/*
* linux/fs/nfs/write.c
*
* Writing file data over NFS.
*
* We do it like this: When a (user) process wishes to write data to an
* NFS file, a write request is allocated that contains the RPC task data
* plus some info on the page to be written, and added to the inode's
* write chain. If the process writes past the end of the page, an async
* RPC call to write the page is scheduled immediately; otherwise, the call
* is delayed for a few seconds.
*
* Just like readahead, no async I/O is performed if wsize < PAGE_SIZE.
*
* Write requests are kept on the inode's writeback list. Each entry in
* that list references the page (portion) to be written. When the
* cache timeout has expired, the RPC task is woken up, and tries to
* lock the page. As soon as it manages to do so, the request is moved
* from the writeback list to the writelock list.
*
* Note: we must make sure never to confuse the inode passed in the
* write_page request with the one in page->inode. As far as I understand
* it, these are different when doing a swap-out.
*
* To understand everything that goes on here and in the NFS read code,
* one should be aware that a page is locked in exactly one of the following
* cases:
*
* - A write request is in progress.
* - A user process is in generic_file_write/nfs_update_page
* - A user process is in generic_file_read
*
* Also note that because of the way pages are
