Re: [PATCH 2/3] ntfs: wake free-cluster waiters when precalc allocation fails

[Hyunchul Lee]

2026년 5월 21일 (목) 오전 2:02, DaeMyung Kang <charsyam@xxxxxxxxx>님이 작성:
>
> get_nr_free_clusters() is run from the precalc_free_clusters() worker
> queued at the end of ntfs_fill_super().  It is also the only place that
> publishes the result by atomic64_set(&vol->free_clusters, ...), sets
> NVolSetFreeClusterKnown(), and wakes vol->free_waitq.
>
> The initial kzalloc(sizeof(*ra), ...) can fail before that publication
> happens.  Callers that need the free count wait on NVolFreeClusterKnown(),
> so this failure can leave statfs, write, and allocation paths blocked
> forever.
>
> On the OOM path, publish a conservative free count of zero, initialize
> the per-bitmap-page free counters to zero, set NVolFreeClusterKnown, and
> wake the wait queue so callers fail with -ENOSPC rather than block
> forever.
>
> Signed-off-by: DaeMyung Kang <charsyam@xxxxxxxxx>
> ---
>  super.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/super.c b/super.c
> index 6cf09bbe017d..c90cb5673f98 100644
> --- a/super.c
> +++ b/super.c
> @@ -1980,8 +1980,23 @@ s64 get_nr_free_clusters(struct ntfs_volume *vol)
>                 return atomic64_read(&vol->free_clusters);
>
>         ra = kzalloc(sizeof(*ra), GFP_NOFS);
> -       if (!ra)

How about declaring ra as a stack variable?

> +       if (!ra) {
> +               max_index = (((vol->nr_clusters + 7) >> 3) +
> +                               PAGE_SIZE - 1) >> PAGE_SHIFT;
> +
> +               /*
> +                * Publish a conservative free count and wake any waiters; the
> +                * NVolFreeClusterKnown flag is the sole signal the wait_event
> +                * loops in statfs/allocation paths use, so failing to set it
> +                * here would leave those callers blocked forever.
> +                */
> +               memset(vol->lcn_empty_bits_per_page, 0,
> +                      max_index * sizeof(*vol->lcn_empty_bits_per_page));
> +               atomic64_set(&vol->free_clusters, 0);
> +               NVolSetFreeClusterKnown(vol);
> +               wake_up_all(&vol->free_waitq);
>                 return 0;
> +       }
>
>         file_ra_state_init(ra, mapping);
>
> --
> 2.43.0
>


--
Thanks,
Hyunchul