feat(ext4): file create, write, and delete with extent management

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

@@ -296,6 +296,63 @@ impl<B: BlockDevice> Ext4<B> {
         }
         None
     }
+
+    fn resolve_parent<'a>(&mut self, path: &'a [u8]) -> Option<(u32, &'a [u8])> {
+        let path = if path.starts_with(b"/") { &path[1..] } else { path };
+        if let Some(last_slash) = path.iter().rposition(|&b| b == b'/') {
+            let parent_path = &path[..last_slash];
+            let filename = &path[last_slash + 1..];
+            let parent_inode = self.resolve_path(parent_path)?;
+            Some((parent_inode, filename))
+        } else {
+            Some((ROOT_INODE, path))
+        }
+    }
+
+    fn append_extent(block_data: &mut [u8], logical_block: u32, physical_block: u64, length: u16) -> bool {
+        let magic = read_u16(block_data, 0);
+        if magic != EXTENT_MAGIC { return false; }
+        let entries = read_u16(block_data, 2);
+        let max = read_u16(block_data, 4);
+
+        if entries > 0 {
+            let last_off = 12 + (entries as usize - 1) * 12;
+            let last = Extent::parse(&block_data[last_off..last_off + 12]);
+            if last.physical_block + last.length as u64 == physical_block
+                && last.logical_block + last.length as u32 == logical_block
+            {
+                let new_len = last.length + length;
+                io::write_u16(block_data, last_off + 4, new_len);
+                return true;
+            }
+        }
+
+        if entries >= max { return false; }
+        let off = 12 + entries as usize * 12;
+        if off + 12 > block_data.len() { return false; }
+        io::write_u32(block_data, off, logical_block);
+        io::write_u16(block_data, off + 4, length);
+        io::write_u16(block_data, off + 6, (physical_block >> 32) as u16);
+        io::write_u32(block_data, off + 8, physical_block as u32);
+        io::write_u16(block_data, 2, entries + 1);
+        true
+    }
+
+    fn free_all_blocks(&mut self, inode: &Inode) {
+        if !inode.uses_extents() { return; }
+        let hdr = &inode.block_data;
+        let magic = read_u16(hdr, 0);
+        if magic != EXTENT_MAGIC { return; }
+        let entries = read_u16(hdr, 2);
+        for i in 0..entries as usize {
+            let off = 12 + i * 12;
+            if off + 12 > hdr.len() { break; }
+            let ext = Extent::parse(&hdr[off..off + 12]);
+            for b in 0..ext.length as u32 {
+                self.free_block(ext.physical_block as u32 + b);
+            }
+        }
+    }
 }
 
 impl<B: BlockDevice> FileSystem for Ext4<B> {
@@ -347,12 +404,76 @@ impl<B: BlockDevice> FileSystem for Ext4<B> {
         Some(chunk)
     }
 
-    fn write(&mut self, _handle: FileHandle, _buf: &[u8]) -> Option<usize> {
-        None
+    fn write(&mut self, handle: FileHandle, buf: &[u8]) -> Option<usize> {
+        let file = *self.open_files[handle.raw() as usize].as_ref()?;
+        let bs = self.sb.block_size;
+        let mut written = 0;
+        let mut offset = file.offset;
+        let mut block_data = file.block_data;
+        let mut size = file.size;
+        let inode_num = file.inode_num;
+
+        while written < buf.len() {
+            let logical_block = (offset / bs) as u32;
+            let byte_in_block = offset % bs;
+
+            let tmp_inode = Inode {
+                mode: 0, size: size as u64, flags: 0x80000,
+                links_count: 0, blocks_count: 0, block_data,
+            };
+            let phys_block = match self.map_logical_block(&tmp_inode, logical_block) {
+                Some(p) => p,
+                None => {
+                    let new_block = self.alloc_block()?;
+                    if !Self::append_extent(&mut block_data, logical_block, new_block as u64, 1) {
+                        self.free_block(new_block);
+                        break;
+                    }
+                    new_block as u64
+                }
+            };
+
+            let mut block_buf = [0u8; 4096];
+            if byte_in_block > 0 || (buf.len() - written) < bs {
+                read_block(&mut self.device, phys_block, self.sb.sectors_per_block(), &mut block_buf);
+            }
+
+            let available = bs - byte_in_block;
+            let chunk = available.min(buf.len() - written);
+            block_buf[byte_in_block..byte_in_block + chunk].copy_from_slice(&buf[written..written + chunk]);
+            io::write_block(&mut self.device, phys_block, self.sb.sectors_per_block(), &block_buf);
+
+            written += chunk;
+            offset += chunk;
+            if offset > size { size = offset; }
+        }
+
+        if written > 0 {
+            if let Some(f) = self.open_files[handle.raw() as usize].as_mut() {
+                f.offset = offset;
+                f.size = size;
+                f.block_data = block_data;
+            }
+            let mut inode = match self.read_inode(inode_num) {
+                Some(i) => i,
+                None => return Some(written),
+            };
+            inode.size = size as u64;
+            inode.block_data = block_data;
+            self.write_inode(inode_num, &inode);
+        }
+
+        Some(written)
     }
 
     fn close(&mut self, handle: FileHandle) {
-        self.open_files[handle.raw() as usize] = None;
+        if let Some(file) = self.open_files[handle.raw() as usize].take() {
+            if let Some(mut inode) = self.read_inode(file.inode_num) {
+                inode.size = file.size as u64;
+                inode.block_data = file.block_data;
+                self.write_inode(file.inode_num, &inode);
+            }
+        }
     }
 
     fn list_dir(&mut self, path: &[u8], entries: &mut [DirEntry]) -> Option<usize> {
@@ -407,12 +528,58 @@ impl<B: BlockDevice> FileSystem for Ext4<B> {
         Some(count)
     }
 
-    fn create(&mut self, _path: &[u8]) -> Option<FileHandle> {
-        None
+    fn create(&mut self, path: &[u8]) -> Option<FileHandle> {
+        let (parent_inode_num, filename) = self.resolve_parent(path)?;
+        let parent_inode = self.read_inode(parent_inode_num)?;
+        if !parent_inode.is_dir() { return None; }
+
+        if dir::find_entry(&mut self.device, &self.sb, self.gdt_block, &parent_inode, filename).is_some() {
+            return None;
         }
 
-    fn delete(&mut self, _path: &[u8]) -> bool {
-        false
+        let new_inode_num = self.alloc_inode()?;
+        let new_inode = Self::init_empty_inode(0x8000 | 0o644);
+        self.write_inode(new_inode_num, &new_inode);
+
+        let parent_inode = self.read_inode(parent_inode_num)?;
+        if !dir::add_entry(&mut self.device, &self.sb, self.gdt_block, &parent_inode, filename, new_inode_num, 1) {
+            self.free_inode(new_inode_num);
+            return None;
+        }
+
+        let handle = self.alloc_handle()?;
+        self.open_files[handle.raw() as usize] = Some(OpenFile {
+            inode_num: new_inode_num,
+            size: 0,
+            offset: 0,
+            name: FileName::from_bytes(path),
+            block_data: new_inode.block_data,
+        });
+        Some(handle)
+    }
+
+    fn delete(&mut self, path: &[u8]) -> bool {
+        let (parent_inode_num, filename) = 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,
+        };
+
+        let child_inode_num = match dir::remove_entry(
+            &mut self.device, &self.sb, self.gdt_block, &parent_inode, filename,
+        ) {
+            Some(n) => n,
+            None => return false,
+        };
+
+        if let Some(child_inode) = self.read_inode(child_inode_num) {
+            self.free_all_blocks(&child_inode);
+        }
+        self.free_inode(child_inode_num);
+        true
     }
 
     fn file_size(&mut self, handle: FileHandle) -> Option<usize> {

crates/servers/storage-server/src/tests/ext4.rs

@@ -368,6 +368,51 @@ fn list_dir_after_add() {
     assert_eq!(count, 2);
 }
 
+#[test]
+fn create_file_and_read_back() {
+    let mut fs = Ext4::mount(format_ext4_disk()).unwrap();
+    let h = fs.create(b"newfile").unwrap();
+    assert_eq!(fs.file_size(h), Some(0));
+    fs.close(h);
+    let mut entries = [DirEntry::empty(); 8];
+    let count = fs.list_dir(b"/", &mut entries).unwrap();
+    assert_eq!(count, 2);
+}
+
+#[test]
+fn write_and_read_back() {
+    let mut fs = Ext4::mount(format_ext4_disk()).unwrap();
+    let h = fs.create(b"writable").unwrap();
+    let written = fs.write(h, b"Hello, world!").unwrap();
+    assert_eq!(written, 13);
+    fs.close(h);
+    let h = fs.open(b"writable").unwrap();
+    let mut buf = [0u8; 32];
+    let n = fs.read(h, &mut buf).unwrap();
+    assert_eq!(n, 13);
+    assert_eq!(&buf[..13], b"Hello, world!");
+    fs.close(h);
+}
+
+#[test]
+fn delete_file_frees_resources() {
+    let mut fs = Ext4::mount(format_ext4_disk()).unwrap();
+    let h = fs.create(b"temp").unwrap();
+    fs.write(h, b"data").unwrap();
+    fs.close(h);
+    assert!(fs.delete(b"temp"));
+    assert!(fs.open(b"temp").is_none());
+    let h2 = fs.create(b"reuse").unwrap();
+    assert!(h2.raw() >= 0);
+    fs.close(h2);
+}
+
+#[test]
+fn create_with_missing_parent_fails() {
+    let mut fs = Ext4::mount(format_ext4_disk()).unwrap();
+    assert!(fs.create(b"nodir/file.txt").is_none());
+}
+
 #[test]
 fn read_past_eof_returns_zero() {
     let mut fs = Ext4::mount(format_ext4_disk()).unwrap();