Generalize the SpinLock and move it to AK.

Add a separate lock to protect the VFS. I think this might be a good idea.
I'm not sure it's a good approach though. I'll fiddle with it as I go along.

It's really fun to figure out all these things on my own.

VirtualFileSystem/FileHandle.cpp

@@ -24,6 +24,8 @@ bool additionWouldOverflow(Unix::off_t a, Unix::off_t b)
 
 int FileHandle::stat(Unix::stat* buffer)
 {
+    Locker locker(VirtualFileSystem::lock());
+
     if (!m_vnode)
         return -EBADF;
 
@@ -49,6 +51,8 @@ int FileHandle::stat(Unix::stat* buffer)
 
 Unix::off_t FileHandle::seek(Unix::off_t offset, int whence)
 {
+    Locker locker(VirtualFileSystem::lock());
+
     if (!m_vnode)
         return -EBADF;
 
@@ -91,6 +95,8 @@ Unix::off_t FileHandle::seek(Unix::off_t offset, int whence)
 
 Unix::ssize_t FileHandle::read(byte* buffer, Unix::size_t count)
 {
+    Locker locker(VirtualFileSystem::lock());
+
     if (m_vnode->isCharacterDevice()) {
         // FIXME: What should happen to m_currentOffset?
         return m_vnode->characterDevice()->read(buffer, count);
@@ -102,6 +108,8 @@ Unix::ssize_t FileHandle::read(byte* buffer, Unix::size_t count)
 
 ByteBuffer FileHandle::readEntireFile()
 {
+    Locker locker(VirtualFileSystem::lock());
+
     if (m_vnode->isCharacterDevice()) {
         auto buffer = ByteBuffer::createUninitialized(1024);
         Unix::ssize_t nread = m_vnode->characterDevice()->read(buffer.pointer(), buffer.size());

VirtualFileSystem/VirtualFileSystem.cpp

@@ -20,9 +20,18 @@ VirtualFileSystem& VirtualFileSystem::the()
     return *s_the;
 }
 
+static SpinLock* s_vfsLock;
+
+SpinLock& VirtualFileSystem::lock()
+{
+    ASSERT(s_vfsLock);
+    return *s_vfsLock;
+}
+
 void VirtualFileSystem::initializeGlobals()
 {
     s_the = nullptr;
+    s_vfsLock = new SpinLock;
     FileSystem::initializeGlobals();
 }
 
@@ -336,6 +345,8 @@ void VirtualFileSystem::listDirectoryRecursively(const String& path)
 
 bool VirtualFileSystem::touch(const String& path)
 {
+    Locker locker(VirtualFileSystem::lock());
+
     auto inode = resolvePath(path);
     if (!inode.isValid())
         return false;
@@ -344,6 +355,8 @@ bool VirtualFileSystem::touch(const String& path)
 
 OwnPtr<FileHandle> VirtualFileSystem::open(const String& path)
 {
+    Locker locker(VirtualFileSystem::lock());
+
     auto inode = resolvePath(path);
     if (!inode.isValid())
         return nullptr;
@@ -355,6 +368,8 @@ OwnPtr<FileHandle> VirtualFileSystem::open(const String& path)
 
 OwnPtr<FileHandle> VirtualFileSystem::create(const String& path)
 {
+    Locker locker(VirtualFileSystem::lock());
+
     // FIXME: Do the real thing, not just this fake thing!
     (void) path;
     m_rootNode->fileSystem()->createInode(m_rootNode->fileSystem()->rootInode(), "empty", 0100644, 0);
@@ -363,6 +378,8 @@ OwnPtr<FileHandle> VirtualFileSystem::create(const String& path)
 
 OwnPtr<FileHandle> VirtualFileSystem::mkdir(const String& path)
 {
+    Locker locker(VirtualFileSystem::lock());
+
     // FIXME: Do the real thing, not just this fake thing!
     (void) path;
     m_rootNode->fileSystem()->makeDirectory(m_rootNode->fileSystem()->rootInode(), "mydir", 0400755);

VirtualFileSystem/VirtualFileSystem.h

@@ -5,6 +5,7 @@
 #include <AK/RetainPtr.h>
 #include <AK/String.h>
 #include <AK/Vector.h>
+#include <AK/Lock.h>
 #include "InodeIdentifier.h"
 #include "Limits.h"
 
@@ -15,6 +16,7 @@ class FileSystem;
 class VirtualFileSystem {
 public:
     static void initializeGlobals();
+    static SpinLock& lock();
 
     struct Node {
         InodeIdentifier inode;

VirtualFileSystem/test.cpp

@@ -21,6 +21,8 @@ int main(int c, char** v)
     if (c >= 2)
         filename = v[1];
 
+    VirtualFileSystem::initializeGlobals();
+
     VirtualFileSystem vfs;
 
     auto zero = make<ZeroDevice>();