Re: [PATCH] ntfs: mount read-only when mft records are smaller than the device block

[Namjae Jeon]

On Tue, Aug 25, 2026 at 2:47 PM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>
> On Sun, Aug 23, 2026 at 10:45:48AM -0700, Dennis Tighe wrote:
> > An mft record is written with a single bio of exactly mft_record_size
> > bytes. bio_unaligned() rejects a bio whose size is not a multiple of the
> > device's logical block size, so on a volume whose mft records are smaller
> > than that block no mft record can be written at all.
> >
> > On 512n and 512e drives this is a non-issue; however, on 4Kn drives when
> > the mft record (1k) is smaller than the logical block size (4k) mft
> > writes begin to fail. At the same time, other writes that use all 4k
> > will succeed leading to a corruption situation.
> >
> > This is a stopgap change that mounts as read-only. The longer term fix is
> > to perform 4k writes on 4Kn devices when writing the mft; however, that's
> > more involved.
>
> Between this and your previous patch it is pretty clear that a sector
> size > 512 bytes is not supported.  So instead of adding predicted
> band aids, reject this entirely for now and let someone who has the time
> actually understand this for real fix it with a real design test plan
> and all the others bits needed.
NTFS previously supported 4K native, so this seems to be a regression
introduced by some changes.
We will look into it a bit more and then decide whether to reject the mount.
Thanks!