Re: [regression, bisected] Bug 216738 - Adding O_APPEND to O_RDWR with fcntl(fd, F_SETFL) does not work on overlayfs

[Miklos Szeredi]

On Thu, 24 Nov 2022 at 18:03, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:

> So basically we have this
> static int ovl_change_flags(struct file *file, unsigned int flags)
> {
>         struct inode *inode = file_inode(file);
>         int err;
>
>         flags &= OVL_SETFL_MASK;
>
>         if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
>                 return -EPERM;
>
>         if ((flags & O_DIRECT) && !(file->f_mode & FMODE_CAN_ODIRECT))
>                 return -EINVAL;
>
>         if (file->f_op->check_flags) {
>                 err = file->f_op->check_flags(flags);
>                 if (err)
>                         return err;
>         }
>
>         spin_lock(&file->f_lock);
>         file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
>         spin_unlock(&file->f_lock);
>
>         return 0;
> }
> open-coding what setfl() would've done, without updating ->f_iocb_flags...
> Not hard to deal with...
>
> I could pick it in vfs.git #fixes, or Miklos could put it through his tree.
> Miklos, which way would you prefer that to go?

I'll pick this into #overlayfs-next, as a PR for this cycle is needed anyway.

Thanks,
Miklos