Re: [PATCH v5 1/4] kernfs: add a WARN_ON_ONCE if ->close is set

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Aug 09, 2024 at 09:41:48AM -0600, Martin Oliveira wrote:
> On 2024-08-08 23:37, Greg Kroah-Hartman wrote:
> >> diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
> >> index 8502ef68459b..72cc51dcf870 100644
> >> --- a/fs/kernfs/file.c
> >> +++ b/fs/kernfs/file.c
> >> @@ -479,7 +479,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
> >>        * It is not possible to successfully wrap close.
> >>        * So error if someone is trying to use close.
> >>        */
> >> -     if (vma->vm_ops && vma->vm_ops->close)
> >> +     if (WARN_ON_ONCE(vma->vm_ops && vma->vm_ops->close))
> > 
> > So you just rebooted a machine that hits this, loosing data everywhere.
> > Not nice :(
> 
> Well, apologies for that, but there's no way to know what every single machine
> out there is doing...
> 
> However if this machine is using ->close when that's clearly marked as
> unsupported then shouldn't we fix that?

return an error properly?