Re: [PATCH 14/18] lightnvm: pblk: GC error handling

[Hans Holmberg <hans@owltronix.com>]

On Thu, Mar 14, 2019 at 5:09 PM Igor Konopko <igor.j.konopko@intel.com> wrote:
>
> Currently when there is an IO error (or similar) on GC read path, pblk
> still moves this line to free state, what leads to data mismatch issue.
>
> This patch adds a handling for such an error - after that changes this
> line will be returned to closed state so it can be still in use
> for reading - at least we will be able to return error status to user
> when user tries to read such a data.
>
> Signed-off-by: Igor Konopko <igor.j.konopko@intel.com>
> ---
>  drivers/lightnvm/pblk-core.c | 8 ++++++++
>  drivers/lightnvm/pblk-gc.c   | 5 ++---
>  drivers/lightnvm/pblk-read.c | 1 -
>  drivers/lightnvm/pblk.h      | 2 ++
>  4 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> index 4d5cd99..6817f8f 100644
> --- a/drivers/lightnvm/pblk-core.c
> +++ b/drivers/lightnvm/pblk-core.c
> @@ -1786,6 +1786,14 @@ static void __pblk_line_put(struct pblk *pblk, struct pblk_line *line)
>
>         spin_lock(&line->lock);
>         WARN_ON(line->state != PBLK_LINESTATE_GC);
> +       if (line->w_err_gc->has_gc_err) {
> +               spin_unlock(&line->lock);
> +               pblk_err(pblk, "line %d had errors during GC\n", line->id);
> +               pblk_put_line_back(pblk, line);
> +               line->w_err_gc->has_gc_err = 0;

In a real bummer corner case, the line might have had a write error as well
(line->w_err_gc->has_write_err == true)

In that case we need to inform the rate limiter:
pblk_rl_werr_line_out(&pblk->rl);

> +               return;
> +       }
> +
>         line->state = PBLK_LINESTATE_FREE;
>         trace_pblk_line_state(pblk_disk_name(pblk), line->id,
>                                         line->state);
> diff --git a/drivers/lightnvm/pblk-gc.c b/drivers/lightnvm/pblk-gc.c
> index e23b192..63ee205 100644
> --- a/drivers/lightnvm/pblk-gc.c
> +++ b/drivers/lightnvm/pblk-gc.c
> @@ -59,7 +59,7 @@ static void pblk_gc_writer_kick(struct pblk_gc *gc)
>         wake_up_process(gc->gc_writer_ts);
>  }
>
> -static void pblk_put_line_back(struct pblk *pblk, struct pblk_line *line)
> +void pblk_put_line_back(struct pblk *pblk, struct pblk_line *line)
>  {
>         struct pblk_line_mgmt *l_mg = &pblk->l_mg;
>         struct list_head *move_list;
> @@ -98,8 +98,7 @@ static void pblk_gc_line_ws(struct work_struct *work)
>         /* Read from GC victim block */
>         ret = pblk_submit_read_gc(pblk, gc_rq);
>         if (ret) {
> -               pblk_err(pblk, "failed GC read in line:%d (err:%d)\n",
> -                                                               line->id, ret);
> +               line->w_err_gc->has_gc_err = 1;
>                 goto out;
>         }
>
> diff --git a/drivers/lightnvm/pblk-read.c b/drivers/lightnvm/pblk-read.c
> index 54422a2..6a77c24 100644
> --- a/drivers/lightnvm/pblk-read.c
> +++ b/drivers/lightnvm/pblk-read.c
> @@ -475,7 +475,6 @@ int pblk_submit_read_gc(struct pblk *pblk, struct pblk_gc_rq *gc_rq)
>
>         if (pblk_submit_io_sync(pblk, &rqd)) {
>                 ret = -EIO;
> -               pblk_err(pblk, "GC read request failed\n");
>                 goto err_free_bio;
>         }
>
> diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
> index 5d1040a..52002f5 100644
> --- a/drivers/lightnvm/pblk.h
> +++ b/drivers/lightnvm/pblk.h
> @@ -427,6 +427,7 @@ struct pblk_smeta {
>
>  struct pblk_w_err_gc {
>         int has_write_err;
> +       int has_gc_err;
>         __le64 *lba_list;
>  };
>
> @@ -909,6 +910,7 @@ void pblk_gc_free_full_lines(struct pblk *pblk);
>  void pblk_gc_sysfs_state_show(struct pblk *pblk, int *gc_enabled,
>                               int *gc_active);
>  int pblk_gc_sysfs_force(struct pblk *pblk, int force);
> +void pblk_put_line_back(struct pblk *pblk, struct pblk_line *line);
>
>  /*
>   * pblk rate limiter
> --
> 2.9.5
>