Re: [PATCH] mtd: rawnand: serialize lock/unlock against other NAND operations

[William Zhang]

On Thu, Mar 5, 2026 at 11:49 AM Kamal Dasu <kamal.dasu@xxxxxxxxxxxx> wrote:
>
> nand_lock() and nand_unlock() call into chip->ops.lock_area/unlock_area
> without holding the NAND device lock. On controllers that implement
> SET_FEATURES via multiple low-level PIO commands, these can race with
> concurrent UBI/UBIFS background erase/write operations that hold the
> device lock, resulting in cmd_pending conflicts on the NAND controller.
>
> Add nand_get_device()/nand_release_device() around the lock/unlock
> operations to serialize them against all other NAND controller access.
>
> Fixes: 92270086b7e5 ("mtd: rawnand: Add support for manufacturer specific lock/unlock operation")
> Signed-off-by: Kamal Dasu <kamal.dasu@xxxxxxxxxxxx>
> ---
>  drivers/mtd/nand/raw/nand_base.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
> index 38429363251c..dfd8361bdd36 100644
> --- a/drivers/mtd/nand/raw/nand_base.c
> +++ b/drivers/mtd/nand/raw/nand_base.c
> @@ -4737,11 +4737,16 @@ static void nand_shutdown(struct mtd_info *mtd)
>  static int nand_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
>  {
>         struct nand_chip *chip = mtd_to_nand(mtd);
> +       int ret;
>
>         if (!chip->ops.lock_area)
>                 return -ENOTSUPP;
>
> -       return chip->ops.lock_area(chip, ofs, len);
> +       nand_get_device(chip);
> +       ret = chip->ops.lock_area(chip, ofs, len);
> +       nand_release_device(chip);
> +
> +       return ret;
>  }
>
>  /**
> @@ -4753,11 +4758,16 @@ static int nand_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
>  static int nand_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
>  {
>         struct nand_chip *chip = mtd_to_nand(mtd);
> +       int ret;
>
>         if (!chip->ops.unlock_area)
>                 return -ENOTSUPP;
>
> -       return chip->ops.unlock_area(chip, ofs, len);
> +       nand_get_device(chip);
> +       ret = chip->ops.unlock_area(chip, ofs, len);
> +       nand_release_device(chip);
> +
> +       return ret;
>  }
>
>  /* Set default functions */
> --
> 2.34.1
>
Reviewed-by: William Zhang <william.zhang@xxxxxxxxxxxx>