NFS: Fixup some outdated comments...

/*

 * 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 invalidated in

 * nfs_revalidate_inode, the following assertions hold:

 *

 *  -	If a page is dirty, there will be no read requests (a page will

 *	not be re-read unless invalidated by nfs_revalidate_inode).

 *  -	If the page is not uptodate, there will be no pending write

 *	requests, and no process will be in nfs_update_page.

 *

 * FIXME: Interaction with the vmscan routines is not optimal yet.

 * Either vmscan must be made nfs-savvy, or we need a different page

 * reclaim concept that supports something like FS-independent

 * buffer_heads with a b_ops-> field.

 * Write file data over NFS.

 *

 * Copyright (C) 1996, 1997, Olaf Kirch <okir@monad.swb.de>

 */