Kernel/Ext2FS: Don't hog both locks in Ext2FSInode::lookup()

This function was acquiring both the inode and file system locks (in
that order) which could lead to deadlocks.

Kernel/FileSystem/Ext2FileSystem.cpp

@@ -1623,12 +1623,18 @@ RefPtr<Inode> Ext2FSInode::lookup(StringView name)
  dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]:lookup(): Looking up '{}'", identifier(), name);
  if (populate_lookup_cache().is_error())
  return {};
- Locker locker(m_lock);
- auto it = m_lookup_cache.find(name.hash(), [&](auto& entry) { return entry.key == name; });
- if (it != m_lookup_cache.end())
- return fs().get_inode({ fsid(), (*it).value });
- dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]:lookup(): '{}' not found", identifier(), name);
- return {};
+
+ InodeIndex inode_index;
+ {
+ Locker locker(m_lock);
+ auto it = m_lookup_cache.find(name.hash(), [&](auto& entry) { return entry.key == name; });
+ if (it == m_lookup_cache.end()) {
+ dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]:lookup(): '{}' not found", identifier(), name);
+ return {};
+ }
+ inode_index = it->value;
+ }
+ return fs().get_inode({ fsid(), inode_index });
 }
 
 void Ext2FSInode::one_ref_left()