Ext2FS: Inode resizing should fail with ENOSPC if we lack blocks

If there are not enough free blocks in the filesystem to accomodate
growing an Inode, we should fail with ENOSPC before even starting to
allocate blocks.

Kernel/FileSystem/Ext2FileSystem.cpp

@@ -666,7 +666,7 @@ ssize_t Ext2FSInode::read_bytes(off_t offset, ssize_t count, u8* buffer, FileDes
     return nread;
 }
 
-bool Ext2FSInode::resize(u64 new_size)
+KResult Ext2FSInode::resize(u64 new_size)
 {
     u64 block_size = fs().block_size();
     u64 old_size = size();
@@ -678,6 +678,13 @@ bool Ext2FSInode::resize(u64 new_size)
     dbgprintf("Ext2FSInode::resize(): blocks needed after  (size is  %Q): %d\n", new_size, blocks_needed_after);
 #endif
 
+    if (blocks_needed_after > blocks_needed_before) {
+        u32 additional_blocks_needed = blocks_needed_after - blocks_needed_before;
+        if (additional_blocks_needed > fs().super_block().s_free_blocks_count)
+            return KResult(-ENOSPC);
+    }
+
+
     auto block_list = fs().block_list_for_inode(m_raw_inode);
     if (blocks_needed_after > blocks_needed_before) {
         auto new_blocks = fs().allocate_blocks(fs().group_index_from_inode(index()), blocks_needed_after - blocks_needed_before);
@@ -697,13 +704,13 @@ bool Ext2FSInode::resize(u64 new_size)
 
     bool success = fs().write_block_list_for_inode(index(), m_raw_inode, block_list);
     if (!success)
-        return false;
+        return KResult(-EIO);
 
     m_raw_inode.i_size = new_size;
     set_metadata_dirty(true);
 
     m_block_list = move(block_list);
-    return true;
+    return KSuccess;
 }
 
 ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const u8* data, FileDescription*)
@@ -731,8 +738,9 @@ ssize_t Ext2FSInode::write_bytes(off_t offset, ssize_t count, const u8* data, Fi
     u64 old_size = size();
     u64 new_size = max(static_cast<u64>(offset) + count, (u64)size());
 
-    if (!resize(new_size))
-        return -EIO;
+    auto resize_result = resize(new_size);
+    if (resize_result.is_error())
+        return resize_result;
 
     int first_block_logical_index = offset / block_size;
     int last_block_logical_index = (offset + count) / block_size;
@@ -1519,7 +1527,9 @@ KResult Ext2FSInode::truncate(off_t size)
     LOCKER(m_lock);
     if ((off_t)m_raw_inode.i_size == size)
         return KSuccess;
-    resize(size);
+    auto result = resize(size);
+    if (result.is_error())
+        return result;
     set_metadata_dirty(true);
     return KSuccess;
 }

Kernel/FileSystem/Ext2FileSystem.h

@@ -47,7 +47,7 @@ private:
 
     bool write_directory(const Vector<FS::DirectoryEntry>&);
     void populate_lookup_cache() const;
-    bool resize(u64);
+    KResult resize(u64);
 
     Ext2FS& fs();
     const Ext2FS& fs() const;