ovl: implement tmpfile

Combine inode creation with opening a file.

There are six separate objects that are being set up: the backing inode,
dentry and file, and the overlay inode, dentry and file.  Cleanup in case
of an error is a bit of a challenge and is difficult to test, so careful
review is needed.

All tmpfile testcases except generic/509 now run/pass, and no regressions
are observed with full xfstests.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/backing-file.h b/include/linux/backing-file.h
index 3f1fe1774f1b..4b61b0e57720 100644
--- a/include/linux/backing-file.h
+++ b/include/linux/backing-file.h
@@ -22,6 +22,9 @@ struct backing_file_ctx {
 struct file *backing_file_open(const struct path *user_path, int flags,
 			       const struct path *real_path,
 			       const struct cred *cred);
+struct file *backing_tmpfile_open(const struct path *user_path, int flags,
+				  const struct path *real_parentpath,
+				  umode_t mode, const struct cred *cred);
 ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
 			       struct kiocb *iocb, int flags,
 			       struct backing_file_ctx *ctx);