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 f702a163d8df..3cf193fb5e00 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 61f6e5e40458..fad4adc0fe2c 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 78ae89488a4f..5ebe280225d6 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 17a107129726..9eca95074bc2 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 fe74749e0dae..4be671815014 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 332f992f13d9..c2960ac9f39c 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 22ad31402945..ff2a65c37f69 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 69b52e9c9489..3c631863bf40 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, vol_id, ec_corr = 0;
+        int err, bitflips = 0, vol_id, ec_err = 0;
 
         dbg_bld("scan PEB %d", pnum);
 
@@ -746,22 +844,37 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
         err = ubi_io_read_ec_hdr(ubi, pnum, ech, 0);
         if (err < 0)
                 return err;
-        else if (err == UBI_IO_BITFLIPS)
+        switch (err) {
+        case 0:
+                break;
+        case UBI_IO_BITFLIPS:
                 bitflips = 1;
-        else if (err == UBI_IO_PEB_EMPTY)
-                return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, &si->erase);
-        else if (err == UBI_IO_BAD_HDR_READ || err == UBI_IO_BAD_HDR) {
+                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:
+                si->empty_peb_count += 1;
+                return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, 1,
+                                   &si->erase);
+        case UBI_IO_BAD_HDR_EBADMSG:
+        case UBI_IO_BAD_HDR:
                 /*
                  * We have to also look at the VID header, possibly it is not
                  * corrupted. Set %bitflips flag in order to make this PEB be
                  * moved and EC be re-created.
                  */
-                ec_corr = err;
+                ec_err = err;
                 ec = UBI_SCAN_UNKNOWN_EC;
                 bitflips = 1;
+                break;
+        default:
+                ubi_err("'ubi_io_read_ec_hdr()' returned unknown code %d", err);
+                return -EINVAL;
         }
 
-        if (!ec_corr) {
+        if (!ec_err) {
                 int image_seq;
 
                 /* Make sure UBI version is OK */
@@ -814,24 +927,67 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
         err = ubi_io_read_vid_hdr(ubi, pnum, vidh, 0);
         if (err < 0)
                 return err;
-        else if (err == UBI_IO_BITFLIPS)
+        switch (err) {
+        case 0:
+                break;
+        case UBI_IO_BITFLIPS:
                 bitflips = 1;
-        else if (err == UBI_IO_BAD_HDR_READ || err == UBI_IO_BAD_HDR ||
-                 (err == UBI_IO_PEB_FREE && ec_corr)) {
-                /* VID header is corrupted */
-                if (err == UBI_IO_BAD_HDR_READ ||
-                    ec_corr == UBI_IO_BAD_HDR_READ)
-                        si->read_err_count += 1;
-                err = add_to_list(si, pnum, ec, &si->corr);
+                break;
+        case UBI_IO_BAD_HDR_EBADMSG:
+                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:
+                if (ec_err)
+                        /*
+                         * Both headers are corrupted. There is a possibility
+                         * that this a valid UBI PEB which has corresponding
+                         * LEB, but the headers are corrupted. However, it is
+                         * impossible to distinguish it from a PEB which just
+                         * contains garbage because of a power cut during erase
+                         * operation. So we just schedule this PEB for erasure.
+                         */
+                        err = 0;
+                else
+                        /*
+                         * The EC was OK, but the VID header is corrupted. We
+                         * have to check what is in the data area.
+                         */
+                        err = check_corruption(ubi, vidh, pnum);
+
+                if (err < 0)
+                        return err;
+                else if (!err)
+                        /* This corruption is caused by a power cut */
+                        err = add_to_list(si, pnum, ec, 1, &si->erase);
+                else
+                        /* This is an unexpected corruption */
+                        err = add_corrupted(si, pnum, ec);
                 if (err)
                         return err;
                 goto adjust_mean_ec;
-        } else if (err == UBI_IO_PEB_FREE) {
-                /* No VID header - the physical eraseblock is free */
-                err = add_to_list(si, pnum, ec, &si->free);
+        case UBI_IO_FF_BITFLIPS:
+                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_to_list(si, pnum, ec, 1, &si->erase);
+                else
+                        err = add_to_list(si, pnum, ec, 0, &si->free);
+                if (err)
+                        return err;
+                goto adjust_mean_ec;
+        default:
+                ubi_err("'ubi_io_read_vid_hdr()' returned unknown code %d",
+                        err);
+                return -EINVAL;
         }
 
         vol_id = be32_to_cpu(vidh->vol_id);
@@ -843,7 +999,7 @@ 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;
@@ -858,7 +1014,7 @@ 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;
@@ -870,7 +1026,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
                 }
         }
 
-        if (ec_corr)
+        if (ec_err)
                 ubi_warn("valid VID header but corrupted EC header at PEB %d",
                          pnum);
         err = ubi_scan_add_used(ubi, si, pnum, ec, vidh, bitflips);
@@ -878,7 +1034,7 @@ static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
                 return err;
 
 adjust_mean_ec:
-        if (!ec_corr) {
+        if (!ec_err) {
                 si->ec_sum += ec;
                 si->ec_count += 1;
                 if (ec > si->max_ec)
@@ -904,19 +1060,20 @@ 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");
@@ -931,41 +1088,35 @@ 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;
 }
 
diff --git a/drivers/mtd/ubi/scan.h b/drivers/mtd/ubi/scan.h
index 2576a8d1532b..a3264f0bef2b 100644
--- a/drivers/mtd/ubi/scan.h
+++ b/drivers/mtd/ubi/scan.h
@@ -30,6 +30,7 @@
  * @pnum: physical eraseblock number
  * @lnum: logical eraseblock number
  * @scrub: if this physical eraseblock needs scrubbing
+ * @copy_flag: this LEB is a copy (@copy_flag is set in VID header of this LEB)
  * @sqnum: sequence number
  * @u: unions RB-tree or @list links
  * @u.rb: link in the per-volume RB-tree of &struct ubi_scan_leb objects
@@ -42,7 +43,8 @@ struct ubi_scan_leb {
         int ec;
         int pnum;
         int lnum;
-        int scrub;
+        unsigned int scrub:1;
+        unsigned int copy_flag:1;
         unsigned long long sqnum;
         union {
                 struct rb_node rb;
@@ -91,14 +93,13 @@ struct ubi_scan_volume {
  * @erase: list of physical eraseblocks which have to be erased
  * @alien: list of physical eraseblocks which should not be used by UBI (e.g.,
  *         those belonging to "preserve"-compatible internal volumes)
- * @used_peb_count: count of used PEBs
  * @corr_peb_count: count of PEBs in the @corr list
- * @read_err_count: count of PEBs read with error (%UBI_IO_BAD_HDR_READ was
- *                  returned)
- * @free_peb_count: count of PEBs in the @free list
- * @erase_peb_count: count of PEBs in the @erase list
+ * @empty_peb_count: count of PEBs which are presumably empty (contain only
+ *                   0xFF bytes)
  * @alien_peb_count: count of PEBs in the @alien list
  * @bad_peb_count: count of bad physical eraseblocks
+ * @maybe_bad_peb_count: count of bad physical eraseblocks which are not marked
+ *                       as bad yet, but which look like bad
  * @vols_found: number of volumes found during scanning
  * @highest_vol_id: highest volume ID
  * @is_empty: flag indicating whether the MTD device is empty or not
@@ -119,13 +120,11 @@ struct ubi_scan_info {
         struct list_head free;
         struct list_head erase;
         struct list_head alien;
-        int used_peb_count;
         int corr_peb_count;
-        int read_err_count;
-        int free_peb_count;
-        int erase_peb_count;
+        int empty_peb_count;
         int alien_peb_count;
         int bad_peb_count;
+        int maybe_bad_peb_count;
         int vols_found;
         int highest_vol_id;
         int is_empty;
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 0359e0cce482..0b0149c41fe3 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -85,21 +85,26 @@
 /*
  * Error codes returned by the I/O sub-system.
  *
- * UBI_IO_PEB_EMPTY: the physical eraseblock is empty, i.e. it contains only
- *                   %0xFF bytes
- * UBI_IO_PEB_FREE: the physical eraseblock is free, i.e. it contains only a
- *                  valid erase counter header, and the rest are %0xFF bytes
+ * UBI_IO_FF: the read region of flash contains only 0xFFs
+ * UBI_IO_FF_BITFLIPS: the same as %UBI_IO_FF, but also also there was a data
+ *                     integrity error reported by the MTD driver
+ *                     (uncorrectable ECC error in case of NAND)
  * UBI_IO_BAD_HDR: the EC or VID header is corrupted (bad magic or CRC)
- * UBI_IO_BAD_HDR_READ: the same as %UBI_IO_BAD_HDR, but also there was a read
- *                      error reported by the flash driver
+ * UBI_IO_BAD_HDR_EBADMSG: the same as %UBI_IO_BAD_HDR, but also there was a
+ *                         data integrity error reported by the MTD driver
+ *                         (uncorrectable ECC error in case of NAND)
  * UBI_IO_BITFLIPS: bit-flips were detected and corrected
+ *
+ * Note, it is probably better to have bit-flip and ebadmsg as flags which can
+ * be or'ed with other error code. But this is a big change because there are
+ * may callers, so it does not worth the risk of introducing a bug
  */
 enum {
-        UBI_IO_PEB_EMPTY = 1,
-        UBI_IO_PEB_FREE,
+        UBI_IO_FF = 1,
+        UBI_IO_FF_BITFLIPS,
         UBI_IO_BAD_HDR,
-        UBI_IO_BAD_HDR_READ,
-        UBI_IO_BITFLIPS
+        UBI_IO_BAD_HDR_EBADMSG,
+        UBI_IO_BITFLIPS,
 };
 
 /*
@@ -356,6 +361,8 @@ struct ubi_wl_entry;
  * @peb_size: physical eraseblock size
  * @bad_peb_count: count of bad physical eraseblocks
  * @good_peb_count: count of good physical eraseblocks
+ * @corr_peb_count: count of corrupted physical eraseblocks (preserved and not
+ *                  used by UBI)
  * @erroneous_peb_count: count of erroneous physical eraseblocks in @erroneous
  * @max_erroneous: maximum allowed amount of erroneous physical eraseblocks
  * @min_io_size: minimal input/output unit size of the underlying MTD device
@@ -442,6 +449,7 @@ struct ubi_device {
         int peb_size;
         int bad_peb_count;
         int good_peb_count;
+        int corr_peb_count;
         int erroneous_peb_count;
         int max_erroneous;
         int min_io_size;
@@ -506,6 +514,7 @@ int ubi_calc_data_len(const struct ubi_device *ubi, const void *buf,
                       int length);
 int ubi_check_volume(struct ubi_device *ubi, int vol_id);
 void ubi_calculate_reserved(struct ubi_device *ubi);
+int ubi_check_pattern(const void *buf, uint8_t patt, int size);
 
 /* eba.c */
 int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index e42afab9a9fe..c47620dfc722 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -261,6 +261,9 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
         /* Reserve physical eraseblocks */
         if (vol->reserved_pebs > ubi->avail_pebs) {
                 dbg_err("not enough PEBs, only %d available", ubi->avail_pebs);
+                if (ubi->corr_peb_count)
+                        dbg_err("%d PEBs are corrupted and not used",
+                                ubi->corr_peb_count);
                 err = -ENOSPC;
                 goto out_unlock;
         }
@@ -527,6 +530,9 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
                 if (pebs > ubi->avail_pebs) {
                         dbg_err("not enough PEBs: requested %d, available %d",
                                 pebs, ubi->avail_pebs);
+                        if (ubi->corr_peb_count)
+                                dbg_err("%d PEBs are corrupted and not used",
+                                        ubi->corr_peb_count);
                         spin_unlock(&ubi->volumes_lock);
                         err = -ENOSPC;
                         goto out_free;
diff --git a/drivers/mtd/ubi/vtbl.c b/drivers/mtd/ubi/vtbl.c
index 14c10bed94ee..fcdb7f65fe0b 100644
--- a/drivers/mtd/ubi/vtbl.c
+++ b/drivers/mtd/ubi/vtbl.c
@@ -366,7 +366,7 @@ write_error:
                  * Probably this physical eraseblock went bad, try to pick
                  * another one.
                  */
-                list_add_tail(&new_seb->u.list, &si->corr);
+                list_add(&new_seb->u.list, &si->erase);
                 goto retry;
         }
         kfree(new_seb);
@@ -662,9 +662,13 @@ static int init_volumes(struct ubi_device *ubi, const struct ubi_scan_info *si,
         ubi->vol_count += 1;
         vol->ubi = ubi;
 
-        if (reserved_pebs > ubi->avail_pebs)
+        if (reserved_pebs > ubi->avail_pebs) {
                 ubi_err("not enough PEBs, required %d, available %d",
                         reserved_pebs, ubi->avail_pebs);
+                if (ubi->corr_peb_count)
+                        ubi_err("%d PEBs are corrupted and not used",
+                                ubi->corr_peb_count);
+        }
         ubi->rsvd_pebs += reserved_pebs;
         ubi->avail_pebs -= reserved_pebs;
 
@@ -837,7 +841,7 @@ int ubi_read_volume_table(struct ubi_device *ubi, struct ubi_scan_info *si)
                         return PTR_ERR(ubi->vtbl);
         }
 
-        ubi->avail_pebs = ubi->good_peb_count;
+        ubi->avail_pebs = ubi->good_peb_count - ubi->corr_peb_count;
 
         /*
          * The layout volume is OK, initialize the corresponding in-RAM data
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 97a435672eaf..655bbbe415d9 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -745,7 +745,7 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 
         err = ubi_io_read_vid_hdr(ubi, e1->pnum, vid_hdr, 0);
         if (err && err != UBI_IO_BITFLIPS) {
-                if (err == UBI_IO_PEB_FREE) {
+                if (err == UBI_IO_FF) {
                         /*
                          * We are trying to move PEB without a VID header. UBI
                          * always write VID headers shortly after the PEB was
@@ -759,6 +759,16 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
                         dbg_wl("PEB %d has no VID header", e1->pnum);
                         protect = 1;
                         goto out_not_moved;
+                } else if (err == UBI_IO_FF_BITFLIPS) {
+                        /*
+                         * The same situation as %UBI_IO_FF, but bit-flips were
+                         * detected. It is better to schedule this PEB for
+                         * scrubbing.
+                         */
+                        dbg_wl("PEB %d has no VID header but has bit-flips",
+                               e1->pnum);
+                        scrubbing = 1;
+                        goto out_not_moved;
                 }
 
                 ubi_err("error %d while reading VID header from PEB %d",
@@ -1468,22 +1478,6 @@ int ubi_wl_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
                 ubi->lookuptbl[e->pnum] = e;
         }
 
-        list_for_each_entry(seb, &si->corr, u.list) {
-                cond_resched();
-
-                e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
-                if (!e)
-                        goto out_free;
-
-                e->pnum = seb->pnum;
-                e->ec = seb->ec;
-                ubi->lookuptbl[e->pnum] = e;
-                if (schedule_erase(ubi, e, 0)) {
-                        kmem_cache_free(ubi_wl_entry_slab, e);
-                        goto out_free;
-                }
-        }
-
         ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
                 ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb) {
                         cond_resched();
@@ -1510,6 +1504,9 @@ int ubi_wl_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
         if (ubi->avail_pebs < WL_RESERVED_PEBS) {
                 ubi_err("no enough physical eraseblocks (%d, need %d)",
                         ubi->avail_pebs, WL_RESERVED_PEBS);
+                if (ubi->corr_peb_count)
+                        ubi_err("%d PEBs are corrupted and not used",
+                                ubi->corr_peb_count);
                 goto out_free;
         }
         ubi->avail_pebs -= WL_RESERVED_PEBS;