write back caching, async writes

write back caching, async writes

[David Chow]

If I want to implement a write back cache or async write in an fs, how 
can I make vfs call back to write by cache or any way to schedule some 
tasks so that the kernel will commit the current task but have a call 
back later? For filesystem methods, it seems it is a process context 
stuff, the only way I can think is to use mark_inode_dirty() so that vfs 
will call my write_inode() super_block_ops so that it works like 
schedule something to write later. If so, how can I retain the page 
cache that has already called to my commit_write() so that those clean 
pages (actually not in disk for async case) can be retained and I can 
make use of those pages when I actuallly sync the data to disk. Or 
should I have a private researved area of buffer to take care of those 
async pages? Please give suggestions. Thanks.

David