feat(ext4): mkdir and nested directory support

crates/servers/storage-server/src/fs/ext4/mod.rs

@@ -586,5 +586,60 @@ impl<B: BlockDevice> FileSystem for Ext4<B> {
         self.open_files[handle.raw() as usize].as_ref().map(|f| f.size)
     }
 
-    fn mkdir(&mut self, _path: &[u8]) -> bool { false }
+    fn mkdir(&mut self, path: &[u8]) -> bool {
+        let (parent_inode_num, dirname) = match self.resolve_parent(path) {
+            Some(v) => v,
+            None => return false,
+        };
+        let parent_inode = match self.read_inode(parent_inode_num) {
+            Some(i) => i,
+            None => return false,
+        };
+        if !parent_inode.is_dir() { return false; }
+
+        if dir::find_entry(&mut self.device, &self.sb, self.gdt_block, &parent_inode, dirname).is_some() {
+            return false;
+        }
+
+        let new_inode_num = match self.alloc_inode() {
+            Some(n) => n,
+            None => return false,
+        };
+        let new_block = match self.alloc_block() {
+            Some(b) => b,
+            None => { self.free_inode(new_inode_num); return false; }
+        };
+
+        let mut new_inode = Self::init_empty_inode(0x4000 | 0o755);
+        new_inode.links_count = 2;
+        new_inode.size = self.sb.block_size as u64;
+        new_inode.blocks_count = (self.sb.block_size / 512) as u32;
+        if !Self::append_extent(&mut new_inode.block_data, 0, new_block as u64, 1) {
+            self.free_block(new_block);
+            self.free_inode(new_inode_num);
+            return false;
+        }
+        self.write_inode(new_inode_num, &new_inode);
+
+        let mut dir_block = [0u8; 4096];
+        dir::init_dir_block(&mut dir_block, new_inode_num, parent_inode_num, self.sb.block_size);
+        io::write_block(&mut self.device, new_block as u64, self.sb.sectors_per_block(), &dir_block);
+
+        let parent_inode = match self.read_inode(parent_inode_num) {
+            Some(i) => i,
+            None => return false,
+        };
+        if !dir::add_entry(&mut self.device, &self.sb, self.gdt_block, &parent_inode, dirname, new_inode_num, 2) {
+            self.free_block(new_block);
+            self.free_inode(new_inode_num);
+            return false;
+        }
+
+        if let Some(mut pi) = self.read_inode(parent_inode_num) {
+            pi.links_count += 1;
+            self.write_inode(parent_inode_num, &pi);
+        }
+
+        true
+    }
 }