FileSystem: Merge symlink following logic into path resolution.

When encountering a symlink, we abandon the custody chain we've been working
on and start over with a new one (by recursing into a new resolution call.)
Caching symlinks in the custody model would be incredibly difficult to get
right with all the extra invalidation it would require, so let's just not.

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -545,18 +545,6 @@ KResult VFS::rmdir(StringView path, Custody& base)
  return parent_inode.remove_child(FileSystemPath(path).basename());
 }
 
-KResultOr<Retained<Custody>> VFS::resolve_symbolic_link(Custody& base, Inode& symlink_inode)
-{
- auto symlink_contents = symlink_inode.read_entire();
- if (!symlink_contents)
- return KResult(-ENOENT);
- auto linkee = StringView(symlink_contents.pointer(), symlink_contents.size());
-#ifdef VFS_DEBUG
- kprintf("linkee (%s)(%u) from %u:%u\n", linkee.characters(), linkee.length(), base.fsid(), base.index());
-#endif
- return resolve_path_to_custody(linkee, base);
-}
-
 RetainPtr<Inode> VFS::get_inode(InodeIdentifier inode_id)
 {
  if (!inode_id.is_valid())
@@ -659,6 +647,7 @@ KResultOr<Retained<Custody>> VFS::resolve_path_to_custody(StringView path, Custo
  return KResult(-ENOTDIR);
  if (!metadata.may_execute(current->process()))
  return KResult(-EACCES);
+ auto current_parent = custody_chain.last();
  crumb_id = crumb_inode->lookup(part);
  if (!crumb_id.is_valid())
  return KResult(-ENOENT);
@@ -672,7 +661,9 @@ KResultOr<Retained<Custody>> VFS::resolve_path_to_custody(StringView path, Custo
  }
  crumb_inode = get_inode(crumb_id);
  ASSERT(crumb_inode);
+
  custody_chain.append(Custody::create(custody_chain.last().ptr(), part, *crumb_inode));
+
  metadata = crumb_inode->metadata();
  if (metadata.is_directory()) {
  if (i != parts.size() - 1) {
@@ -687,10 +678,18 @@ KResultOr<Retained<Custody>> VFS::resolve_path_to_custody(StringView path, Custo
  if (options & O__NOERROR)
  return custody_chain.last();
  }
- auto result = resolve_symbolic_link(*custody_chain.last(), *crumb_inode);
- if (result.is_error())
+ auto symlink_contents = crumb_inode->read_entire();
+ if (!symlink_contents)
  return KResult(-ENOENT);
- crumb_id = result.value()->inode().identifier();
+
+ // FIXME: We should limit the recursion here and return -ELOOP if it goes to deep.
+ return resolve_path_to_custody(
+ StringView(symlink_contents.pointer(),
+ symlink_contents.size()),
+ *current_parent,
+ parent_custody,
+ options
+ );
  }
  }
  return custody_chain.last();

Kernel/FileSystem/VirtualFileSystem.h

@@ -108,7 +108,6 @@ class VFS {
  bool is_vfs_root(InodeIdentifier) const;
 
  void traverse_directory_inode(Inode&, Function<bool(const FS::DirectoryEntry&)>);
- KResultOr<Retained<Custody>> resolve_symbolic_link(Custody& base, Inode& symlink_inode);
 
  Mount* find_mount_for_host(InodeIdentifier);
  Mount* find_mount_for_guest(InodeIdentifier);