fs: kill block_prepare_write

__block_write_begin and block_prepare_write are identical except for slightly
different calling conventions.  Convert all callers to the __block_write_begin
calling conventions and drop block_prepare_write.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/buffer.c b/fs/buffer.c
index 7f0b9b0..a7b8f3c 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1834,9 +1834,11 @@
 }
 EXPORT_SYMBOL(page_zero_new_buffers);
 
-int block_prepare_write(struct page *page, unsigned from, unsigned to,
+int __block_write_begin(struct page *page, loff_t pos, unsigned len,
 		get_block_t *get_block)
 {
+	unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+	unsigned to = from + len;
 	struct inode *inode = page->mapping->host;
 	unsigned block_start, block_end;
 	sector_t block;
@@ -1916,7 +1918,7 @@
 	}
 	return err;
 }
-EXPORT_SYMBOL(block_prepare_write);
+EXPORT_SYMBOL(__block_write_begin);
 
 static int __block_commit_write(struct inode *inode, struct page *page,
 		unsigned from, unsigned to)
@@ -1953,15 +1955,6 @@
 	return 0;
 }
 
-int __block_write_begin(struct page *page, loff_t pos, unsigned len,
-		get_block_t *get_block)
-{
-	unsigned start = pos & (PAGE_CACHE_SIZE - 1);
-
-	return block_prepare_write(page, start, start + len, get_block);
-}
-EXPORT_SYMBOL(__block_write_begin);
-
 /*
  * block_write_begin takes care of the basic task of block allocation and
  * bringing partial write blocks uptodate first.
@@ -2379,7 +2372,7 @@
 	else
 		end = PAGE_CACHE_SIZE;
 
-	ret = block_prepare_write(page, 0, end, get_block);
+	ret = __block_write_begin(page, 0, end, get_block);
 	if (!ret)
 		ret = block_commit_write(page, 0, end);