exofs: simple_write_end does not mark_inode_dirty

exofs uses simple_write_end() for it's .write_end handler. But
it is not enough because simple_write_end() does not call
mark_inode_dirty() when it extends i_size. So even if we do
call mark_inode_dirty at beginning of write out, with a very
long IO and a saturated system we might get the .write_inode()
called while still extend-writing to file and miss out on the last
i_size updates.

So override .write_end, call simple_write_end(), and afterwords if
i_size was changed call mark_inode_dirty().

It stands to logic that since simple_write_end() was the one extending
i_size it should also call mark_inode_dirty(). But it looks like all
users of simple_write_end() are memory-bound pseudo filesystems, who
could careless about mark_inode_dirty(). I might submit a
warning-comment patch to simple_write_end() in future.

CC: Stable <stable@kernel.org>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

fs/exofs/inode.c

@@ -738,13 +738,28 @@ static int exofs_write_begin_export(struct file *file,
 					fsdata);
 }
 
+static int exofs_write_end(struct file *file, struct address_space *mapping,
+			loff_t pos, unsigned len, unsigned copied,
+			struct page *page, void *fsdata)
+{
+	struct inode *inode = mapping->host;
+	/* According to comment in simple_write_end i_mutex is held */
+	loff_t i_size = inode->i_size;
+	int ret;
+
+	ret = simple_write_end(file, mapping,pos, len, copied, page, fsdata);
+	if (i_size != inode->i_size)
+		mark_inode_dirty(inode);
+	return ret;
+}
+
 const struct address_space_operations exofs_aops = {
 	.readpage	= exofs_readpage,
 	.readpages	= exofs_readpages,
 	.writepage	= exofs_writepage,
 	.writepages	= exofs_writepages,
 	.write_begin	= exofs_write_begin_export,
-	.write_end	= simple_write_end,
+	.write_end	= exofs_write_end,
 };
 
 /******************************************************************************