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Message-ID: <20160429173417.GA18490@senary>
Date: Fri, 29 Apr 2016 12:34:18 -0500
From: Kyle Roeschley <kyle.roeschley@...com>
To: Boris Brezillon <boris.brezillon@...e-electrons.com>
CC: <richard@....at>, <nathan.sullivan@...com>, <xander.huff@...com>,
<linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
<computersforpeace@...il.com>, <dwmw2@...radead.org>,
<beanhuo@...ron.com>, Peter Pan <peterpansjtu@...il.com>
Subject: Re: [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@...e-electrons.com> wrote:
>
> > Hi Kyle,
> >
> > On Fri, 25 Mar 2016 17:31:16 -0500
> > Kyle Roeschley <kyle.roeschley@...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@...com>.
> > >
> > > Signed-off-by: Kyle Roeschley <kyle.roeschley@...com>
> > > Suggested-by: Jeff Westfahl <jeff.westfahl@...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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