[PATCH 1/4] vfs: ftruncate freeze protect backing inode

[Amir Goldstein <amir73il@gmail.com>]

ftruncate an overlayfs inode was wrongly freeze protecting the
overlay file system instead of the backing file system.

Use file_start_write() instead of sb_start_write(), which
does the right thing and will also freeze protect both overlay and
backing fs when the time comes.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/open.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/open.c b/fs/open.c
index 949cef2..53b1b33 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -196,13 +196,13 @@ static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 	if (IS_APPEND(inode))
 		goto out_putf;
 
-	sb_start_write(inode->i_sb);
+	file_start_write(f.file);
 	error = locks_verify_truncate(inode, f.file, length);
 	if (!error)
 		error = security_path_truncate(&f.file->f_path);
 	if (!error)
 		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
-	sb_end_write(inode->i_sb);
+	file_end_write(f.file);
 out_putf:
 	fdput(f);
 out:
-- 
2.7.4