1 files changed, 83 insertions, 62 deletions

diff --git a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c
index fba3dc6a..19dc5e0 100644
--- a/drivers/mtd/ubi/scan.c
+++ b/drivers/mtd/ubi/scan.c
@@ -29,7 +29,7 @@
  * objects which are kept in volume RB-tree with root at the @volumes field.
  * The RB-tree is indexed by the volume ID.
  *
- * Found logical eraseblocks are represented by &struct ubi_scan_leb objects.
+ * Scanned logical eraseblocks are represented by &struct ubi_scan_leb objects.
  * These objects are kept in per-volume RB-trees with the root at the
  * corresponding &struct ubi_scan_volume object. To put it differently, we keep
  * an RB-tree of per-volume objects and each of these objects is the root of
@@ -38,6 +38,21 @@
  * Corrupted physical eraseblocks are put to the @corr list, free physical
  * eraseblocks are put to the @free list and the physical eraseblock to be
  * erased are put to the @erase list.
+ *
+ * UBI tries to distinguish between 2 types of corruptions.
+ * 1. Corruptions caused by power cuts. These are harmless and expected
+ *    corruptions and UBI tries to handle them gracefully, without printing too
+ *    many warnings and error messages. The idea is that we do not lose
+ *    important data in these case - we may lose only the data which was being
+ *    written to the media just before the power cut happened, and the upper
+ *    layers are supposed to handle these situations. UBI puts these PEBs to
+ *    the head of the @erase list and they are scheduled for erasure.
+ *
+ * 2. Unexpected corruptions which are not caused by power cuts. During
+ *    scanning, such PEBs are put to the @corr list and UBI preserves them.
+ *    Obviously, this lessens the amount of available PEBs, and if at some
+ *    point UBI runs out of free PEBs, it switches to R/O mode. UBI also loudly
+ *    informs about such PEBs every time the MTD device is attached.
  */
 
 #include <linux/err.h>
@@ -62,23 +77,26 @@ static struct ubi_vid_hdr *vidh;
  * @si: scanning information
  * @pnum: physical eraseblock number to add
  * @ec: erase counter of the physical eraseblock
+ * @to_head: if not zero, add to the head of the list
  * @list: the list to add to
  *
  * This function adds physical eraseblock @pnum to free, erase, or alien lists.
- * Returns zero in case of success and a negative error code in case of
+ * If @to_head is not zero, PEB will be added to the head of the list, which
+ * basically means it will be processed first later. E.g., we add corrupted
+ * PEBs (corrupted due to power cuts) to the head of the erase list to make
+ * sure we erase them first and get rid of corruptions ASAP. This function
+ * returns zero in case of success and a negative error code in case of
  * failure.
  */
-static int add_to_list(struct ubi_scan_info *si, int pnum, int ec,
+static int add_to_list(struct ubi_scan_info *si, int pnum, int ec, int to_head,
 		       struct list_head *list)
 {
 	struct ubi_scan_leb *seb;
 
 	if (list == &si->free) {
 		dbg_bld("add to free: PEB %d, EC %d", pnum, ec);
-		si->free_peb_count += 1;
 	} else if (list == &si->erase) {
 		dbg_bld("add to erase: PEB %d, EC %d", pnum, ec);
-		si->erase_peb_count += 1;
 	} else if (list == &si->alien) {
 		dbg_bld("add to alien: PEB %d, EC %d", pnum, ec);
 		si->alien_peb_count += 1;
@@ -91,7 +109,10 @@ static int add_to_list(struct ubi_scan_info *si, int pnum, int ec,
 
 	seb->pnum = pnum;
 	seb->ec = ec;
-	list_add_tail(&seb->u.list, list);
+	if (to_head)
+		list_add(&seb->u.list, list);
+	else
+		list_add_tail(&seb->u.list, list);
 	return 0;
 }
 
@@ -282,8 +303,8 @@ static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
 		 * created before sequence numbers support has been added. At
 		 * that times we used 32-bit LEB versions stored in logical
 		 * eraseblocks. That was before UBI got into mainline. We do not
-		 * support these images anymore. Well, those images will work
-		 * still work, but only if no unclean reboots happened.
+		 * support these images anymore. Well, those images still work,
+		 * but only if no unclean reboots happened.
 		 */
 		ubi_err("unsupported on-flash UBI format\n");
 		return -EINVAL;
@@ -321,7 +342,7 @@ static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
 				bitflips = 1;
 			else {
 				dbg_err("VID of PEB %d header is bad, but it "
-					"was OK earlier", pnum);
+					"was OK earlier, err %d", pnum, err);
 				if (err > 0)
 					err = -EIO;
 
@@ -487,11 +508,8 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 			if (err)
 				return err;
 
-			if (cmp_res & 4)
-				err = add_corrupted(si, seb->pnum, seb->ec);
-			else
-				err = add_to_list(si, seb->pnum, seb->ec,
-						  &si->erase);
+			err = add_to_list(si, seb->pnum, seb->ec, cmp_res & 4,
+					  &si->erase);
 			if (err)
 				return err;
 
@@ -510,10 +528,8 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 			 * This logical eraseblock is older than the one found
 			 * previously.
 			 */
-			if (cmp_res & 4)
-				return add_corrupted(si, pnum, ec);
-			else
-				return add_to_list(si, pnum, ec, &si->erase);
+			return add_to_list(si, pnum, ec, cmp_res & 4,
+					   &si->erase);
 		}
 	}
 
@@ -544,7 +560,6 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 	sv->leb_count += 1;
 	rb_link_node(&seb->u.rb, parent, p);
 	rb_insert_color(&seb->u.rb, &sv->root);
-	si->used_peb_count += 1;
 	return 0;
 }
 
@@ -776,10 +791,14 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
 		bitflips = 1;
 		break;
 	case UBI_IO_FF:
+		si->empty_peb_count += 1;
+		return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, 0,
+				   &si->erase);
 	case UBI_IO_FF_BITFLIPS:
-		return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, &si->erase);
+		si->empty_peb_count += 1;
+		return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, 1,
+				   &si->erase);
 	case UBI_IO_BAD_HDR_EBADMSG:
-		si->read_err_count += 1;
 	case UBI_IO_BAD_HDR:
 		/*
 		 * We have to also look at the VID header, possibly it is not
@@ -855,18 +874,25 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
 		bitflips = 1;
 		break;
 	case UBI_IO_BAD_HDR_EBADMSG:
-		si->read_err_count += 1;
+		if (ec_err == UBI_IO_BAD_HDR_EBADMSG)
+			/*
+			 * Both EC and VID headers are corrupted and were read
+			 * with data integrity error, probably this is a bad
+			 * PEB, bit it is not marked as bad yet. This may also
+			 * be a result of power cut during erasure.
+			 */
+			si->maybe_bad_peb_count += 1;
 	case UBI_IO_BAD_HDR:
 	case UBI_IO_FF_BITFLIPS:
-		err = add_corrupted(si, pnum, ec);
+		err = add_to_list(si, pnum, ec, 1, &si->erase);
 		if (err)
 			return err;
 		goto adjust_mean_ec;
 	case UBI_IO_FF:
 		if (ec_err)
-			err = add_corrupted(si, pnum, ec);
+			err = add_to_list(si, pnum, ec, 1, &si->erase);
 		else
-			err = add_to_list(si, pnum, ec, &si->free);
+			err = add_to_list(si, pnum, ec, 0, &si->free);
 		if (err)
 			return err;
 		goto adjust_mean_ec;
@@ -885,7 +911,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
 		case UBI_COMPAT_DELETE:
 			ubi_msg("\"delete\" compatible internal volume %d:%d"
 				" found, will remove it", vol_id, lnum);
-			err = add_to_list(si, pnum, ec, &si->erase);
+			err = add_to_list(si, pnum, ec, 1, &si->erase);
 			if (err)
 				return err;
 			return 0;
@@ -900,7 +926,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
 		case UBI_COMPAT_PRESERVE:
 			ubi_msg("\"preserve\" compatible internal volume %d:%d"
 				" found", vol_id, lnum);
-			err = add_to_list(si, pnum, ec, &si->alien);
+			err = add_to_list(si, pnum, ec, 0, &si->alien);
 			if (err)
 				return err;
 			return 0;
@@ -946,19 +972,20 @@ adjust_mean_ec:
 static int check_what_we_have(struct ubi_device *ubi, struct ubi_scan_info *si)
 {
 	struct ubi_scan_leb *seb;
-	int max_corr;
+	int max_corr, peb_count;
 
-	max_corr = ubi->peb_count - si->bad_peb_count - si->alien_peb_count;
-	max_corr = max_corr / 20 ?: 8;
+	peb_count = ubi->peb_count - si->bad_peb_count - si->alien_peb_count;
+	max_corr = peb_count / 20 ?: 8;
 
 	/*
-	 * Few corrupted PEBs are not a problem and may be just a result of
+	 * Few corrupted PEBs is not a problem and may be just a result of
 	 * unclean reboots. However, many of them may indicate some problems
 	 * with the flash HW or driver.
 	 */
-	if (si->corr_peb_count >= 8) {
-		ubi_warn("%d PEBs are corrupted", si->corr_peb_count);
-		printk(KERN_WARNING "corrupted PEBs are:");
+	if (si->corr_peb_count) {
+		ubi_err("%d PEBs are corrupted and preserved",
+			si->corr_peb_count);
+		printk(KERN_ERR "Corrupted PEBs are:");
 		list_for_each_entry(seb, &si->corr, u.list)
 			printk(KERN_CONT " %d", seb->pnum);
 		printk(KERN_CONT "\n");
@@ -973,41 +1000,35 @@ static int check_what_we_have(struct ubi_device *ubi, struct ubi_scan_info *si)
 		}
 	}
 
-	if (si->free_peb_count + si->used_peb_count +
-	    si->alien_peb_count == 0) {
-		/* No UBI-formatted eraseblocks were found */
-		if (si->corr_peb_count == si->read_err_count &&
-		    si->corr_peb_count < 8) {
-			/* No or just few corrupted PEBs, and all of them had a
-			 * read error. We assume that those are bad PEBs, which
-			 * were just not marked as bad so far.
-			 *
-			 * This piece of code basically tries to distinguish
-			 * between the following 2 situations:
-			 *
-			 * 1. Flash is empty, but there are few bad PEBs, which
-			 *    are not marked as bad so far, and which were read
-			 *    with error. We want to go ahead and format this
-			 *    flash. While formating, the faulty PEBs will
-			 *    probably be marked as bad.
-			 *
-			 * 2. Flash probably contains non-UBI data and we do
-			 * not want to format it and destroy possibly needed
-			 * data (e.g., consider the case when the bootloader
-			 * MTD partition was accidentally fed to UBI).
-			 */
+	if (si->empty_peb_count + si->maybe_bad_peb_count == peb_count) {
+		/*
+		 * All PEBs are empty, or almost all - a couple PEBs look like
+		 * they may be bad PEBs which were not marked as bad yet.
+		 *
+		 * This piece of code basically tries to distinguish between
+		 * the following situations:
+		 *
+		 * 1. Flash is empty, but there are few bad PEBs, which are not
+		 *    marked as bad so far, and which were read with error. We
+		 *    want to go ahead and format this flash. While formatting,
+		 *    the faulty PEBs will probably be marked as bad.
+		 *
+		 * 2. Flash contains non-UBI data and we do not want to format
+		 *    it and destroy possibly important information.
+		 */
+		if (si->maybe_bad_peb_count <= 2) {
 			si->is_empty = 1;
 			ubi_msg("empty MTD device detected");
-			get_random_bytes(&ubi->image_seq, sizeof(ubi->image_seq));
+			get_random_bytes(&ubi->image_seq,
+					 sizeof(ubi->image_seq));
 		} else {
-			ubi_err("MTD device possibly contains non-UBI data, "
-				"refusing it");
+			ubi_err("MTD device is not UBI-formatted and possibly "
+				"contains non-UBI data - refusing it");
 			return -EINVAL;
 		}
+
 	}
 
-	if (si->corr_peb_count > 0)
-		ubi_msg("corrupted PEBs will be formatted");
 	return 0;
 }