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/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);
+    }
+}