Merge branch 'linux-next' of git://git.infradead.org/ubi-2.6

* 'linux-next' of git://git.infradead.org/ubi-2.6:
  UBI: tighten the corrupted PEB criteria
  UBI: fix check_data_ff return code
  UBI: remember copy_flag while scanning
  UBI: preserve corrupted PEBs
  UBI: add truly corrupted PEBs to corrupted list
  UBI: introduce debugging helper function
  UBI: make check_pattern function non-static
  UBI: do not put eraseblocks to the corrupted list unnecessarily
  UBI: separate out corrupted list
  UBI: change cascade of ifs to switch statements
  UBI: rename a local variable
  UBI: handle bit-flips when no header found
  UBI: remove duplicate IO error codes
  UBI: rename IO error code
  UBI: fix small 80 characters limit style issue
  UBI: cleanup and simplify Kconfig

13 files changed, 419 insertions, 286 deletions

diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index f702a163d8d..3cf193fb5e0 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -1,9 +1,5 @@
-menu "UBI - Unsorted block images"
-	depends on MTD
-
-config MTD_UBI
-	tristate "Enable UBI"
-	depends on MTD
+menuconfig MTD_UBI
+	tristate "Enable UBI - Unsorted block images"
 	select CRC32
 	help
 	  UBI is a software layer above MTD layer which admits of LVM-like
@@ -12,11 +8,12 @@ config MTD_UBI
 	  capabilities. Please, consult the MTD web site for more details
 	  (www.linux-mtd.infradead.org).
 
+if MTD_UBI
+
 config MTD_UBI_WL_THRESHOLD
 	int "UBI wear-leveling threshold"
 	default 4096
 	range 2 65536
-	depends on MTD_UBI
 	help
 	  This parameter defines the maximum difference between the highest
 	  erase counter value and the lowest erase counter value of eraseblocks
@@ -34,7 +31,6 @@ config MTD_UBI_BEB_RESERVE
 	int "Percentage of reserved eraseblocks for bad eraseblocks handling"
 	default 1
 	range 0 25
-	depends on MTD_UBI
 	help
 	  If the MTD device admits of bad eraseblocks (e.g. NAND flash), UBI
 	  reserves some amount of physical eraseblocks to handle new bad
@@ -48,8 +44,6 @@ config MTD_UBI_BEB_RESERVE
 
 config MTD_UBI_GLUEBI
 	tristate "MTD devices emulation driver (gluebi)"
-	default n
-	depends on MTD_UBI
 	help
 	   This option enables gluebi - an additional driver which emulates MTD
 	   devices on top of UBI volumes: for each UBI volumes an MTD device is
@@ -59,4 +53,5 @@ config MTD_UBI_GLUEBI
 	   software.
 
 source "drivers/mtd/ubi/Kconfig.debug"
-endmenu
+
+endif # MTD_UBI
diff --git a/drivers/mtd/ubi/Kconfig.debug b/drivers/mtd/ubi/Kconfig.debug
index 61f6e5e4045..fad4adc0fe2 100644
--- a/drivers/mtd/ubi/Kconfig.debug
+++ b/drivers/mtd/ubi/Kconfig.debug
@@ -1,94 +1,73 @@
 comment "UBI debugging options"
-	depends on MTD_UBI
 
 config MTD_UBI_DEBUG
 	bool "UBI debugging"
 	depends on SYSFS
-	depends on MTD_UBI
 	select DEBUG_FS
 	select KALLSYMS_ALL if KALLSYMS && DEBUG_KERNEL
 	help
 	  This option enables UBI debugging.
 
+if MTD_UBI_DEBUG
+
 config MTD_UBI_DEBUG_MSG
 	bool "UBI debugging messages"
-	depends on MTD_UBI_DEBUG
-	default n
 	help
 	  This option enables UBI debugging messages.
 
 config MTD_UBI_DEBUG_PARANOID
 	bool "Extra self-checks"
-	default n
-	depends on MTD_UBI_DEBUG
 	help
 	  This option enables extra checks in UBI code. Note this slows UBI down
 	  significantly.
 
 config MTD_UBI_DEBUG_DISABLE_BGT
 	bool "Do not enable the UBI background thread"
-	depends on MTD_UBI_DEBUG
-	default n
 	help
 	  This option switches the background thread off by default. The thread
 	  may be also be enabled/disabled via UBI sysfs.
 
 config MTD_UBI_DEBUG_EMULATE_BITFLIPS
 	bool "Emulate flash bit-flips"
-	depends on MTD_UBI_DEBUG
-	default n
 	help
 	  This option emulates bit-flips with probability 1/50, which in turn
 	  causes scrubbing. Useful for debugging and stressing UBI.
 
 config MTD_UBI_DEBUG_EMULATE_WRITE_FAILURES
 	bool "Emulate flash write failures"
-	depends on MTD_UBI_DEBUG
-	default n
 	help
 	  This option emulates write failures with probability 1/100. Useful for
 	  debugging and testing how UBI handlines errors.
 
 config MTD_UBI_DEBUG_EMULATE_ERASE_FAILURES
 	bool "Emulate flash erase failures"
-	depends on MTD_UBI_DEBUG
-	default n
 	help
 	  This option emulates erase failures with probability 1/100. Useful for
 	  debugging and testing how UBI handlines errors.
 
-menu "Additional UBI debugging messages"
-	depends on MTD_UBI_DEBUG
+comment "Additional UBI debugging messages"
 
 config MTD_UBI_DEBUG_MSG_BLD
 	bool "Additional UBI initialization and build messages"
-	default n
-	depends on MTD_UBI_DEBUG
 	help
 	  This option enables detailed UBI initialization and device build
 	  debugging messages.
 
 config MTD_UBI_DEBUG_MSG_EBA
 	bool "Eraseblock association unit messages"
-	default n
-	depends on MTD_UBI_DEBUG
 	help
 	  This option enables debugging messages from the UBI eraseblock
 	  association unit.
 
 config MTD_UBI_DEBUG_MSG_WL
 	bool "Wear-leveling unit messages"
-	default n
-	depends on MTD_UBI_DEBUG
 	help
 	  This option enables debugging messages from the UBI wear-leveling
 	  unit.
 
 config MTD_UBI_DEBUG_MSG_IO
 	bool "Input/output unit messages"
-	default n
-	depends on MTD_UBI_DEBUG
 	help
 	  This option enables debugging messages from the UBI input/output unit.
 
-endmenu # UBI debugging messages
+endif # MTD_UBI_DEBUG
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 78ae89488a4..5ebe280225d 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -95,8 +95,8 @@ DEFINE_MUTEX(ubi_devices_mutex);
 static DEFINE_SPINLOCK(ubi_devices_lock);
 
 /* "Show" method for files in '/<sysfs>/class/ubi/' */
-static ssize_t ubi_version_show(struct class *class, struct class_attribute *attr,
-				char *buf)
+static ssize_t ubi_version_show(struct class *class,
+				struct class_attribute *attr, char *buf)
 {
 	return sprintf(buf, "%d\n", UBI_VERSION);
 }
@@ -591,6 +591,7 @@ static int attach_by_scanning(struct ubi_device *ubi)
 
 	ubi->bad_peb_count = si->bad_peb_count;
 	ubi->good_peb_count = ubi->peb_count - ubi->bad_peb_count;
+	ubi->corr_peb_count = si->corr_peb_count;
 	ubi->max_ec = si->max_ec;
 	ubi->mean_ec = si->mean_ec;
 	ubi_msg("max. sequence number:       %llu", si->max_sqnum);
@@ -972,6 +973,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 	ubi_msg("MTD device size:            %llu MiB", ubi->flash_size >> 20);
 	ubi_msg("number of good PEBs:        %d", ubi->good_peb_count);
 	ubi_msg("number of bad PEBs:         %d", ubi->bad_peb_count);
+	ubi_msg("number of corrupted PEBs:   %d", ubi->corr_peb_count);
 	ubi_msg("max. allowed volumes:       %d", ubi->vtbl_slots);
 	ubi_msg("wear-leveling threshold:    %d", CONFIG_MTD_UBI_WL_THRESHOLD);
 	ubi_msg("number of internal volumes: %d", UBI_INT_VOL_COUNT);
diff --git a/drivers/mtd/ubi/debug.h b/drivers/mtd/ubi/debug.h
index 17a10712972..9eca95074bc 100644
--- a/drivers/mtd/ubi/debug.h
+++ b/drivers/mtd/ubi/debug.h
@@ -57,6 +57,9 @@ void ubi_dbg_dump_seb(const struct ubi_scan_leb *seb, int type);
 void ubi_dbg_dump_mkvol_req(const struct ubi_mkvol_req *req);
 void ubi_dbg_dump_flash(struct ubi_device *ubi, int pnum, int offset, int len);
 
+#define ubi_dbg_print_hex_dump(l, ps, pt, r, g, b, len, a)  \
+		print_hex_dump(l, ps, pt, r, g, b, len, a)
+
 #ifdef CONFIG_MTD_UBI_DEBUG_MSG
 /* General debugging messages */
 #define dbg_gen(fmt, ...) dbg_msg(fmt, ##__VA_ARGS__)
@@ -172,6 +175,7 @@ static inline int ubi_dbg_is_erase_failure(void)
 #define ubi_dbg_dump_seb(seb, type)      ({})
 #define ubi_dbg_dump_mkvol_req(req)      ({})
 #define ubi_dbg_dump_flash(ubi, pnum, offset, len) ({})
+#define ubi_dbg_print_hex_dump(l, ps, pt, r, g, b, len, a)  ({})
 
 #define UBI_IO_DEBUG               0
 #define DBG_DISABLE_BGT            0
diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index fe74749e0da..4be67181501 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -418,7 +418,7 @@ retry:
 				 * may try to recover data. FIXME: but this is
 				 * not implemented.
 				 */
-				if (err == UBI_IO_BAD_HDR_READ ||
+				if (err == UBI_IO_BAD_HDR_EBADMSG ||
 				    err == UBI_IO_BAD_HDR) {
 					ubi_warn("corrupted VID header at PEB "
 						 "%d, LEB %d:%d", pnum, vol_id,
@@ -963,7 +963,7 @@ write_error:
 static int is_error_sane(int err)
 {
 	if (err == -EIO || err == -ENOMEM || err == UBI_IO_BAD_HDR ||
-	    err == UBI_IO_BAD_HDR_READ || err == -ETIMEDOUT)
+	    err == UBI_IO_BAD_HDR_EBADMSG || err == -ETIMEDOUT)
 		return 0;
 	return 1;
 }
@@ -1201,6 +1201,9 @@ static void print_rsvd_warning(struct ubi_device *ubi,
 
 	ubi_warn("cannot reserve enough PEBs for bad PEB handling, reserved %d,"
 		 " need %d", ubi->beb_rsvd_pebs, ubi->beb_rsvd_level);
+	if (ubi->corr_peb_count)
+		ubi_warn("%d PEBs are corrupted and not used",
+			ubi->corr_peb_count);
 }
 
 /**
@@ -1263,6 +1266,9 @@ int ubi_eba_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
 	if (ubi->avail_pebs < EBA_RESERVED_PEBS) {
 		ubi_err("no enough physical eraseblocks (%d, need %d)",
 			ubi->avail_pebs, EBA_RESERVED_PEBS);
+		if (ubi->corr_peb_count)
+			ubi_err("%d PEBs are corrupted and not used",
+				ubi->corr_peb_count);
 		err = -ENOSPC;
 		goto out_free;
 	}
diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
index 332f992f13d..c2960ac9f39 100644
--- a/drivers/mtd/ubi/io.c
+++ b/drivers/mtd/ubi/io.c
@@ -376,25 +376,6 @@ retry:
 	return 0;
 }
 
-/**
- * check_pattern - check if buffer contains only a certain byte pattern.
- * @buf: buffer to check
- * @patt: the pattern to check
- * @size: buffer size in bytes
- *
- * This function returns %1 in there are only @patt bytes in @buf, and %0 if
- * something else was also found.
- */
-static int check_pattern(const void *buf, uint8_t patt, int size)
-{
-	int i;
-
-	for (i = 0; i < size; i++)
-		if (((const uint8_t *)buf)[i] != patt)
-			return 0;
-	return 1;
-}
-
 /* Patterns to write to a physical eraseblock when torturing it */
 static uint8_t patterns[] = {0xa5, 0x5a, 0x0};
 
@@ -426,7 +407,7 @@ static int torture_peb(struct ubi_device *ubi, int pnum)
 		if (err)
 			goto out;
 
-		err = check_pattern(ubi->peb_buf1, 0xFF, ubi->peb_size);
+		err = ubi_check_pattern(ubi->peb_buf1, 0xFF, ubi->peb_size);
 		if (err == 0) {
 			ubi_err("erased PEB %d, but a non-0xFF byte found",
 				pnum);
@@ -445,7 +426,8 @@ static int torture_peb(struct ubi_device *ubi, int pnum)
 		if (err)
 			goto out;
 
-		err = check_pattern(ubi->peb_buf1, patterns[i], ubi->peb_size);
+		err = ubi_check_pattern(ubi->peb_buf1, patterns[i],
+					ubi->peb_size);
 		if (err == 0) {
 			ubi_err("pattern %x checking failed for PEB %d",
 				patterns[i], pnum);
@@ -517,7 +499,7 @@ static int nor_erase_prepare(struct ubi_device *ubi, int pnum)
 	 * In this case we probably anyway have garbage in this PEB.
 	 */
 	err1 = ubi_io_read_vid_hdr(ubi, pnum, &vid_hdr, 0);
-	if (err1 == UBI_IO_BAD_HDR_READ || err1 == UBI_IO_BAD_HDR)
+	if (err1 == UBI_IO_BAD_HDR_EBADMSG || err1 == UBI_IO_BAD_HDR)
 		/*
 		 * The VID header is corrupted, so we can safely erase this
 		 * PEB and not afraid that it will be treated as a valid PEB in
@@ -712,47 +694,47 @@ bad:
  *   and corrected by the flash driver; this is harmless but may indicate that
  *   this eraseblock may become bad soon (but may be not);
  * o %UBI_IO_BAD_HDR if the erase counter header is corrupted (a CRC error);
- * o %UBI_IO_PEB_EMPTY if the physical eraseblock is empty;
+ * o %UBI_IO_BAD_HDR_EBADMSG is the same as %UBI_IO_BAD_HDR, but there also was
+ *   a data integrity error (uncorrectable ECC error in case of NAND);
+ * o %UBI_IO_FF if only 0xFF bytes were read (the PEB is supposedly empty)
  * o a negative error code in case of failure.
  */
 int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
 		       struct ubi_ec_hdr *ec_hdr, int verbose)
 {
-	int err, read_err = 0;
+	int err, read_err;
 	uint32_t crc, magic, hdr_crc;
 
 	dbg_io("read EC header from PEB %d", pnum);
 	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
 
-	err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
-	if (err) {
-		if (err != UBI_IO_BITFLIPS && err != -EBADMSG)
-			return err;
+	read_err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
+	if (read_err) {
+		if (read_err != UBI_IO_BITFLIPS && read_err != -EBADMSG)
+			return read_err;
 
 		/*
 		 * We read all the data, but either a correctable bit-flip
-		 * occurred, or MTD reported about some data integrity error,
-		 * like an ECC error in case of NAND. The former is harmless,
-		 * the later may mean that the read data is corrupted. But we
-		 * have a CRC check-sum and we will detect this. If the EC
-		 * header is still OK, we just report this as there was a
-		 * bit-flip.
+		 * occurred, or MTD reported a data integrity error
+		 * (uncorrectable ECC error in case of NAND). The former is
+		 * harmless, the later may mean that the read data is
+		 * corrupted. But we have a CRC check-sum and we will detect
+		 * this. If the EC header is still OK, we just report this as
+		 * there was a bit-flip, to force scrubbing.
 		 */
-		if (err == -EBADMSG)
-			read_err = UBI_IO_BAD_HDR_READ;
 	}
 
 	magic = be32_to_cpu(ec_hdr->magic);
 	if (magic != UBI_EC_HDR_MAGIC) {
-		if (read_err)
-			return read_err;
+		if (read_err == -EBADMSG)
+			return UBI_IO_BAD_HDR_EBADMSG;
 
 		/*
 		 * The magic field is wrong. Let's check if we have read all
 		 * 0xFF. If yes, this physical eraseblock is assumed to be
 		 * empty.
 		 */
-		if (check_pattern(ec_hdr, 0xFF, UBI_EC_HDR_SIZE)) {
+		if (ubi_check_pattern(ec_hdr, 0xFF, UBI_EC_HDR_SIZE)) {
 			/* The physical eraseblock is supposedly empty */
 			if (verbose)
 				ubi_warn("no EC header found at PEB %d, "
@@ -760,7 +742,10 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
 			else if (UBI_IO_DEBUG)
 				dbg_msg("no EC header found at PEB %d, "
 					"only 0xFF bytes", pnum);
-			return UBI_IO_PEB_EMPTY;
+			if (!read_err)
+				return UBI_IO_FF;
+			else
+				return UBI_IO_FF_BITFLIPS;
 		}
 
 		/*
@@ -788,7 +773,11 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
 		} else if (UBI_IO_DEBUG)
 			dbg_msg("bad EC header CRC at PEB %d, calculated "
 				"%#08x, read %#08x", pnum, crc, hdr_crc);
-		return read_err ?: UBI_IO_BAD_HDR;
+
+		if (!read_err)
+			return UBI_IO_BAD_HDR;
+		else
+			return UBI_IO_BAD_HDR_EBADMSG;
 	}
 
 	/* And of course validate what has just been read from the media */
@@ -975,22 +964,16 @@ bad:
  *
  * This function reads the volume identifier header from physical eraseblock
  * @pnum and stores it in @vid_hdr. It also checks CRC checksum of the read
- * volume identifier header. The following codes may be returned:
+ * volume identifier header. The error codes are the same as in
+ * 'ubi_io_read_ec_hdr()'.
  *
- * o %0 if the CRC checksum is correct and the header was successfully read;
- * o %UBI_IO_BITFLIPS if the CRC is correct, but bit-flips were detected
- *   and corrected by the flash driver; this is harmless but may indicate that
- *   this eraseblock may become bad soon;
- * o %UBI_IO_BAD_HDR if the volume identifier header is corrupted (a CRC
- *   error detected);
- * o %UBI_IO_PEB_FREE if the physical eraseblock is free (i.e., there is no VID
- *   header there);
- * o a negative error code in case of failure.
+ * Note, the implementation of this function is also very similar to
+ * 'ubi_io_read_ec_hdr()', so refer commentaries in 'ubi_io_read_ec_hdr()'.
  */
 int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
 			struct ubi_vid_hdr *vid_hdr, int verbose)
 {
-	int err, read_err = 0;
+	int err, read_err;
 	uint32_t crc, magic, hdr_crc;
 	void *p;
 
@@ -998,48 +981,29 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
 	ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);
 
 	p = (char *)vid_hdr - ubi->vid_hdr_shift;
-	err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
+	read_err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
 			  ubi->vid_hdr_alsize);
-	if (err) {
-		if (err != UBI_IO_BITFLIPS && err != -EBADMSG)
-			return err;
-
-		/*
-		 * We read all the data, but either a correctable bit-flip
-		 * occurred, or MTD reported about some data integrity error,
-		 * like an ECC error in case of NAND. The former is harmless,
-		 * the later may mean the read data is corrupted. But we have a
-		 * CRC check-sum and we will identify this. If the VID header is
-		 * still OK, we just report this as there was a bit-flip.
-		 */
-		if (err == -EBADMSG)
-			read_err = UBI_IO_BAD_HDR_READ;
-	}
+	if (read_err && read_err != UBI_IO_BITFLIPS && read_err != -EBADMSG)
+		return read_err;
 
 	magic = be32_to_cpu(vid_hdr->magic);
 	if (magic != UBI_VID_HDR_MAGIC) {
-		if (read_err)
-			return read_err;
+		if (read_err == -EBADMSG)
+			return UBI_IO_BAD_HDR_EBADMSG;
 
-		/*
-		 * If we have read all 0xFF bytes, the VID header probably does
-		 * not exist and the physical eraseblock is assumed to be free.
-		 */
-		if (check_pattern(vid_hdr, 0xFF, UBI_VID_HDR_SIZE)) {
-			/* The physical eraseblock is supposedly free */
+		if (ubi_check_pattern(vid_hdr, 0xFF, UBI_VID_HDR_SIZE)) {
 			if (verbose)
 				ubi_warn("no VID header found at PEB %d, "
 					 "only 0xFF bytes", pnum);
 			else if (UBI_IO_DEBUG)
 				dbg_msg("no VID header found at PEB %d, "
 					"only 0xFF bytes", pnum);
-			return UBI_IO_PEB_FREE;
+			if (!read_err)
+				return UBI_IO_FF;
+			else
+				return UBI_IO_FF_BITFLIPS;
 		}
 
-		/*
-		 * This is not a valid VID header, and these are not 0xFF
-		 * bytes. Report that the header is corrupted.
-		 */
 		if (verbose) {
 			ubi_warn("bad magic number at PEB %d: %08x instead of "
 				 "%08x", pnum, magic, UBI_VID_HDR_MAGIC);
@@ -1061,20 +1025,18 @@ int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
 		} else if (UBI_IO_DEBUG)
 			dbg_msg("bad CRC at PEB %d, calculated %#08x, "
 				"read %#08x", pnum, crc, hdr_crc);
-		return read_err ?: UBI_IO_BAD_HDR;
+		if (!read_err)
+			return UBI_IO_BAD_HDR;
+		else
+			return UBI_IO_BAD_HDR_EBADMSG;
 	}
 
-	/* Validate the VID header that we have just read */
 	err = validate_vid_hdr(ubi, vid_hdr);
 	if (err) {
 		ubi_err("validation failed for PEB %d", pnum);
 		return -EINVAL;
 	}
 
-	/*
-	 * If there was a read error (%-EBADMSG), but the header CRC is still
-	 * OK, report about a bit-flip to force scrubbing on this PEB.
-	 */
 	return read_err ? UBI_IO_BITFLIPS : 0;
 }
 
@@ -1383,7 +1345,7 @@ int ubi_dbg_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len)
 		goto error;
 	}
 
-	err = check_pattern(ubi->dbg_peb_buf, 0xFF, len);
+	err = ubi_check_pattern(ubi->dbg_peb_buf, 0xFF, len);
 	if (err == 0) {
 		ubi_err("flash region at PEB %d:%d, length %d does not "
 			"contain all 0xFF bytes", pnum, offset, len);
diff --git a/drivers/mtd/ubi/misc.c b/drivers/mtd/ubi/misc.c
index 22ad3140294..ff2a65c37f6 100644
--- a/drivers/mtd/ubi/misc.c
+++ b/drivers/mtd/ubi/misc.c
@@ -103,3 +103,22 @@ void ubi_calculate_reserved(struct ubi_device *ubi)
 	if (ubi->beb_rsvd_level < MIN_RESEVED_PEBS)
 		ubi->beb_rsvd_level = MIN_RESEVED_PEBS;
 }
+
+/**
+ * ubi_check_pattern - check if buffer contains only a certain byte pattern.
+ * @buf: buffer to check
+ * @patt: the pattern to check
+ * @size: buffer size in bytes
+ *
+ * This function returns %1 in there are only @patt bytes in @buf, and %0 if
+ * something else was also found.
+ */
+int ubi_check_pattern(const void *buf, uint8_t patt, int size)
+{
+	int i;
+
+	for (i = 0; i < size; i++)
+		if (((const uint8_t *)buf)[i] != patt)
+			return 0;
+	return 1;
+}
diff --git a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c
index 69b52e9c948..3c631863bf4 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 +38,33 @@
  * 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 (e.g., UBIFS) 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.
+ *
+ * However, it is difficult to reliably distinguish between these types of
+ * corruptions and UBI's strategy is as follows. UBI assumes (2.) if the VID
+ * header is corrupted and the data area does not contain all 0xFFs, and there
+ * were not bit-flips or integrity errors while reading the data area. Otherwise
+ * UBI assumes (1.). The assumptions are:
+ *   o if the data area contains only 0xFFs, there is no data, and it is safe
+ *     to just erase this PEB.
+ *   o if the data area has bit-flips and data integrity errors (ECC errors on
+ *     NAND), it is probably a PEB which was being erased when power cut
+ *     happened.
  */
 
 #include <linux/err.h>
@@ -62,26 +89,26 @@ 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, corrupted or
- * alien lists. Returns zero in case of success and a negative error code in
- * case of failure.
+ * This function adds physical eraseblock @pnum to free, erase, or alien lists.
+ * 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->corr) {
-		dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);
-		si->corr_peb_count += 1;
 	} else if (list == &si->alien) {
 		dbg_bld("add to alien: PEB %d, EC %d", pnum, ec);
 		si->alien_peb_count += 1;
@@ -94,7 +121,37 @@ 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;
+}
+
+/**
+ * add_corrupted - add a corrupted physical eraseblock.
+ * @si: scanning information
+ * @pnum: physical eraseblock number to add
+ * @ec: erase counter of the physical eraseblock
+ *
+ * This function adds corrupted physical eraseblock @pnum to the 'corr' list.
+ * The corruption was presumably not caused by a power cut. Returns zero in
+ * case of success and a negative error code in case of failure.
+ */
+static int add_corrupted(struct ubi_scan_info *si, int pnum, int ec)
+{
+	struct ubi_scan_leb *seb;
+
+	dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);
+
+	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
+	if (!seb)
+		return -ENOMEM;
+
+	si->corr_peb_count += 1;
+	seb->pnum = pnum;
+	seb->ec = ec;
+	list_add(&seb->u.list, &si->corr);
 	return 0;
 }
 
@@ -258,8 +315,8 @@ 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;
@@ -285,19 +342,25 @@ static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
 			return 1;
 		}
 	} else {
-		pnum = seb->pnum;
+		if (!seb->copy_flag) {
+			/* It is not a copy, so it is newer */
+			dbg_bld("first PEB %d is newer, copy_flag is unset",
+				pnum);
+			return bitflips << 1;
+		}
 
 		vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
 		if (!vh)
 			return -ENOMEM;
 
+		pnum = seb->pnum;
 		err = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);
 		if (err) {
 			if (err == UBI_IO_BITFLIPS)
 				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;
 
@@ -305,14 +368,6 @@ static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
 			}
 		}
 
-		if (!vh->copy_flag) {
-			/* It is not a copy, so it is newer */
-			dbg_bld("first PEB %d is newer, copy_flag is unset",
-				pnum);
-			err = bitflips << 1;
-			goto out_free_vidh;
-		}
-
 		vid_hdr = vh;
 	}
 
@@ -463,18 +518,15 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 			if (err)
 				return err;
 
-			if (cmp_res & 4)
-				err = add_to_list(si, seb->pnum, seb->ec,
-						  &si->corr);
-			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;
 
 			seb->ec = ec;
 			seb->pnum = pnum;
 			seb->scrub = ((cmp_res & 2) || bitflips);
+			seb->copy_flag = vid_hdr->copy_flag;
 			seb->sqnum = sqnum;
 
 			if (sv->highest_lnum == lnum)
@@ -487,10 +539,8 @@ 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_to_list(si, pnum, ec, &si->corr);
-			else
-				return add_to_list(si, pnum, ec, &si->erase);
+			return add_to_list(si, pnum, ec, cmp_res & 4,
+					   &si->erase);
 		}
 	}
 
@@ -510,8 +560,9 @@ int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
 	seb->ec = ec;
 	seb->pnum = pnum;
 	seb->lnum = lnum;
-	seb->sqnum = sqnum;
 	seb->scrub = bitflips;
+	seb->copy_flag = vid_hdr->copy_flag;
+	seb->sqnum = sqnum;
 
 	if (sv->highest_lnum <= lnum) {
 		sv->highest_lnum = lnum;
@@ -521,7 +572,6 @@ 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;
 }
 
@@ -668,8 +718,8 @@ out_free:
 struct ubi_scan_leb *ubi_scan_get_free_peb(struct ubi_device *ubi,
 					   struct ubi_scan_info *si)
 {
-	int err = 0, i;
-	struct ubi_scan_leb *seb;
+	int err = 0;
+	struct ubi_scan_leb *seb, *tmp_seb;
 
 	if (!list_empty(&si->free)) {
 		seb = list_entry(si->free.next, struct ubi_scan_leb, u.list);
@@ -678,38 +728,86 @@ struct ubi_scan_leb *ubi_scan_get_free_peb(struct ubi_device *ubi,
 		return seb;
 	}
 
-	for (i = 0; i < 2; i++) {
-		struct list_head *head;
-		struct ubi_scan_leb *tmp_seb;
+	/*
+	 * We try to erase the first physical eraseblock from the erase list
+	 * and pick it if we succeed, or try to erase the next one if not. And
+	 * so forth. We don't want to take care about bad eraseblocks here -
+	 * they'll be handled later.
+	 */
+	list_for_each_entry_safe(seb, tmp_seb, &si->erase, u.list) {
+		if (seb->ec == UBI_SCAN_UNKNOWN_EC)
+			seb->ec = si->mean_ec;
 
-		if (i == 0)
-			head = &si->erase;
-		else
-			head = &si->corr;
+		err = ubi_scan_erase_peb(ubi, si, seb->pnum, seb->ec+1);
+		if (err)
+			continue;
 
+		seb->ec += 1;
+		list_del(&seb->u.list);
+		dbg_bld("return PEB %d, EC %d", seb->pnum, seb->ec);
+		return seb;
+	}
+
+	ubi_err("no free eraseblocks");
+	return ERR_PTR(-ENOSPC);
+}
+
+/**
+ * check_corruption - check the data area of PEB.
+ * @ubi: UBI device description object
+ * @vid_hrd: the (corrupted) VID header of this PEB
+ * @pnum: the physical eraseblock number to check
+ *
+ * This is a helper function which is used to distinguish between VID header
+ * corruptions caused by power cuts and other reasons. If the PEB contains only
+ * 0xFF bytes in the data area, the VID header is most probably corrupted
+ * because of a power cut (%0 is returned in this case). Otherwise, it was
+ * probably corrupted for some other reasons (%1 is returned in this case). A
+ * negative error code is returned if a read error occurred.
+ *
+ * If the corruption reason was a power cut, UBI can safely erase this PEB.
+ * Otherwise, it should preserve it to avoid possibly destroying important
+ * information.
+ */
+static int check_corruption(struct ubi_device *ubi, struct ubi_vid_hdr *vid_hdr,
+			    int pnum)
+{
+	int err;
+
+	mutex_lock(&ubi->buf_mutex);
+	memset(ubi->peb_buf1, 0x00, ubi->leb_size);
+
+	err = ubi_io_read(ubi, ubi->peb_buf1, pnum, ubi->leb_start,
+			  ubi->leb_size);
+	if (err == UBI_IO_BITFLIPS || err == -EBADMSG) {
 		/*
-		 * We try to erase the first physical eraseblock from the @head
-		 * list and pick it if we succeed, or try to erase the
-		 * next one if not. And so forth. We don't want to take care
-		 * about bad eraseblocks here - they'll be handled later.
+		 * Bit-flips or integrity errors while reading the data area.
+		 * It is difficult to say for sure what type of corruption is
+		 * this, but presumably a power cut happened while this PEB was
+		 * erased, so it became unstable and corrupted, and should be
+		 * erased.
 		 */
-		list_for_each_entry_safe(seb, tmp_seb, head, u.list) {
-			if (seb->ec == UBI_SCAN_UNKNOWN_EC)
-				seb->ec = si->mean_ec;
+		return 0;
+	}
 
-			err = ubi_scan_erase_peb(ubi, si, seb->pnum, seb->ec+1);
-			if (err)
-				continue;
+	if (err)
+		return err;
 
-			seb->ec += 1;
-			list_del(&seb->u.list);
-			dbg_bld("return PEB %d, EC %d", seb->pnum, seb->ec);
-			return seb;
-		}
+	if (ubi_check_pattern(ubi->peb_buf1, 0xFF, ubi->leb_size)) {
+		mutex_unlock(&ubi->buf_mutex);
+		return 0;
 	}
 
-	ubi_err("no eraseblocks found");
-	return ERR_PTR(-ENOSPC);
+	ubi_err("PEB %d contains corrupted VID header, and the data does not "
+		"contain all 0xFF, this may be a non-UBI PEB or a severe VID "
+		"header corruption which requires manual inspection", pnum);
+	ubi_dbg_dump_vid_hdr(vid_hdr);
+	dbg_msg("hexdump of PEB %d offset %d, length %d",
+		pnum, ubi->leb_start, ubi->leb_size);
+	ubi_dbg_print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
+			       ubi->peb_buf1, ubi->leb_size, 1);
+	mutex_unlock(&ubi->buf_mutex);
+	return 1;
 }
 
 /**
@@ -725,7 +823,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
 		      int pnum)
 {
 	long long uninitialized_var(ec);
-	int err, bitflips = 0