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, 1 insertions, 2 deletions

diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 6b946bae11cf..764109886ec0 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -450,8 +450,7 @@ ino_t ext2_inode_by_name(struct inode *dir, struct qstr *child)
 
 static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
 {
-        return block_write_begin_newtrunc(NULL, page->mapping, pos, len, 0,
-                                          &page, NULL, ext2_get_block);
+        return __block_write_begin(page, pos, len, ext2_get_block);
 }
 
 /* Releases the page */