Re: [PATCH 2/2] mtd: nand: Remove BUG() abuse in nand_scan_tail

Boris Brezillon
2016-04-04T15:21:30Z

On Sat, 2 Apr 2016 15:55:24 +0200
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> On Fri, 1 Apr 2016 18:29:24 -0300
> Ezequiel Garcia <ezequiel@vanguardiasur.com.ar> wrote:
>
> > There's no reason to BUG() when parameters are being
> > validated. Drivers can get things wrong, and it's much nicer
> > to just throw a noisy warn and fail gracefully, than calling
> > BUG() and throwing the whole system down the drain.
>
> I'm fine with this change as long as all callers are checking
> nand_scan_tail() return value.

Actually, the s3c2410 driver is not checking nand_scan_tail() return
value. Could you send a v2 addressing that?

>
> >
> > Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
> > ---
> > drivers/mtd/nand/nand_base.c | 52 ++++++++++++++++++++++++++++----------------
> > 1 file changed, 33 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> > index befa04ef4a04..0fe644ebe264 100644
> > --- a/drivers/mtd/nand/nand_base.c
> > +++ b/drivers/mtd/nand/nand_base.c
> > @@ -4119,10 +4119,12 @@ int nand_scan_tail(struct mtd_info *mtd)
> > struct nand_chip *chip = mtd_to_nand(mtd);
> > struct nand_ecc_ctrl *ecc = &chip->ecc;
> > struct nand_buffers *nbuf;
> > + int ret;
> >
> > /* New bad blocks should be marked in OOB, flash-based BBT, or both */
> > - BUG_ON((chip->bbt_options & NAND_BBT_NO_OOB_BBM) &&
> > - !(chip->bbt_options & NAND_BBT_USE_FLASH));
> > + if (WARN_ON((chip->bbt_options & NAND_BBT_NO_OOB_BBM) &&
> > + !(chip->bbt_options & NAND_BBT_USE_FLASH)))
> > + return -EINVAL;
> >
> > if (!(chip->options & NAND_OWN_BUFFERS)) {
> > nbuf = kzalloc(sizeof(*nbuf) + mtd->writesize
> > @@ -4160,9 +4162,10 @@ int nand_scan_tail(struct mtd_info *mtd)
> > ecc->layout = &nand_oob_128;
> > break;
> > default:
> > - pr_warn("No oob scheme defined for oobsize %d\n",
> > - mtd->oobsize);
> > - BUG();
> > + WARN(1, "No oob scheme defined for oobsize %d\n",
> > + mtd->oobsize);
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> > }
> >
> > @@ -4178,8 +4181,9 @@ int nand_scan_tail(struct mtd_info *mtd)
> > case NAND_ECC_HW_OOB_FIRST:
> > /* Similar to NAND_ECC_HW, but a separate read_page handle */
> > if (!ecc->calculate || !ecc->correct || !ecc->hwctl) {
> > - pr_warn("No ECC functions supplied; hardware ECC not possible\n");
> > - BUG();
> > + WARN(1, "No ECC functions supplied; hardware ECC not possible\n");
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> > if (!ecc->read_page)
> > ecc->read_page = nand_read_page_hwecc_oob_first;
> > @@ -4209,8 +4213,9 @@ int nand_scan_tail(struct mtd_info *mtd)
> > ecc->read_page == nand_read_page_hwecc ||
> > !ecc->write_page ||
> > ecc->write_page == nand_write_page_hwecc)) {
> > - pr_warn("No ECC functions supplied; hardware ECC not possible\n");
> > - BUG();
> > + WARN(1, "No ECC functions supplied; hardware ECC not possible\n");
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> > /* Use standard syndrome read/write page function? */
> > if (!ecc->read_page)
> > @@ -4228,8 +4233,9 @@ int nand_scan_tail(struct mtd_info *mtd)
> >
> > if (mtd->writesize >= ecc->size) {
> > if (!ecc->strength) {
> > - pr_warn("Driver must set ecc.strength when using hardware ECC\n");
> > - BUG();
> > + WARN(1, "Driver must set ecc.strength when using hardware ECC\n");
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> > break;
> > }
> > @@ -4255,8 +4261,9 @@ int nand_scan_tail(struct mtd_info *mtd)
> >
> > case NAND_ECC_SOFT_BCH:
> > if (!mtd_nand_has_bch()) {
> > - pr_warn("CONFIG_MTD_NAND_ECC_BCH not enabled\n");
> > - BUG();
> > + WARN(1, "CONFIG_MTD_NAND_ECC_BCH not enabled\n");
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> > ecc->calculate = nand_bch_calculate_ecc;
> > ecc->correct = nand_bch_correct_data;
> > @@ -4281,8 +4288,9 @@ int nand_scan_tail(struct mtd_info *mtd)
> > ecc->bytes = 0;
> > ecc->priv = nand_bch_init(mtd);
> > if (!ecc->priv) {
> > - pr_warn("BCH ECC initialization failed!\n");
> > - BUG();
> > + WARN(1, "BCH ECC initialization failed!\n");
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> > break;
> >
> > @@ -4300,8 +4308,9 @@ int nand_scan_tail(struct mtd_info *mtd)
> > break;
> >
> > default:
> > - pr_warn("Invalid NAND_ECC_MODE %d\n", ecc->mode);
> > - BUG();
> > + WARN(1, "Invalid NAND_ECC_MODE %d\n", ecc->mode);
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> >
> > /* For many systems, the standard OOB write also works for raw */
> > @@ -4331,8 +4340,9 @@ int nand_scan_tail(struct mtd_info *mtd)
> > */
> > ecc->steps = mtd->writesize / ecc->size;
> > if (ecc->steps * ecc->size != mtd->writesize) {
> > - pr_warn("Invalid ECC parameters\n");
> > - BUG();
> > + WARN(1, "Invalid ECC parameters\n");
> > + ret = -EINVAL;
> > + goto err_free;
> > }
> > ecc->total = ecc->steps * ecc->bytes;
> >
> > @@ -4410,6 +4420,10 @@ int nand_scan_tail(struct mtd_info *mtd)
> >
> > /* Build bad block table */
> > return chip->scan_bbt(mtd);
> > +err_free:
> > + if (!(chip->options & NAND_OWN_BUFFERS))
> > + kfree(chip->buffers);
> > + return ret;
> > }
> > EXPORT_SYMBOL(nand_scan_tail);
> >
>
>
>

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering