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    SubjectRe: [PATCH v3] mtd: nand_bbt: scan for next free bbt block if writing bbt fails
    Hi Boris,

    On Wed, Mar 30, 2016 at 03:16:23PM +0200, Boris Brezillon wrote:
    > +Peter, who's currently reworking the NAND BBT code.
    >
    > On Wed, 30 Mar 2016 15:13:51 +0200
    > Boris Brezillon <boris.brezillon@free-electrons.com> wrote:
    >
    > > Hi Kyle,
    > >
    > > On Fri, 25 Mar 2016 17:31:16 -0500
    > > Kyle Roeschley <kyle.roeschley@ni.com> wrote:
    > >
    > > > If erasing or writing the BBT fails, we should mark the current BBT
    > > > block as bad and use the BBT descriptor to scan for the next available
    > > > unused block in the BBT. We should only return a failure if there isn't
    > > > any space left.
    > > >
    > > > Based on original code implemented by Jeff Westfahl
    > > > <jeff.westfahl@ni.com>.
    > > >
    > > > Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
    > > > Suggested-by: Jeff Westfahl <jeff.westfahl@ni.com>
    > > > ---
    > > > This v3 is in response to comments from Brian Norris and Bean Ho on 8/26/15:
    > > > http://lists.infradead.org/pipermail/linux-mtd/2015-August/061411.html
    > > >
    > > > v3: Don't overload mtd->priv
    > > > Keep nand_erase_nand from erroring on protected BBT blocks
    > > >
    > > > v2: Mark OOB area in each block as well as BBT
    > > > Avoid marking read-only, bad address, or known bad blocks as bad
    > > > ---
    > > > drivers/mtd/nand/nand_base.c | 4 ++--
    > > > drivers/mtd/nand/nand_bbt.c | 37 +++++++++++++++++++++++++++++++++++--
    > > > 2 files changed, 37 insertions(+), 4 deletions(-)
    > > >
    > > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
    > > > index b6facac..9ad8a86 100644
    > > > --- a/drivers/mtd/nand/nand_base.c
    > > > +++ b/drivers/mtd/nand/nand_base.c
    > > > @@ -2916,8 +2916,8 @@ int nand_erase_nand(struct mtd_info *mtd, struct erase_info *instr,
    > > > /* Select the NAND device */
    > > > chip->select_chip(mtd, chipnr);
    > > >
    > > > - /* Check, if it is write protected */
    > > > - if (nand_check_wp(mtd)) {
    > > > + /* Check if it is write protected, unless we're erasing BBT */
    > > > + if (nand_check_wp(mtd) && !allowbbt) {
    > >
    > > Hm, will this really work. Can a write-protected device accept erase
    > > commands?
    > >

    Having looked into this more, no. Since v2, we called block_markbad in
    write_bbt incorrectly and caused the chip to report that it was write
    protected. Fixing that makes this unnecessary.

    > > > pr_debug("%s: device is write protected!\n",
    > > > __func__);
    > > > instr->state = MTD_ERASE_FAILED;
    > > > diff --git a/drivers/mtd/nand/nand_bbt.c b/drivers/mtd/nand/nand_bbt.c
    > > > index 2fbb523..01526e5 100644
    > > > --- a/drivers/mtd/nand/nand_bbt.c
    > > > +++ b/drivers/mtd/nand/nand_bbt.c
    > > > @@ -662,6 +662,7 @@ static int write_bbt(struct mtd_info *mtd, uint8_t *buf,
    > > > page = td->pages[chip];
    > > > goto write;
    > > > }
    > > > + next:
    > >
    > > Please put this label at the beginning of the line and fix all the other
    > > issues reported by checkpatch (I know we already have a 'write' label
    > > which does not follow this rule, but let's try to avoid adding new
    > > ones).
    > >

    Will do.

    > > >
    > > > /*
    > > > * Automatic placement of the bad block table. Search direction
    > > > @@ -787,14 +788,46 @@ static int write_bbt(struct mtd_info *mtd, uint8_t *buf,
    > > > einfo.addr = to;
    > > > einfo.len = 1 << this->bbt_erase_shift;
    > > > res = nand_erase_nand(mtd, &einfo, 1);
    > > > - if (res < 0)
    > > > + if (res == -EIO) {
    > > > + /* This block is bad. Mark it as such and see if
    > > > + * there's another block available in the BBT area. */
    > > > + int block = page >>
    > > > + (this->bbt_erase_shift - this->page_shift);
    > > > + pr_info("nand_bbt: failed to erase block %d when writing BBT\n",
    > > > + block);
    > > > + bbt_mark_entry(this, block, BBT_BLOCK_WORN);
    > > > +
    > > > + res = this->block_markbad(mtd, block);
    > >
    > > Not sure we should mark the block bad until we managed to write a new
    > > BBT. ITOH, if we do so and the new BBT write is interrupted, it
    > > will trigger a full BBM scan, which should be harmless on most
    > > platforms (except those overwriting BBM with real data :-/)
    > >

    So is your suggestion here just to swap the order of block_markbad and
    bbt_mark_entry?

    > > > + if (res)
    > > > + pr_warn("nand_bbt: error %d while marking block %d bad\n",
    > > > + res, block);
    > > > + td->pages[chip] = -1;
    > > > + goto next;
    > > > + } else if (res < 0) {
    > > > goto outerr;
    > > > + }
    > > >
    > > > res = scan_write_bbt(mtd, to, len, buf,
    > > > td->options & NAND_BBT_NO_OOB ? NULL :
    > > > &buf[len]);
    > > > - if (res < 0)
    > > > + if (res == -EIO) {
    > > > + /* This block is bad. Mark it as such and see if
    > > > + * there's another block available in the BBT area. */
    > > > + int block = page >>
    > > > + (this->bbt_erase_shift - this->page_shift);
    > > > + pr_info("nand_bbt: failed to write block %d when writing BBT\n",
    > > > + block);
    > > > + bbt_mark_entry(this, block, BBT_BLOCK_WORN);
    > > > +
    > > > + res = this->block_markbad(mtd, block);
    > > > + if (res)
    > > > + pr_warn("nand_bbt: error %d while marking block %d bad\n",
    > > > + res, block);
    > > > + td->pages[chip] = -1;
    > > > + goto next;
    > > > + } else if (res < 0) {
    > > > goto outerr;
    > > > + }
    > > >
    > > > pr_info("Bad block table written to 0x%012llx, version 0x%02X\n",
    > > > (unsigned long long)to, td->version[chip]);
    > >
    > > Bean, Brian, can you comment on this new version. I haven't followed
    > > the previous iterations, and would like to have your feedback before
    > > taking a decision.
    > >
    > > Thanks,
    > >
    > > Boris
    > >
    > >
    >
    >
    >
    > --
    > Boris Brezillon, Free Electrons
    > Embedded Linux and Kernel engineering
    > http://free-electrons.com

    Thanks for the feedback,

    --
    Kyle Roeschley
    Software Engineer
    National Instruments

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