kernel: handle bad blocks in ubi auto attach code

The first block(s) of the ubi mtd device might be bad. We need to take
care on our own to skip the bad block(s) and read the next one(s).

Don't treat recoverable read errors as fatal and check for the UBI magic
if the data of a block could be recovered using ECC or similar.

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/generic/pending-4.14/490-ubi-auto-attach-mtd-device-named-ubi-or-data-on-boot.patch

@@ -8,7 +8,7 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
 
 --- a/drivers/mtd/ubi/build.c
 +++ b/drivers/mtd/ubi/build.c
-@@ -1171,6 +1171,54 @@ static struct mtd_info * __init open_mtd
+@@ -1171,6 +1171,68 @@ static struct mtd_info * __init open_mtd
  	return mtd;
  }
  
@@ -20,6 +20,7 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
 +{
 +	int err;
 +	struct mtd_info *mtd;
++	loff_t offset = 0;
 +	size_t len;
 +	char magic[4];
 +
@@ -31,9 +32,22 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
 +	if (IS_ERR(mtd))
 +		return;
 +
++	/* get the first not bad block */
++	if (mtd_can_have_bb(mtd))
++		while (mtd_block_isbad(mtd, offset)) {
++			offset += mtd->erasesize;
++
++			if (offset > mtd->size) {
++				pr_err("UBI error: Failed to find a non-bad "
++				       "block on mtd%d\n", mtd->index);
++				goto cleanup;
++			}
++		}
++
 +	/* check for a valid ubi magic if read from flash was successful */
-+	err = mtd_read(mtd, 0, 4, &len, (void *) magic);
-+	if (!err && len == 4 && strncmp(magic, "UBI#", 4)) {
++	err = mtd_read(mtd, offset, 4, &len, (void *) magic);
++	if ((!err || mtd_is_bitflip(err)) &&
++	    len == 4 && strncmp(magic, "UBI#", 4)) {
 +		pr_err("UBI error: no valid UBI magic found inside mtd%d\n", mtd->index);
 +		goto cleanup;
 +	}
@@ -63,7 +77,7 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
  static int __init ubi_init(void)
  {
  	int err, i, k;
-@@ -1254,6 +1302,12 @@ static int __init ubi_init(void)
+@@ -1254,6 +1316,12 @@ static int __init ubi_init(void)
  		}
  	}
  

target/linux/generic/pending-4.9/490-ubi-auto-attach-mtd-device-named-ubi-or-data-on-boot.patch

@@ -8,7 +8,7 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
 
 --- a/drivers/mtd/ubi/build.c
 +++ b/drivers/mtd/ubi/build.c
-@@ -1226,6 +1226,54 @@ static struct mtd_info * __init open_mtd
+@@ -1226,6 +1226,68 @@ static struct mtd_info * __init open_mtd
  	return mtd;
  }
  
@@ -20,6 +20,7 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
 +{
 +	int err;
 +	struct mtd_info *mtd;
++	loff_t offset = 0;
 +	size_t len;
 +	char magic[4];
 +
@@ -31,9 +32,22 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
 +	if (IS_ERR(mtd))
 +		return;
 +
++	/* get the first not bad block */
++	if (mtd_can_have_bb(mtd))
++		while (mtd_block_isbad(mtd, offset)) {
++			offset += mtd->erasesize;
++
++			if (offset > mtd->size) {
++				pr_err("UBI error: Failed to find a non-bad "
++				       "block on mtd%d\n", mtd->index);
++				goto cleanup;
++			}
++		}
++
 +	/* check for a valid ubi magic if read from flash was successful */
-+	err = mtd_read(mtd, 0, 4, &len, (void *) magic);
-+	if (!err && len == 4 && strncmp(magic, "UBI#", 4)) {
++	err = mtd_read(mtd, offset, 4, &len, (void *) magic);
++	if ((!err || mtd_is_bitflip(err)) &&
++	    len == 4 && strncmp(magic, "UBI#", 4)) {
 +		pr_err("UBI error: no valid UBI magic found inside mtd%d\n", mtd->index);
 +		goto cleanup;
 +	}
@@ -63,7 +77,7 @@ Signed-off-by: Daniel Golle <daniel@makrotopia.org>
  static int __init ubi_init(void)
  {
  	int err, i, k;
-@@ -1309,6 +1357,12 @@ static int __init ubi_init(void)
+@@ -1309,6 +1371,12 @@ static int __init ubi_init(void)
  		}
  	}