Kernel: Split VMObject into two classes: Anonymous- and InodeVMObject

InodeVMObject is a VMObject with an underlying Inode in the filesystem.
AnonymousVMObject has no Inode.

I'm happy that InodeVMObject::inode() can now return Inode& instead of
VMObject::inode() return Inode*. :^)

Kernel/VM/AnonymousVMObject.cpp

@@ -0,0 +1,41 @@
+#include <Kernel/VM/AnonymousVMObject.h>
+#include <Kernel/VM/PhysicalPage.h>
+
+NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_with_size(size_t size)
+{
+    size = ceil_div(size, PAGE_SIZE) * PAGE_SIZE;
+    return adopt(*new AnonymousVMObject(size));
+}
+
+NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_for_physical_range(PhysicalAddress paddr, size_t size)
+{
+    size = ceil_div(size, PAGE_SIZE) * PAGE_SIZE;
+    return adopt(*new AnonymousVMObject(paddr, size));
+}
+
+AnonymousVMObject::AnonymousVMObject(size_t size)
+    : VMObject(size, ShouldFillPhysicalPages::Yes)
+{
+}
+
+AnonymousVMObject::AnonymousVMObject(PhysicalAddress paddr, size_t size)
+    : VMObject(size, ShouldFillPhysicalPages::No)
+{
+    for (size_t i = 0; i < size; i += PAGE_SIZE)
+        m_physical_pages.append(PhysicalPage::create(paddr.offset(i), false, false));
+    ASSERT(m_physical_pages.size() == page_count());
+}
+
+AnonymousVMObject::AnonymousVMObject(const AnonymousVMObject& other)
+    : VMObject(other)
+{
+}
+
+AnonymousVMObject::~AnonymousVMObject()
+{
+}
+
+NonnullRefPtr<VMObject> AnonymousVMObject::clone()
+{
+    return adopt(*new AnonymousVMObject(*this));
+}

Kernel/VM/AnonymousVMObject.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <Kernel/VM/PhysicalAddress.h>
+#include <Kernel/VM/VMObject.h>
+
+class AnonymousVMObject final : public VMObject {
+public:
+    virtual ~AnonymousVMObject() override;
+
+    static NonnullRefPtr<AnonymousVMObject> create_with_size(size_t);
+    static NonnullRefPtr<AnonymousVMObject> create_for_physical_range(PhysicalAddress, size_t);
+    virtual NonnullRefPtr<VMObject> clone() override;
+
+private:
+    explicit AnonymousVMObject(size_t);
+    explicit AnonymousVMObject(const AnonymousVMObject&);
+    AnonymousVMObject(PhysicalAddress, size_t);
+
+    AnonymousVMObject& operator=(const AnonymousVMObject&) = delete;
+    AnonymousVMObject& operator=(AnonymousVMObject&&) = delete;
+    AnonymousVMObject(AnonymousVMObject&&) = delete;
+
+    virtual bool is_anonymous() const override { return true; }
+};

Kernel/VM/InodeVMObject.cpp

@@ -0,0 +1,131 @@
+#include <Kernel/FileSystem/Inode.h>
+#include <Kernel/VM/InodeVMObject.h>
+#include <Kernel/VM/MemoryManager.h>
+#include <Kernel/VM/Region.h>
+
+NonnullRefPtr<InodeVMObject> InodeVMObject::create_with_inode(Inode& inode)
+{
+    InterruptDisabler disabler;
+    if (inode.vmo())
+        return *inode.vmo();
+    auto vmo = adopt(*new InodeVMObject(inode));
+    vmo->inode().set_vmo(*vmo);
+    return vmo;
+}
+
+NonnullRefPtr<VMObject> InodeVMObject::clone()
+{
+    return adopt(*new InodeVMObject(*this));
+}
+
+InodeVMObject::InodeVMObject(Inode& inode)
+    : VMObject(ceil_div(inode.size(), PAGE_SIZE) * PAGE_SIZE, ShouldFillPhysicalPages::Yes)
+    , m_inode(inode)
+{
+}
+
+InodeVMObject::InodeVMObject(const InodeVMObject& other)
+    : VMObject(other)
+    , m_inode(other.m_inode)
+{
+}
+
+InodeVMObject::~InodeVMObject()
+{
+    ASSERT(inode().vmo() == this);
+}
+
+void InodeVMObject::inode_size_changed(Badge<Inode>, size_t old_size, size_t new_size)
+{
+    dbgprintf("VMObject::inode_size_changed: {%u:%u} %u -> %u\n",
+        m_inode->fsid(), m_inode->index(),
+        old_size, new_size);
+
+    InterruptDisabler disabler;
+
+    auto old_page_count = page_count();
+    m_size = new_size;
+
+    if (page_count() > old_page_count) {
+        // Add null pages and let the fault handler page these in when that day comes.
+        for (auto i = old_page_count; i < page_count(); ++i)
+            m_physical_pages.append(nullptr);
+    } else {
+        // Prune the no-longer valid pages. I'm not sure this is actually correct behavior.
+        for (auto i = page_count(); i < old_page_count; ++i)
+            m_physical_pages.take_last();
+    }
+
+    // FIXME: Consolidate with inode_contents_changed() so we only do a single walk.
+    for_each_region([](Region& region) {
+        ASSERT(region.page_directory());
+        MM.remap_region(*region.page_directory(), region);
+    });
+}
+
+void InodeVMObject::inode_contents_changed(Badge<Inode>, off_t offset, ssize_t size, const u8* data)
+{
+    (void)size;
+    (void)data;
+    InterruptDisabler disabler;
+    ASSERT(offset >= 0);
+
+    // FIXME: Only invalidate the parts that actually changed.
+    for (auto& physical_page : m_physical_pages)
+        physical_page = nullptr;
+
+#if 0
+    size_t current_offset = offset;
+    size_t remaining_bytes = size;
+    const u8* data_ptr = data;
+
+    auto to_page_index = [] (size_t offset) -> size_t {
+        return offset / PAGE_SIZE;
+    };
+
+    if (current_offset & PAGE_MASK) {
+        size_t page_index = to_page_index(current_offset);
+        size_t bytes_to_copy = min(size, PAGE_SIZE - (current_offset & PAGE_MASK));
+        if (m_physical_pages[page_index]) {
+            auto* ptr = MM.quickmap_page(*m_physical_pages[page_index]);
+            memcpy(ptr, data_ptr, bytes_to_copy);
+            MM.unquickmap_page();
+        }
+        current_offset += bytes_to_copy;
+        data += bytes_to_copy;
+        remaining_bytes -= bytes_to_copy;
+    }
+
+    for (size_t page_index = to_page_index(current_offset); page_index < m_physical_pages.size(); ++page_index) {
+        size_t bytes_to_copy = PAGE_SIZE - (current_offset & PAGE_MASK);
+        if (m_physical_pages[page_index]) {
+            auto* ptr = MM.quickmap_page(*m_physical_pages[page_index]);
+            memcpy(ptr, data_ptr, bytes_to_copy);
+            MM.unquickmap_page();
+        }
+        current_offset += bytes_to_copy;
+        data += bytes_to_copy;
+    }
+#endif
+
+    // FIXME: Consolidate with inode_size_changed() so we only do a single walk.
+    for_each_region([](Region& region) {
+        ASSERT(region.page_directory());
+        MM.remap_region(*region.page_directory(), region);
+    });
+}
+
+template<typename Callback>
+void VMObject::for_each_region(Callback callback)
+{
+    // FIXME: Figure out a better data structure so we don't have to walk every single region every time an inode changes.
+    //        Perhaps VMObject could have a Vector<Region*> with all of his mappers?
+    for (auto* region : MM.m_user_regions) {
+        if (&region->vmo() == this)
+            callback(*region);
+    }
+    for (auto* region : MM.m_kernel_regions) {
+        if (&region->vmo() == this)
+            callback(*region);
+    }
+}

Kernel/VM/InodeVMObject.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <Kernel/UnixTypes.h>
+#include <Kernel/VM/VMObject.h>
+
+class InodeVMObject final : public VMObject {
+public:
+    virtual ~InodeVMObject() override;
+
+    static NonnullRefPtr<InodeVMObject> create_with_inode(Inode&);
+    virtual NonnullRefPtr<VMObject> clone() override;
+
+    Inode& inode() { return *m_inode; }
+    const Inode& inode() const { return *m_inode; }
+
+    void inode_contents_changed(Badge<Inode>, off_t, ssize_t, const u8*);
+    void inode_size_changed(Badge<Inode>, size_t old_size, size_t new_size);
+
+private:
+    explicit InodeVMObject(Inode&);
+    explicit InodeVMObject(const InodeVMObject&);
+
+    InodeVMObject& operator=(const InodeVMObject&) = delete;
+    InodeVMObject& operator=(InodeVMObject&&) = delete;
+    InodeVMObject(InodeVMObject&&) = delete;
+
+    virtual bool is_inode() const override { return true; }
+
+    NonnullRefPtr<Inode> m_inode;
+};

Kernel/VM/MemoryManager.cpp

@@ -6,6 +6,8 @@
 #include <Kernel/Arch/i386/CPU.h>
 #include <Kernel/FileSystem/Inode.h>
 #include <Kernel/Multiboot.h>
+#include <Kernel/VM/AnonymousVMObject.h>
+#include <Kernel/VM/InodeVMObject.h>
 #include <Kernel/VM/MemoryManager.h>
 
 //#define MM_DEBUG
@@ -352,10 +354,11 @@ bool MemoryManager::page_in_from_inode(Region& region, unsigned page_index_in_re
 {
     ASSERT(region.page_directory());
     auto& vmo = region.vmo();
-    ASSERT(!vmo.is_anonymous());
-    ASSERT(vmo.inode());
+    ASSERT(vmo.is_inode());
 
-    auto& vmo_page = vmo.physical_pages()[region.first_page_index() + page_index_in_region];
+    auto& inode_vmobject = static_cast<InodeVMObject&>(vmo);
+
+    auto& vmo_page = inode_vmobject.physical_pages()[region.first_page_index() + page_index_in_region];
 
     InterruptFlagSaver saver;
 
@@ -374,8 +377,8 @@ bool MemoryManager::page_in_from_inode(Region& region, unsigned page_index_in_re
 #endif
     sti();
     u8 page_buffer[PAGE_SIZE];
-    auto& inode = *vmo.inode();
-    auto nread = inode.read_bytes(vmo.inode_offset() + ((region.first_page_index() + page_index_in_region) * PAGE_SIZE), PAGE_SIZE, page_buffer, nullptr);
+    auto& inode = inode_vmobject.inode();
+    auto nread = inode.read_bytes((region.first_page_index() + page_index_in_region) * PAGE_SIZE, PAGE_SIZE, page_buffer, nullptr);
     if (nread < 0) {
         kprintf("MM: page_in_from_inode had error (%d) while reading!\n", nread);
         return false;
@@ -435,7 +438,7 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
     }
     auto page_index_in_region = region->page_index_from_address(fault.vaddr());
     if (fault.type() == PageFault::Type::PageNotPresent) {
-        if (region->vmo().inode()) {
+        if (region->vmo().is_inode()) {
 #ifdef PAGE_FAULT_DEBUG
             dbgprintf("NP(inode) fault in Region{%p}[%u]\n", region, page_index_in_region);
 #endif

Kernel/VM/Region.cpp

@@ -1,13 +1,14 @@
 #include <Kernel/FileSystem/Inode.h>
 #include <Kernel/Process.h>
 #include <Kernel/Thread.h>
+#include <Kernel/VM/AnonymousVMObject.h>
+#include <Kernel/VM/InodeVMObject.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/Region.h>
-#include <Kernel/VM/VMObject.h>
 
 Region::Region(const Range& range, const String& name, u8 access, bool cow)
     : m_range(range)
-    , m_vmo(VMObject::create_anonymous(size()))
+    , m_vmo(AnonymousVMObject::create_with_size(size()))
     , m_name(name)
     , m_access(access)
     , m_cow_map(Bitmap::create(m_vmo->page_count(), cow))
@@ -17,7 +18,7 @@ Region::Region(const Range& range, const String& name, u8 access, bool cow)
 
 Region::Region(const Range& range, RefPtr<Inode>&& inode, const String& name, u8 access, bool cow)
     : m_range(range)
-    , m_vmo(VMObject::create_file_backed(move(inode)))
+    , m_vmo(InodeVMObject::create_with_inode(*inode))
     , m_name(name)
     , m_access(access)
     , m_cow_map(Bitmap::create(m_vmo->page_count(), cow))
@@ -48,8 +49,7 @@ Region::~Region()
 bool Region::page_in()
 {
     ASSERT(m_page_directory);
-    ASSERT(!vmo().is_anonymous());
-    ASSERT(vmo().inode());
+    ASSERT(vmo().is_inode());
 #ifdef MM_DEBUG
     dbgprintf("MM: page_in %u pages\n", page_count());
 #endif

Kernel/VM/VMObject.cpp

@@ -3,166 +3,22 @@
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/VMObject.h>
 
-NonnullRefPtr<VMObject> VMObject::create_file_backed(RefPtr<Inode>&& inode)
-{
-    InterruptDisabler disabler;
-    if (inode->vmo())
-        return *inode->vmo();
-    auto vmo = adopt(*new VMObject(move(inode)));
-    vmo->inode()->set_vmo(*vmo);
-    return vmo;
-}
-
-NonnullRefPtr<VMObject> VMObject::create_anonymous(size_t size)
-{
-    size = ceil_div(size, PAGE_SIZE) * PAGE_SIZE;
-    return adopt(*new VMObject(size));
-}
-
-NonnullRefPtr<VMObject> VMObject::create_for_physical_range(PhysicalAddress paddr, size_t size)
-{
-    size = ceil_div(size, PAGE_SIZE) * PAGE_SIZE;
-    return adopt(*new VMObject(paddr, size));
-}
-
-NonnullRefPtr<VMObject> VMObject::clone()
-{
-    return adopt(*new VMObject(*this));
-}
-
-VMObject::VMObject(VMObject& other)
-    : m_inode_offset(other.m_inode_offset)
-    , m_size(other.m_size)
-    , m_inode(other.m_inode)
+VMObject::VMObject(const VMObject& other)
+    : m_size(other.m_size)
     , m_physical_pages(other.m_physical_pages)
 {
     MM.register_vmo(*this);
 }
 
-VMObject::VMObject(size_t size)
+VMObject::VMObject(size_t size, ShouldFillPhysicalPages should_fill_physical_pages)
     : m_size(size)
 {
     MM.register_vmo(*this);
-    m_physical_pages.resize(page_count());
-}
-
-VMObject::VMObject(PhysicalAddress paddr, size_t size)
-    : m_size(size)
-{
-    MM.register_vmo(*this);
-    for (size_t i = 0; i < size; i += PAGE_SIZE) {
-        m_physical_pages.append(PhysicalPage::create(paddr.offset(i), false, false));
-    }
-    ASSERT(m_physical_pages.size() == page_count());
-}
-
-VMObject::VMObject(RefPtr<Inode>&& inode)
-    : m_inode(move(inode))
-{
-    ASSERT(m_inode);
-    m_size = ceil_div(m_inode->size(), PAGE_SIZE) * PAGE_SIZE;
-    m_physical_pages.resize(page_count());
-    MM.register_vmo(*this);
+    if (should_fill_physical_pages == ShouldFillPhysicalPages::Yes)
+        m_physical_pages.resize(page_count());
 }
 
 VMObject::~VMObject()
 {
-    if (m_inode)
-        ASSERT(m_inode->vmo() == this);
     MM.unregister_vmo(*this);
 }
-
-template<typename Callback>
-void VMObject::for_each_region(Callback callback)
-{
-    // FIXME: Figure out a better data structure so we don't have to walk every single region every time an inode changes.
-    //        Perhaps VMObject could have a Vector<Region*> with all of his mappers?
-    for (auto* region : MM.m_user_regions) {
-        if (&region->vmo() == this)
-            callback(*region);
-    }
-    for (auto* region : MM.m_kernel_regions) {
-        if (&region->vmo() == this)
-            callback(*region);
-    }
-}
-
-void VMObject::inode_size_changed(Badge<Inode>, size_t old_size, size_t new_size)
-{
-    dbgprintf("VMObject::inode_size_changed: {%u:%u} %u -> %u\n",
-        m_inode->fsid(), m_inode->index(),
-        old_size, new_size);
-
-    InterruptDisabler disabler;
-
-    auto old_page_count = page_count();
-    m_size = new_size;
-
-    if (page_count() > old_page_count) {
-        // Add null pages and let the fault handler page these in when that day comes.
-        for (auto i = old_page_count; i < page_count(); ++i)
-            m_physical_pages.append(nullptr);
-    } else {
-        // Prune the no-longer valid pages. I'm not sure this is actually correct behavior.
-        for (auto i = page_count(); i < old_page_count; ++i)
-            m_physical_pages.take_last();
-    }
-
-    // FIXME: Consolidate with inode_contents_changed() so we only do a single walk.
-    for_each_region([](Region& region) {
-        ASSERT(region.page_directory());
-        MM.remap_region(*region.page_directory(), region);
-    });
-}
-
-void VMObject::inode_contents_changed(Badge<Inode>, off_t offset, ssize_t size, const u8* data)
-{
-    (void)size;
-    (void)data;
-    InterruptDisabler disabler;
-    ASSERT(offset >= 0);
-
-    // FIXME: Only invalidate the parts that actually changed.
-    for (auto& physical_page : m_physical_pages)
-        physical_page = nullptr;
-
-#if 0
-    size_t current_offset = offset;
-    size_t remaining_bytes = size;
-    const u8* data_ptr = data;
-
-    auto to_page_index = [] (size_t offset) -> size_t {
-        return offset / PAGE_SIZE;
-    };
-
-    if (current_offset & PAGE_MASK) {
-        size_t page_index = to_page_index(current_offset);
-        size_t bytes_to_copy = min(size, PAGE_SIZE - (current_offset & PAGE_MASK));
-        if (m_physical_pages[page_index]) {
-            auto* ptr = MM.quickmap_page(*m_physical_pages[page_index]);
-            memcpy(ptr, data_ptr, bytes_to_copy);
-            MM.unquickmap_page();
-        }
-        current_offset += bytes_to_copy;
-        data += bytes_to_copy;
-        remaining_bytes -= bytes_to_copy;
-    }
-
-    for (size_t page_index = to_page_index(current_offset); page_index < m_physical_pages.size(); ++page_index) {
-        size_t bytes_to_copy = PAGE_SIZE - (current_offset & PAGE_MASK);
-        if (m_physical_pages[page_index]) {
-            auto* ptr = MM.quickmap_page(*m_physical_pages[page_index]);
-            memcpy(ptr, data_ptr, bytes_to_copy);
-            MM.unquickmap_page();
-        }
-        current_offset += bytes_to_copy;
-        data += bytes_to_copy;
-    }
-#endif
-
-    // FIXME: Consolidate with inode_size_changed() so we only do a single walk.
-    for_each_region([](Region& region) {
-        ASSERT(region.page_directory());
-        MM.remap_region(*region.page_directory(), region);
-    });
-}

Kernel/VM/VMObject.h

@@ -1,14 +1,10 @@
 #pragma once
 
-#include <AK/AKString.h>
-#include <AK/Badge.h>
-#include <AK/RefPtr.h>
 #include <AK/RefCounted.h>
+#include <AK/RefPtr.h>
 #include <AK/Vector.h>
 #include <AK/Weakable.h>
 #include <Kernel/Lock.h>
-#include <Kernel/UnixTypes.h>
-#include <Kernel/VM/PhysicalAddress.h>
 
 class Inode;
 class PhysicalPage;
@@ -18,39 +14,37 @@ class VMObject : public RefCounted<VMObject>
     friend class MemoryManager;
 
 public:
-    static NonnullRefPtr<VMObject> create_file_backed(RefPtr<Inode>&&);
-    static NonnullRefPtr<VMObject> create_anonymous(size_t);
-    static NonnullRefPtr<VMObject> create_for_physical_range(PhysicalAddress, size_t);
-    NonnullRefPtr<VMObject> clone();
+    virtual ~VMObject();
 
-    ~VMObject();
-    bool is_anonymous() const { return !m_inode; }
+    virtual NonnullRefPtr<VMObject> clone() = 0;
 
-    Inode* inode() { return m_inode.ptr(); }
-    const Inode* inode() const { return m_inode.ptr(); }
-    size_t inode_offset() const { return m_inode_offset; }
+    virtual bool is_anonymous() const { return false; }
+    virtual bool is_inode() const { return false; }
 
     int page_count() const { return m_size / PAGE_SIZE; }
     const Vector<RefPtr<PhysicalPage>>& physical_pages() const { return m_physical_pages; }
     Vector<RefPtr<PhysicalPage>>& physical_pages() { return m_physical_pages; }
 
-    void inode_contents_changed(Badge<Inode>, off_t, ssize_t, const u8*);
-    void inode_size_changed(Badge<Inode>, size_t old_size, size_t new_size);
-
     size_t size() const { return m_size; }
 
-private:
-    VMObject(RefPtr<Inode>&&);
-    explicit VMObject(VMObject&);
-    explicit VMObject(size_t);
-    VMObject(PhysicalAddress, size_t);
+protected:
+    enum ShouldFillPhysicalPages {
+        No = 0,
+        Yes
+    };
+    VMObject(size_t, ShouldFillPhysicalPages);
+    explicit VMObject(const VMObject&);
 
     template<typename Callback>
     void for_each_region(Callback);
 
-    off_t m_inode_offset { 0 };
     size_t m_size { 0 };
-    RefPtr<Inode> m_inode;
     Vector<RefPtr<PhysicalPage>> m_physical_pages;
+
+private:
+    VMObject& operator=(const VMObject&) = delete;
+    VMObject& operator=(VMObject&&) = delete;
+    VMObject(VMObject&&) = delete;
+
     Lock m_paging_lock { "VMObject" };
 };