Re: [PATCH 7/6] fat: Support a truncate() for expanding size

[Andrew Morton <akpm@osdl.org>]

OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> wrote:
>
> Andrew Morton <akpm@osdl.org> writes:
> 
> > OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> wrote:
> >>
> >> +static int fat_cont_expand(struct inode *inode, loff_t size)
> >
> > Is it not possible to extend generic_cont_expand() so that fatfs can use it?
> 
> The generic_cont_expand() is too generic.

But can it be fixed??

> If "size" is block boundary, generic_cont_expand() expands the
> ->i_size to "size + 1", after it, the caller of it will truncate to
> "size" by vmtruncate().

Something like this?

--- devel/fs/buffer.c~a	2005-11-07 20:17:49.000000000 -0800
+++ devel-akpm/fs/buffer.c	2005-11-07 20:18:59.000000000 -0800
@@ -2160,7 +2160,7 @@ int block_read_full_page(struct page *pa
  * truncates.  Uses prepare/commit_write to allow the filesystem to
  * deal with the hole.  
  */
-int generic_cont_expand(struct inode *inode, loff_t size)
+static int __generic_cont_expand(struct inode *inode, loff_t size, int dont_do_that)
 {
 	struct address_space *mapping = inode->i_mapping;
 	struct page *page;
@@ -2182,9 +2182,8 @@ int generic_cont_expand(struct inode *in
 	** skip the prepare.  make sure we never send an offset for the start
 	** of a block
 	*/
-	if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
+	if (!dont_do_that &&  (offset & (inode->i_sb->s_blocksize - 1)) == 0)
 		offset++;
-	}
 	index = size >> PAGE_CACHE_SHIFT;
 	err = -ENOMEM;
 	page = grab_cache_page(mapping, index);
@@ -2202,6 +2201,16 @@ out:
 	return err;
 }
 
+int generic_cont_expand(struct inode *inode, loff_t size)
+{
+	return __generic_cont_expand(inode, size, 0);
+}
+
+int generic_cont_expand_dont_do_that(struct inode *inode, loff_t size)
+{
+	return __generic_cont_expand(inode, size, 1);
+}
+
 /*
  * For moronic filesystems that do not allow holes in file.
  * We may have to extend the file.
_