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/sysv/itree.c b/fs/sysv/itree.c
index 4068f485cfd6..82a005c3d7eb 100644
--- a/fs/sysv/itree.c
+++ b/fs/sysv/itree.c
@@ -461,8 +461,7 @@ static int sysv_readpage(struct file *file, struct page *page)
 
 int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
 {
-        return block_write_begin_newtrunc(NULL, page->mapping, pos, len, 0,
-                                          &page, NULL, get_block);
+        return __block_write_begin(page, pos, len, get_block);
 }
 
 static int sysv_write_begin(struct file *file, struct address_space *mapping,