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

[Kyle Roeschley]

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 at ni.com>.

Signed-off-by: Kyle Roeschley <kyle.roeschley at ni.com>
Suggested-by: Jeff Westfahl <jeff.westfahl at 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) {
 		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:
 
 		/*
 		 * 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);
+			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]);
-- 
2.8.0.rc3