Re: [PATCH v4 1/2] hugetlb: use f_mode & FMODE_HUGETLBFS to identify hugetlbfs files

[Miklos Szeredi]

On Sat, Jun 13, 2020 at 8:53 AM Amir Goldstein <amir73il@xxxxxxxxx> wrote:

> > I also looked at normal filesystem lower and hugetlbfs upper.  Yes, overlayfs
> > allows this.  This is somewhat 'interesting' as write() is not supported in
> > hugetlbfs.  Writing to files in the overlay actually ended up writing to
> > files in the lower filesystem.  That seems wrong, but overlayfs is new to me.

Yes, this very definitely should not happen.

> I am not sure how that happened, but I think that ovl_open_realfile()
> needs to fixup f_mode flags FMODE_CAN_WRITE | FMODE_CAN_READ
> after open_with_fake_path().

Okay, but how did the write actually get to the lower layer?

I failed to reproduce this.  Mike, how did you trigger this?

Thanks,
Miklos