : m_region_tree.regions()) {
-        if (!region.vmobject().is_anonymous())
-            continue;
-        auto const& vmobject = static_cast<AnonymousVMObject const&>(region.vmobject());
-        if (vmobject.is_purgeable() && vmobject.is_volatile())
-            amount += region.amount_resident();
-    }
+    m_region_tree.with([&](auto& region_tree) {
+        for (auto const& region : region_tree.regions()) {
+            if (!region.vmobject().is_anonymous())
+                continue;
+            auto const& vmobject = static_cast<AnonymousVMObject const&>(region.vmobject());
+            if (vmobject.is_purgeable() && vmobject.is_volatile())
+                amount += region.amount_resident();
+        }
+    });
     return amount;
 }
 
 size_t AddressSpace::amount_purgeable_nonvolatile() const
 {
-    SpinlockLocker lock(m_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
     size_t amount = 0;
-    for (auto const& region : m_region_tree.regions()) {
+    m_region_tree.with([&](auto& region_tree) {
+    for (auto const& region : region_tree.regions()) {
         if (!region.vmobject().is_anonymous())
             continue;
         auto const& vmobject = static_cast<AnonymousVMObject const&>(region.vmobject());
         if (vmobject.is_purgeable() && !vmobject.is_volatile())
             amount += region.amount_resident();
-    }
+    } });
     return amount;
 }
 
diff --git a/Kernel/Memory/AddressSpace.h b/Kernel/Memory/AddressSpace.h
index e07cb3988a..23f7c7a76b 100644
--- a/Kernel/Memory/AddressSpace.h
+++ b/Kernel/Memory/AddressSpace.h
@@ -10,6 +10,7 @@
 #include <AK/RedBlackTree.h>
 #include <AK/Vector.h>
 #include <Kernel/Library/LockWeakPtr.h>
+#include <Kernel/Locking/SpinlockProtected.h>
 #include <Kernel/Memory/AllocationStrategy.h>
 #include <Kernel/Memory/PageDirectory.h>
 #include <Kernel/Memory/Region.h>
@@ -26,8 +27,8 @@ public:
     PageDirectory& page_directory() { return *m_page_directory; }
     PageDirectory const& page_directory() const { return *m_page_directory; }
 
-    auto& regions() { return m_region_tree.regions(); }
-    auto const& regions() const { return m_region_tree.regions(); }
+    SpinlockProtected<RegionTree>& region_tree() { return m_region_tree; }
+    SpinlockProtected<RegionTree> const& region_tree() const { return m_region_tree; }
 
     void dump_regions();
 
@@ -62,8 +63,6 @@ public:
     size_t amount_purgeable_volatile() const;
     size_t amount_purgeable_nonvolatile() const;
 
-    auto& region_tree() { return m_region_tree; }
-
 private:
     AddressSpace(NonnullLockRefPtr<PageDirectory>, VirtualRange total_range);
 
@@ -71,7 +70,11 @@ private:
 
     LockRefPtr<PageDirectory> m_page_directory;
 
-    RegionTree m_region_tree;
+    // NOTE: The total range is also in the RegionTree, but since it never changes,
+    //       it's nice to have it in a place where we can access it without locking.
+    VirtualRange m_total_range;
+
+    SpinlockProtected<RegionTree> m_region_tree;
 
     bool m_enforces_syscall_regions { false };
 };
diff --git a/Kernel/Memory/MemoryManager.cpp b/Kernel/Memory/MemoryManager.cpp
index a2aaf67cf5..01d73bc959 100644
--- a/Kernel/Memory/MemoryManager.cpp
+++ b/Kernel/Memory/MemoryManager.cpp
@@ -83,7 +83,7 @@ static UNMAP_AFTER_INIT VirtualRange kernel_virtual_range()
 }
 
 UNMAP_AFTER_INIT MemoryManager::MemoryManager()
-    : m_region_tree(kernel_virtual_range())
+    : m_region_tree(LockRank::None, kernel_virtual_range())
 {
     s_the = this;
 
@@ -434,13 +434,13 @@ UNMAP_AFTER_INIT void MemoryManager::initialize_physical_pages()
         // Carve out the whole page directory covering the kernel image to make MemoryManager::initialize_physical_pages() happy
         FlatPtr start_of_range = ((FlatPtr)start_of_kernel_image & ~(FlatPtr)0x1fffff);
         FlatPtr end_of_range = ((FlatPtr)end_of_kernel_image & ~(FlatPtr)0x1fffff) + 0x200000;
-        MUST(m_region_tree.place_specifically(*MUST(Region::create_unbacked()).leak_ptr(), VirtualRange { VirtualAddress(start_of_range), end_of_range - start_of_range }));
+        MUST(m_region_tree.with([&](auto& region_tree) { return region_tree.place_specifically(*MUST(Region::create_unbacked()).leak_ptr(), VirtualRange { VirtualAddress(start_of_range), end_of_range - start_of_range }); }));
     }
 
     // Allocate a virtual address range for our array
     // This looks awkward, but it basically creates a dummy region to occupy the address range permanently.
     auto& region = *MUST(Region::create_unbacked()).leak_ptr();
-    MUST(m_region_tree.place_anywhere(region, RandomizeVirtualAddress::No, physical_page_array_pages * PAGE_SIZE));
+    MUST(m_region_tree.with([&](auto& region_tree) { return region_tree.place_anywhere(region, RandomizeVirtualAddress::No, physical_page_array_pages * PAGE_SIZE); }));
     auto range = region.range();
 
     // Now that we have our special m_physical_pages_region region with enough pages to hold the entire array
@@ -643,7 +643,7 @@ Region* MemoryManager::kernel_region_from_vaddr(VirtualAddress address)
     if (is_user_address(address))
         return nullptr;
 
-    return MM.m_region_tree.find_region_containing(address);
+    return MM.m_region_tree.with([&](auto& region_tree) { return region_tree.find_region_containing(address); });
 }
 
 Region* MemoryManager::find_user_region_from_vaddr_no_lock(AddressSpace& space, VirtualAddress vaddr)
@@ -747,7 +747,7 @@ ErrorOr<NonnullOwnPtr<Region>> MemoryManager::allocate_contiguous_kernel_region(
         name_kstring = TRY(KString::try_create(name));
     auto vmobject = TRY(AnonymousVMObject::try_create_physically_contiguous_with_size(size));
     auto region = TRY(Region::create_unplaced(move(vmobject), 0, move(name_kstring), access, cacheable));
-    TRY(m_region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size));
+    TRY(m_region_tree.with([&](auto& region_tree) { return region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size); }));
     TRY(region->map(kernel_page_directory()));
     return region;
 }
@@ -790,7 +790,7 @@ ErrorOr<NonnullOwnPtr<Region>> MemoryManager::allocate_kernel_region(size_t size
         name_kstring = TRY(KString::try_create(name));
     auto vmobject = TRY(AnonymousVMObject::try_create_with_size(size, strategy));
     auto region = TRY(Region::create_unplaced(move(vmobject), 0, move(name_kstring), access, cacheable));
-    TRY(m_region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size));
+    TRY(m_region_tree.with([&](auto& region_tree) { return region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size); }));
     TRY(region->map(kernel_page_directory()));
     return region;
 }
@@ -803,7 +803,7 @@ ErrorOr<NonnullOwnPtr<Region>> MemoryManager::allocate_kernel_region(PhysicalAdd
     if (!name.is_null())
         name_kstring = TRY(KString::try_create(name));
     auto region = TRY(Region::create_unplaced(move(vmobject), 0, move(name_kstring), access, cacheable));
-    TRY(m_region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size, PAGE_SIZE));
+    TRY(m_region_tree.with([&](auto& region_tree) { return region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size, PAGE_SIZE); }));
     TRY(region->map(kernel_page_directory()));
     return region;
 }
@@ -817,7 +817,7 @@ ErrorOr<NonnullOwnPtr<Region>> MemoryManager::allocate_kernel_region_with_vmobje
         name_kstring = TRY(KString::try_create(name));
 
     auto region = TRY(Region::create_unplaced(vmobject, 0, move(name_kstring), access, cacheable));
-    TRY(m_region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size));
+    TRY(m_region_tree.with([&](auto& region_tree) { return region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size); }));
     TRY(region->map(kernel_page_directory()));
     return region;
 }
@@ -1120,7 +1120,7 @@ bool MemoryManager::validate_user_stack(AddressSpace& space, VirtualAddress vadd
 void MemoryManager::unregister_kernel_region(Region& region)
 {
     VERIFY(region.is_kernel());
-    m_region_tree.remove(region);
+    m_region_tree.with([&](auto& region_tree) { region_tree.remove(region); });
 }
 
 void MemoryManager::dump_kernel_regions()
@@ -1134,20 +1134,21 @@ void MemoryManager::dump_kernel_regions()
     dbgln("BEGIN{}         END{}        SIZE{}       ACCESS NAME",
         addr_padding, addr_padding, addr_padding);
     SpinlockLocker lock(s_mm_lock);
-    SpinlockLocker tree_locker(m_region_tree.get_lock());
-    for (auto const& region : m_region_tree.regions()) {
-        dbgln("{:p} -- {:p} {:p} {:c}{:c}{:c}{:c}{:c}{:c} {}",
-            region.vaddr().get(),
-            region.vaddr().offset(region.size() - 1).get(),
-            region.size(),
-            region.is_readable() ? 'R' : ' ',
-            region.is_writable() ? 'W' : ' ',
-            region.is_executable() ? 'X' : ' ',
-            region.is_shared() ? 'S' : ' ',
-            region.is_stack() ? 'T' : ' ',
-            region.is_syscall_region() ? 'C' : ' ',
-            region.name());
-    }
+    m_region_tree.with([&](auto& region_tree) {
+        for (auto& region : region_tree.regions()) {
+            dbgln("{:p} -- {:p} {:p} {:c}{:c}{:c}{:c}{:c}{:c} {}",
+                region.vaddr().get(),
+                region.vaddr().offset(region.size() - 1).get(),
+                region.size(),
+                region.is_readable() ? 'R' : ' ',
+                region.is_writable() ? 'W' : ' ',
+                region.is_executable() ? 'X' : ' ',
+                region.is_shared() ? 'S' : ' ',
+                region.is_stack() ? 'T' : ' ',
+                region.is_syscall_region() ? 'C' : ' ',
+                region.name());
+        }
+    });
 }
 
 void MemoryManager::set_page_writable_direct(VirtualAddress vaddr, bool writable)
@@ -1201,7 +1202,7 @@ ErrorOr<NonnullOwnPtr<Memory::Region>> MemoryManager::create_identity_mapped_reg
 ErrorOr<NonnullOwnPtr<Region>> MemoryManager::allocate_unbacked_region_anywhere(size_t size, size_t alignment)
 {
     auto region = TRY(Region::create_unbacked());
-    TRY(m_region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size, alignment));
+    TRY(m_region_tree.with([&](auto& region_tree) { return region_tree.place_anywhere(*region, RandomizeVirtualAddress::No, size, alignment); }));
     return region;
 }
 
diff --git a/Kernel/Memory/MemoryManager.h b/Kernel/Memory/MemoryManager.h
index 84eedc7570..6bf827773c 100644
--- a/Kernel/Memory/MemoryManager.h
+++ b/Kernel/Memory/MemoryManager.h
@@ -298,7 +298,7 @@ private:
     PhysicalPageEntry* m_physical_page_entries { nullptr };
     size_t m_physical_page_entries_count { 0 };
 
-    RegionTree m_region_tree;
+    SpinlockProtected<RegionTree> m_region_tree;
 
     Vector<UsedMemoryRange> m_used_memory_ranges;
     Vector<PhysicalMemoryRange> m_physical_memory_ranges;
diff --git a/Kernel/Memory/RegionTree.cpp b/Kernel/Memory/RegionTree.cpp
index ac2d55093d..72c43b98e8 100644
--- a/Kernel/Memory/RegionTree.cpp
+++ b/Kernel/Memory/RegionTree.cpp
@@ -151,7 +151,6 @@ ErrorOr<VirtualRange> RegionTree::allocate_range_randomized(size_t size, size_t
 
 ErrorOr<void> RegionTree::place_anywhere(Region& region, RandomizeVirtualAddress randomize_virtual_address, size_t size, size_t alignment)
 {
-    SpinlockLocker locker(m_lock);
     auto range = TRY(randomize_virtual_address == RandomizeVirtualAddress::Yes ? allocate_range_randomized(size, alignment) : allocate_range_anywhere(size, alignment));
     region.m_range = range;
     m_regions.insert(region.vaddr().get(), region);
@@ -160,7 +159,6 @@ ErrorOr<void> RegionTree::place_anywhere(Region& region, RandomizeVirtualAddress
 
 ErrorOr<void> RegionTree::place_specifically(Region& region, VirtualRange const& range)
 {
-    SpinlockLocker locker(m_lock);
     auto allocated_range = TRY(allocate_range_specific(range.base(), range.size()));
     region.m_range = allocated_range;
     m_regions.insert(region.vaddr().get(), region);
@@ -169,13 +167,11 @@ ErrorOr<void> RegionTree::place_specifically(Region& region, VirtualRange const&
 
 bool RegionTree::remove(Region& region)
 {
-    SpinlockLocker locker(m_lock);
     return m_regions.remove(region.range().base().get());
 }
 
 Region* RegionTree::find_region_containing(VirtualAddress address)
 {
-    SpinlockLocker locker(m_lock);
     auto* region = m_regions.find_largest_not_above(address.get());
     if (!region || !region->contains(address))
         return nullptr;
@@ -184,7 +180,6 @@ Region* RegionTree::find_region_containing(VirtualAddress address)
 
 Region* RegionTree::find_region_containing(VirtualRange range)
 {
-    SpinlockLocker lock(m_lock);
     auto* region = m_regions.find_largest_not_above(range.base().get());
     if (!region || !region->contains(range))
         return nullptr;
diff --git a/Kernel/PerformanceEventBuffer.cpp b/Kernel/PerformanceEventBuffer.cpp
index 11dfbd8390..4852c4c8cf 100644
--- a/Kernel/PerformanceEventBuffer.cpp
+++ b/Kernel/PerformanceEventBuffer.cpp
@@ -354,12 +354,13 @@ ErrorOr<void> PerformanceEventBuffer::add_process(Process const& process, Proces
     });
     TRY(result);
 
-    for (auto const& region : process.address_space().regions()) {
-        TRY(append_with_ip_and_bp(process.pid(), 0,
-            0, 0, PERF_EVENT_MMAP, 0, region.range().base().get(), region.range().size(), region.name()));
-    }
-
-    return {};
+    return process.address_space().region_tree().with([&](auto& region_tree) -> ErrorOr<void> {
+        for (auto const& region : region_tree.regions()) {
+            TRY(append_with_ip_and_bp(process.pid(), 0,
+                0, 0, PERF_EVENT_MMAP, 0, region.range().base().get(), region.range().size(), region.name()));
+        }
+        return {};
+    });
 }
 
 ErrorOr<FlatPtr> PerformanceEventBuffer::register_string(NonnullOwnPtr<KString> string)
diff --git a/Kernel/ProcessSpecificExposed.cpp b/Kernel/ProcessSpecificExposed.cpp
index 0e39ccb188..1bda213e5c 100644
--- a/Kernel/ProcessSpecificExposed.cpp
+++ b/Kernel/ProcessSpecificExposed.cpp
@@ -267,9 +267,8 @@ ErrorOr<void> Process::procfs_get_fds_stats(KBufferBuilder& builder) const
 ErrorOr<void> Process::procfs_get_virtual_memory_stats(KBufferBuilder& builder) const
 {
     auto array = TRY(JsonArraySerializer<>::try_create(builder));
-    {
-        SpinlockLocker lock(address_space().get_lock());
-        for (auto const& region : address_space().regions()) {
+    TRY(address_space().region_tree().with([&](auto& region_tree) -> ErrorOr<void> {
+        for (auto const& region : region_tree.regions()) {
             auto current_process_credentials = Process::current().credentials();
             if (!region.is_user() && !current_process_credentials->is_superuser())
                 continue;
@@ -306,7 +305,8 @@ ErrorOr<void> Process::procfs_get_virtual_memory_stats(KBufferBuilder& builder)
             TRY(region_object.add("pagemap"sv, pagemap_builder.string_view()));
             TRY(region_object.finish());
         }
-    }
+        return {};
+    }));
     TRY(array.finish());
     return {};
 }
diff --git a/Kernel/Syscalls/fork.cpp b/Kernel/Syscalls/fork.cpp
index b4805ff1b8..68a637d8f5 100644
--- a/Kernel/Syscalls/fork.cpp
+++ b/Kernel/Syscalls/fork.cpp
@@ -124,17 +124,21 @@ ErrorOr<FlatPtr> Process::sys$fork(RegisterState& regs)
 #endif
 
     {
-        SpinlockLocker lock(address_space().get_lock());
-        for (auto& region : address_space().regions()) {
-            dbgln_if(FORK_DEBUG, "fork: cloning Region '{}' @ {}", region.name(), region.vaddr());
-            auto region_clone = TRY(region.try_clone());
-            TRY(region_clone->map(child->address_space().page_directory(), Memory::ShouldFlushTLB::No));
-            TRY(child->address_space().region_tree().place_specifically(*region_clone, region.range()));
-            auto* child_region = region_clone.leak_ptr();
-
-            if (&region == m_master_tls_region.unsafe_ptr())
-                child->m_master_tls_region = TRY(child_region->try_make_weak_ptr());
-        }
+        TRY(address_space().region_tree().with([&](auto& parent_region_tree) -> ErrorOr<void> {
+            return child->address_space().region_tree().with([&](auto& child_region_tree) -> ErrorOr<void> {
+                for (auto& region : parent_region_tree.regions()) {
+                    dbgln_if(FORK_DEBUG, "fork: cloning Region '{}' @ {}", region.name(), region.vaddr());
+                    auto region_clone = TRY(region.try_clone());
+                    TRY(region_clone->map(child->address_space().page_directory(), Memory::ShouldFlushTLB::No));
+                    TRY(child_region_tree.place_specifically(*region_clone, region.range()));
+                    auto* child_region = region_clone.leak_ptr();
+
+                    if (&region == m_master_tls_region.unsafe_ptr())
+                        child->m_master_tls_region = TRY(child_region->try_make_weak_ptr());
+                }
+                return {};
+            });
+        }));
     }
 
     thread_finalizer_guard.disarm();
@@ -151,5 +155,4 @@ ErrorOr<FlatPtr> Process::sys$fork(RegisterState& regs)
 
     return child_pid;
 }
-
 }