fs: remove prepare_write/commit_write

Nothing uses prepare_write or commit_write. Remove them from the tree
completely.

[akpm@linux-foundation.org: schedule simple_prepare_write() for unexporting]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/filesystems/vfs.txt

@@ -492,7 +492,7 @@ written-back to storage typically in whole pages, however the
 address_space has finer control of write sizes.
 
 The read process essentially only requires 'readpage'.  The write
-process is more complicated and uses prepare_write/commit_write or
+process is more complicated and uses write_begin/write_end or
 set_page_dirty to write data into the address_space, and writepage,
 sync_page, and writepages to writeback data to storage.
 
@@ -521,8 +521,6 @@ struct address_space_operations {
 	int (*set_page_dirty)(struct page *page);
 	int (*readpages)(struct file *filp, struct address_space *mapping,
 			struct list_head *pages, unsigned nr_pages);
-	int (*prepare_write)(struct file *, struct page *, unsigned, unsigned);
-	int (*commit_write)(struct file *, struct page *, unsigned, unsigned);
 	int (*write_begin)(struct file *, struct address_space *mapping,
 				loff_t pos, unsigned len, unsigned flags,
 				struct page **pagep, void **fsdata);
@@ -598,37 +596,7 @@ struct address_space_operations {
 	readpages is only used for read-ahead, so read errors are
   	ignored.  If anything goes wrong, feel free to give up.
 
-  prepare_write: called by the generic write path in VM to set up a write
-  	request for a page.  This indicates to the address space that
-  	the given range of bytes is about to be written.  The
-  	address_space should check that the write will be able to
-  	complete, by allocating space if necessary and doing any other
-  	internal housekeeping.  If the write will update parts of
-  	any basic-blocks on storage, then those blocks should be
-  	pre-read (if they haven't been read already) so that the
-  	updated blocks can be written out properly.
-	The page will be locked.
-
-	Note: the page _must not_ be marked uptodate in this function
-	(or anywhere else) unless it actually is uptodate right now. As
-	soon as a page is marked uptodate, it is possible for a concurrent
-	read(2) to copy it to userspace.
-
-  commit_write: If prepare_write succeeds, new data will be copied
-        into the page and then commit_write will be called.  It will
-        typically update the size of the file (if appropriate) and
-        mark the inode as dirty, and do any other related housekeeping
-        operations.  It should avoid returning an error if possible -
-        errors should have been handled by prepare_write.
-
-  write_begin: This is intended as a replacement for prepare_write. The
-	key differences being that:
-		- it returns a locked page (in *pagep) rather than being
-		  given a pre locked page;
-		- it must be able to cope with short writes (where the
-		  length passed to write_begin is greater than the number
-		  of bytes copied into the page).
-
+  write_begin:
 	Called by the generic buffered write code to ask the filesystem to
 	prepare to write len bytes at the given offset in the file. The
 	address_space should check that the write will be able to complete,
@@ -640,6 +608,9 @@ struct address_space_operations {
         The filesystem must return the locked pagecache page for the specified
 	offset, in *pagep, for the caller to write into.
 
+	It must be able to cope with short writes (where the length passed to
+	write_begin is greater than the number of bytes copied into the page).
+
 	flags is a field for AOP_FLAG_xxx flags, described in
 	include/linux/fs.h.