introduce __block_write_begin

Split up the block_write_begin implementation - __block_write_begin is a new
trivial wrapper for block_prepare_write that always takes an already
allocated page and can be either called from block_write_begin or filesystem
code that already has a page allocated.  Remove the handling of already
allocated pages from block_write_begin after switching all callers that
do it to __block_write_begin.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 7638647f0424..accc9f81bb63 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -209,6 +209,8 @@ int block_write_begin_newtrunc(struct file *, struct address_space *,
 int block_write_begin(struct file *, struct address_space *,
                                 loff_t, unsigned, unsigned,
                                 struct page **, void **, get_block_t*);
+int __block_write_begin(struct page *page, loff_t pos, unsigned len,
+                get_block_t *get_block);
 int block_write_end(struct file *, struct address_space *,
                                 loff_t, unsigned, unsigned,
                                 struct page *, void *);