Supporting Files With Data

Supporting files with data is simpler then it looks, because we leave most of the work to the page cache, and the VFS's generic page-handling functions.
We simply need to map all address-space operations to functions that invoke the VFS generic page-handling functions, and implement a single function - stamfs_get_block():

• Translate the block offset parameter to the matching disk block number.
• If we succeeded, just return this block number.
• Otherwise - if we were told NOT to allocate a new block, return an error.
• Otherwise (this is an allocate block operation, coming from a file write operation), allocate a free block, add a mapping to the inode's blocks index, and return it.

Originally written by guy keren