ocfs2: fix zero out valid data

If append-dio feature is enabled, direct-io write and fallocate could
run in parallel to extend file size, fallocate used "orig_isize" to
record i_size before taking "ip_alloc_sem", when
ocfs2_zeroout_partial_cluster() zeroout EOF blocks, i_size maybe already
extended by ocfs2_dio_end_io_write(), that will cause valid data zeroed
out.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 6bba447 ("ocfs2: fix data corruption by fallocate")
Signed-off-by: Junxiao Bi <[email protected]>
Reviewed-by: Joseph Qi <[email protected]>
Cc: Changwei Ge <[email protected]>
Cc: Gang He <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Jun Piao <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: biger410

fs/ocfs2/file.c

@@ -1935,15 +1935,14 @@ static int __ocfs2_change_file_space(struct file *file, struct inode *inode,
 		goto out_inode_unlock;
 	}
 
-	orig_isize = i_size_read(inode);
 	switch (sr->l_whence) {
 	case 0: /*SEEK_SET*/
 		break;
 	case 1: /*SEEK_CUR*/
 		sr->l_start += f_pos;
 		break;
 	case 2: /*SEEK_END*/
-		sr->l_start += orig_isize;
+		sr->l_start += i_size_read(inode);
 		break;
 	default:
 		ret = -EINVAL;
@@ -1998,6 +1997,7 @@ static int __ocfs2_change_file_space(struct file *file, struct inode *inode,
 		ret = -EINVAL;
 	}
 
+	orig_isize = i_size_read(inode);
 	/* zeroout eof blocks in the cluster. */
 	if (!ret && change_size && orig_isize < size) {
 		ret = ocfs2_zeroout_partial_cluster(inode, orig_isize,