On Mon, Sep 19, 2022 at 04:10:27PM +0200, Miklos Szeredi wrote:
> If tmpfile is used for copy up, then use this helper to create the tmpfile
> and open it at the same time. This will later allow filesystems such as
> fuse to do this operation atomically.
>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
> ---
> fs/overlayfs/copy_up.c | 49 ++++++++++++++++++++++------------------
> fs/overlayfs/overlayfs.h | 12 ++++++----
> fs/overlayfs/super.c | 10 ++++----
> 3 files changed, 40 insertions(+), 31 deletions(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index fdde6c56cc3d..ac087b48b5da 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -194,16 +194,16 @@ static int ovl_copy_fileattr(struct inode *inode, struct path *old,
> }
>
> static int ovl_copy_up_data(struct ovl_fs *ofs, struct path *old,
> - struct path *new, loff_t len)
> + struct path *new, struct file *new_file, loff_t len)
> {
Ugh... Lift opening into both callers and get rid of struct path *new,
please. Would be much easier to follow that way...
> - err = ovl_copy_up_inode(c, temp);
> + err = ovl_copy_up_inode(c, temp, NULL);
FWIW, I would consider passing a struct file * in all cases, with O_PATH
for non-regular ones...
> - temp = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0);
> - ofs->tmpfile = !IS_ERR(temp);
> + tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0);
> + ofs->tmpfile = !IS_ERR(tmpfile);
> if (ofs->tmpfile)
> - dput(temp);
> + fput(tmpfile);
Careful - that part essentially checks if we have a working
->tmpfile(), but we rely upon more than just having it - we want
dentry-based setxattr() and friends to work after O_TMPFILE.
Are we making that a requirement for ->tmpfile()? I.e. that
after O_TMPFILE open notify_change() et.al. on its dentry
will work *without* corresponding struct file. In particular,
fuse seems to check for ATTR_FILE...
