vfs: fix freeze protection in mnt_want_write_file() for overlayfs

The underlying real file used by overlayfs still contains the overlay path.
This results in mnt_want_write_file() calls by the filesystem getting
freeze protection on the wrong inode (the overlayfs one instead of the real
one).

Fix by using file_inode(file)->i_sb instead of file->f_path.mnt->mnt_sb.

Reported-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/namespace.c b/fs/namespace.c
index c16921dba157ca6dd6ad743f47baedeb6392d756..9be2e938d36ffb819d9bce6881fd85bd1e56ef91 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -441,10 +441,10 @@ int mnt_want_write_file(struct file *file)
 {
        int ret;
 
-       sb_start_write(file->f_path.mnt->mnt_sb);
+       sb_start_write(file_inode(file)->i_sb);
        ret = __mnt_want_write_file(file);
        if (ret)
-               sb_end_write(file->f_path.mnt->mnt_sb);
+               sb_end_write(file_inode(file)->i_sb);
        return ret;
 }
 EXPORT_SYMBOL_GPL(mnt_want_write_file);
@@ -486,7 +486,8 @@ void __mnt_drop_write_file(struct file *file)
 
 void mnt_drop_write_file(struct file *file)
 {
-       mnt_drop_write(file->f_path.mnt);
+       __mnt_drop_write_file(file);
+       sb_end_write(file_inode(file)->i_sb);
 }
 EXPORT_SYMBOL(mnt_drop_write_file);