[PATCH] fat: support a truncate() for expanding size (generic_cont_expand)

This patch changes generic_cont_expand(), in order to share the code
with fatfs.

  - Use vmtruncate() if ->prepare_write() returns a error.

Even if ->prepare_write() returns an error, it may already have added some
blocks.  So, this truncates blocks outside of ->i_size by vmtruncate().

  - Add generic_cont_expand_simple().

The generic_cont_expand_simple() assumes that ->prepare_write() can handle
the block boundary.  With this, we don't need to care the extra byte.

And for expanding a file size by truncate(), fatfs uses the
added generic_cont_expand_simple().

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 1db061b..9f159ba 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -197,7 +197,8 @@ int block_read_full_page(struct page*, get_block_t*);
 int block_prepare_write(struct page*, unsigned, unsigned, get_block_t*);
 int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*,
 				loff_t *);
-int generic_cont_expand(struct inode *inode, loff_t size) ;
+int generic_cont_expand(struct inode *inode, loff_t size);
+int generic_cont_expand_simple(struct inode *inode, loff_t size);
 int block_commit_write(struct page *page, unsigned from, unsigned to);
 int block_sync_page(struct page *);
 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);