Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1409 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
new file mode 100644
index 000000000..0e3a76a9e
--- /dev/null
+++ b/drivers/mtd/ubi/io.c
@@ -0,0 +1,1409 @@
+/*
+ * Copyright (c) International Business Machines Corp., 2006
+ * Copyright (c) Nokia Corporation, 2006, 2007
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
+ * the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * Author: Artem Bityutskiy (Битюцкий Артём)
+ */
+
+/*
+ * UBI input/output sub-system.
+ *
+ * This sub-system provides a uniform way to work with all kinds of the
+ * underlying MTD devices. It also implements handy functions for reading and
+ * writing UBI headers.
+ *
+ * We are trying to have a paranoid mindset and not to trust to what we read
+ * from the flash media in order to be more secure and robust. So this
+ * sub-system validates every single header it reads from the flash media.
+ *
+ * Some words about how the eraseblock headers are stored.
+ *
+ * The erase counter header is always stored at offset zero. By default, the
+ * VID header is stored after the EC header at the closest aligned offset
+ * (i.e. aligned to the minimum I/O unit size). Data starts next to the VID
+ * header at the closest aligned offset. But this default layout may be
+ * changed. For example, for different reasons (e.g., optimization) UBI may be
+ * asked to put the VID header at further offset, and even at an unaligned
+ * offset. Of course, if the offset of the VID header is unaligned, UBI adds
+ * proper padding in front of it. Data offset may also be changed but it has to
+ * be aligned.
+ *
+ * About minimal I/O units. In general, UBI assumes flash device model where
+ * there is only one minimal I/O unit size. E.g., in case of NOR flash it is 1,
+ * in case of NAND flash it is a NAND page, etc. This is reported by MTD in the
+ * @ubi->mtd->writesize field. But as an exception, UBI admits use of another
+ * (smaller) minimal I/O unit size for EC and VID headers to make it possible
+ * to do different optimizations.
+ *
+ * This is extremely useful in case of NAND flashes which admit of several
+ * write operations to one NAND page. In this case UBI can fit EC and VID
+ * headers at one NAND page. Thus, UBI may use "sub-page" size as the minimal
+ * I/O unit for the headers (the @ubi->hdrs_min_io_size field). But it still
+ * reports NAND page size (@ubi->min_io_size) as a minimal I/O unit for the UBI
+ * users.
+ *
+ * Example: some Samsung NANDs with 2KiB pages allow 4x 512-byte writes, so
+ * although the minimal I/O unit is 2K, UBI uses 512 bytes for EC and VID
+ * headers.
+ *
+ * Q: why not just to treat sub-page as a minimal I/O unit of this flash
+ * device, e.g., make @ubi->min_io_size = 512 in the example above?
+ *
+ * A: because when writing a sub-page, MTD still writes a full 2K page but the
+ * bytes which are not relevant to the sub-page are 0xFF. So, basically,
+ * writing 4x512 sub-pages is 4 times slower than writing one 2KiB NAND page.
+ * Thus, we prefer to use sub-pages only for EC and VID headers.
+ *
+ * As it was noted above, the VID header may start at a non-aligned offset.
+ * For example, in case of a 2KiB page NAND flash with a 512 bytes sub-page,
+ * the VID header may reside at offset 1984 which is the last 64 bytes of the
+ * last sub-page (EC header is always at offset zero). This causes some
+ * difficulties when reading and writing VID headers.
+ *
+ * Suppose we have a 64-byte buffer and we read a VID header at it. We change
+ * the data and want to write this VID header out. As we can only write in
+ * 512-byte chunks, we have to allocate one more buffer and copy our VID header
+ * to offset 448 of this buffer.
+ *
+ * The I/O sub-system does the following trick in order to avoid this extra
+ * copy. It always allocates a @ubi->vid_hdr_alsize bytes buffer for the VID
+ * header and returns a pointer to offset @ubi->vid_hdr_shift of this buffer.
+ * When the VID header is being written out, it shifts the VID header pointer
+ * back and writes the whole sub-page.
+ */
+
+#include <linux/crc32.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include "ubi.h"
+
+static int self_check_not_bad(const struct ubi_device *ubi, int pnum);
+static int self_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum);
+static int self_check_ec_hdr(const struct ubi_device *ubi, int pnum,
+			     const struct ubi_ec_hdr *ec_hdr);
+static int self_check_peb_vid_hdr(const struct ubi_device *ubi, int pnum);
+static int self_check_vid_hdr(const struct ubi_device *ubi, int pnum,
+			      const struct ubi_vid_hdr *vid_hdr);
+static int self_check_write(struct ubi_device *ubi, const void *buf, int pnum,
+			    int offset, int len);
+
+/**
+ * ubi_io_read - read data from a physical eraseblock.
+ * @ubi: UBI device description object
+ * @buf: buffer where to store the read data
+ * @pnum: physical eraseblock number to read from
+ * @offset: offset within the physical eraseblock from where to read
+ * @len: how many bytes to read
+ *
+ * This function reads data from offset @offset of physical eraseblock @pnum
+ * and stores the read data in the @buf buffer. The following return codes are
+ * possible:
+ *
+ * o %0 if all the requested data were successfully read;
+ * o %UBI_IO_BITFLIPS if all the requested data were successfully read, but
+ *   correctable bit-flips were detected; this is harmless but may indicate
+ *   that this eraseblock may become bad soon (but do not have to);
+ * o %-EBADMSG if the MTD subsystem reported about data integrity problems, for
+ *   example it can be an ECC error in case of NAND; this most probably means
+ *   that the data is corrupted;
+ * o %-EIO if some I/O error occurred;
+ * o other negative error codes in case of other errors.
+ */
+int ubi_io_read(const struct ubi_device *ubi, void *buf, int pnum, int offset,
+		int len)
+{
+	int err, retries = 0;
+	size_t read;
+	loff_t addr;
+
+	dbg_io("read %d bytes from PEB %d:%d", len, pnum, offset);
+
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+	ubi_assert(offset >= 0 && offset + len <= ubi->peb_size);
+	ubi_assert(len > 0);
+
+	err = self_check_not_bad(ubi, pnum);
+	if (err)
+		return err;
+
+	/*
+	 * Deliberately corrupt the buffer to improve robustness. Indeed, if we
+	 * do not do this, the following may happen:
+	 * 1. The buffer contains data from previous operation, e.g., read from
+	 *    another PEB previously. The data looks like expected, e.g., if we
+	 *    just do not read anything and return - the caller would not
+	 *    notice this. E.g., if we are reading a VID header, the buffer may
+	 *    contain a valid VID header from another PEB.
+	 * 2. The driver is buggy and returns us success or -EBADMSG or
+	 *    -EUCLEAN, but it does not actually put any data to the buffer.
+	 *
+	 * This may confuse UBI or upper layers - they may think the buffer
+	 * contains valid data while in fact it is just old data. This is
+	 * especially possible because UBI (and UBIFS) relies on CRC, and
+	 * treats data as correct even in case of ECC errors if the CRC is
+	 * correct.
+	 *
+	 * Try to prevent this situation by changing the first byte of the
+	 * buffer.
+	 */
+	*((uint8_t *)buf) ^= 0xFF;
+
+	addr = (loff_t)pnum * ubi->peb_size + offset;
+retry:
+	err = mtd_read(ubi->mtd, addr, len, &read, buf);
+	if (err) {
+		const char *errstr = mtd_is_eccerr(err) ? " (ECC error)" : "";
+
+		if (mtd_is_bitflip(err)) {
+			/*
+			 * -EUCLEAN is reported if there was a bit-flip which
+			 * was corrected, so this is harmless.
+			 *
+			 * We do not report about it here unless debugging is
+			 * enabled. A corresponding message will be printed
+			 * later, when it is has been scrubbed.
+			 */
+			ubi_msg(ubi, "fixable bit-flip detected at PEB %d",
+				pnum);
+			ubi_assert(len == read);
+			return UBI_IO_BITFLIPS;
+		}
+
+		if (retries++ < UBI_IO_RETRIES) {
+			ubi_warn(ubi, "error %d%s while reading %d bytes from PEB %d:%d, read only %zd bytes, retry",
+				 err, errstr, len, pnum, offset, read);
+			yield();
+			goto retry;
+		}
+
+		ubi_err(ubi, "error %d%s while reading %d bytes from PEB %d:%d, read %zd bytes",
+			err, errstr, len, pnum, offset, read);
+		dump_stack();
+
+		/*
+		 * The driver should never return -EBADMSG if it failed to read
+		 * all the requested data. But some buggy drivers might do
+		 * this, so we change it to -EIO.
+		 */
+		if (read != len && mtd_is_eccerr(err)) {
+			ubi_assert(0);
+			err = -EIO;
+		}
+	} else {
+		ubi_assert(len == read);
+
+		if (ubi_dbg_is_bitflip(ubi)) {
+			dbg_gen("bit-flip (emulated)");
+			err = UBI_IO_BITFLIPS;
+		}
+	}
+
+	return err;
+}
+
+/**
+ * ubi_io_write - write data to a physical eraseblock.
+ * @ubi: UBI device description object
+ * @buf: buffer with the data to write
+ * @pnum: physical eraseblock number to write to
+ * @offset: offset within the physical eraseblock where to write
+ * @len: how many bytes to write
+ *
+ * This function writes @len bytes of data from buffer @buf to offset @offset
+ * of physical eraseblock @pnum. If all the data were successfully written,
+ * zero is returned. If an error occurred, this function returns a negative
+ * error code. If %-EIO is returned, the physical eraseblock most probably went
+ * bad.
+ *
+ * Note, in case of an error, it is possible that something was still written
+ * to the flash media, but may be some garbage.
+ */
+int ubi_io_write(struct ubi_device *ubi, const void *buf, int pnum, int offset,
+		 int len)
+{
+	int err;
+	size_t written;
+	loff_t addr;
+
+	dbg_io("write %d bytes to PEB %d:%d", len, pnum, offset);
+
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+	ubi_assert(offset >= 0 && offset + len <= ubi->peb_size);
+	ubi_assert(offset % ubi->hdrs_min_io_size == 0);
+	ubi_assert(len > 0 && len % ubi->hdrs_min_io_size == 0);
+
+	if (ubi->ro_mode) {
+		ubi_err(ubi, "read-only mode");
+		return -EROFS;
+	}
+
+	err = self_check_not_bad(ubi, pnum);
+	if (err)
+		return err;
+
+	/* The area we are writing to has to contain all 0xFF bytes */
+	err = ubi_self_check_all_ff(ubi, pnum, offset, len);
+	if (err)
+		return err;
+
+	if (offset >= ubi->leb_start) {
+		/*
+		 * We write to the data area of the physical eraseblock. Make
+		 * sure it has valid EC and VID headers.
+		 */
+		err = self_check_peb_ec_hdr(ubi, pnum);
+		if (err)
+			return err;
+		err = self_check_peb_vid_hdr(ubi, pnum);
+		if (err)
+			return err;
+	}
+
+	if (ubi_dbg_is_write_failure(ubi)) {
+		ubi_err(ubi, "cannot write %d bytes to PEB %d:%d (emulated)",
+			len, pnum, offset);
+		dump_stack();
+		return -EIO;
+	}
+
+	addr = (loff_t)pnum * ubi->peb_size + offset;
+	err = mtd_write(ubi->mtd, addr, len, &written, buf);
+	if (err) {
+		ubi_err(ubi, "error %d while writing %d bytes to PEB %d:%d, written %zd bytes",
+			err, len, pnum, offset, written);
+		dump_stack();
+		ubi_dump_flash(ubi, pnum, offset, len);
+	} else
+		ubi_assert(written == len);
+
+	if (!err) {
+		err = self_check_write(ubi, buf, pnum, offset, len);
+		if (err)
+			return err;
+
+		/*
+		 * Since we always write sequentially, the rest of the PEB has
+		 * to contain only 0xFF bytes.
+		 */
+		offset += len;
+		len = ubi->peb_size - offset;
+		if (len)
+			err = ubi_self_check_all_ff(ubi, pnum, offset, len);
+	}
+
+	return err;
+}
+
+/**
+ * do_sync_erase - synchronously erase a physical eraseblock.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to erase
+ *
+ * This function synchronously erases physical eraseblock @pnum and returns
+ * zero in case of success and a negative error code in case of failure. If
+ * %-EIO is returned, the physical eraseblock most probably went bad.
+ */
+static int do_sync_erase(struct ubi_device *ubi, int pnum)
+{
+	int err, retries = 0;
+	struct erase_info ei;
+
+	dbg_io("erase PEB %d", pnum);
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+
+	if (ubi->ro_mode) {
+		ubi_err(ubi, "read-only mode");
+		return -EROFS;
+	}
+
+retry:
+	memset(&ei, 0, sizeof(struct erase_info));
+
+	ei.addr     = (loff_t)pnum * ubi->peb_size;
+	ei.len      = ubi->peb_size;
+
+	err = mtd_erase(ubi->mtd, &ei);
+	if (err) {
+		if (retries++ < UBI_IO_RETRIES) {
+			ubi_warn(ubi, "error %d while erasing PEB %d, retry",
+				 err, pnum);
+			yield();
+			goto retry;
+		}
+		ubi_err(ubi, "cannot erase PEB %d, error %d", pnum, err);
+		dump_stack();
+		return err;
+	}
+
+	err = ubi_self_check_all_ff(ubi, pnum, 0, ubi->peb_size);
+	if (err)
+		return err;
+
+	if (ubi_dbg_is_erase_failure(ubi)) {
+		ubi_err(ubi, "cannot erase PEB %d (emulated)", pnum);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/* Patterns to write to a physical eraseblock when torturing it */
+static uint8_t patterns[] = {0xa5, 0x5a, 0x0};
+
+/**
+ * torture_peb - test a supposedly bad physical eraseblock.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to test
+ *
+ * This function returns %-EIO if the physical eraseblock did not pass the
+ * test, a positive number of erase operations done if the test was
+ * successfully passed, and other negative error codes in case of other errors.
+ */
+static int torture_peb(struct ubi_device *ubi, int pnum)
+{
+	int err, i, patt_count;
+
+	ubi_msg(ubi, "run torture test for PEB %d", pnum);
+	patt_count = ARRAY_SIZE(patterns);
+	ubi_assert(patt_count > 0);
+
+	mutex_lock(&ubi->buf_mutex);
+	for (i = 0; i < patt_count; i++) {
+		err = do_sync_erase(ubi, pnum);
+		if (err)
+			goto out;
+
+		/* Make sure the PEB contains only 0xFF bytes */
+		err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
+		if (err)
+			goto out;
+
+		err = ubi_check_pattern(ubi->peb_buf, 0xFF, ubi->peb_size);
+		if (err == 0) {
+			ubi_err(ubi, "erased PEB %d, but a non-0xFF byte found",
+				pnum);
+			err = -EIO;
+			goto out;
+		}
+
+		/* Write a pattern and check it */
+		memset(ubi->peb_buf, patterns[i], ubi->peb_size);
+		err = ubi_io_write(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
+		if (err)
+			goto out;
+
+		memset(ubi->peb_buf, ~patterns[i], ubi->peb_size);
+		err = ubi_io_read(ubi, ubi->peb_buf, pnum, 0, ubi->peb_size);
+		if (err)
+			goto out;
+
+		err = ubi_check_pattern(ubi->peb_buf, patterns[i],
+					ubi->peb_size);
+		if (err == 0) {
+			ubi_err(ubi, "pattern %x checking failed for PEB %d",
+				patterns[i], pnum);
+			err = -EIO;
+			goto out;
+		}
+	}
+
+	err = patt_count;
+	ubi_msg(ubi, "PEB %d passed torture test, do not mark it as bad", pnum);
+
+out:
+	mutex_unlock(&ubi->buf_mutex);
+	if (err == UBI_IO_BITFLIPS || mtd_is_eccerr(err)) {
+		/*
+		 * If a bit-flip or data integrity error was detected, the test
+		 * has not passed because it happened on a freshly erased
+		 * physical eraseblock which means something is wrong with it.
+		 */
+		ubi_err(ubi, "read problems on freshly erased PEB %d, must be bad",
+			pnum);
+		err = -EIO;
+	}
+	return err;
+}
+
+/**
+ * nor_erase_prepare - prepare a NOR flash PEB for erasure.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number to prepare
+ *
+ * NOR flash, or at least some of them, have peculiar embedded PEB erasure
+ * algorithm: the PEB is first filled with zeroes, then it is erased. And
+ * filling with zeroes starts from the end of the PEB. This was observed with
+ * Spansion S29GL512N NOR flash.
+ *
+ * This means that in case of a power cut we may end up with intact data at the
+ * beginning of the PEB, and all zeroes at the end of PEB. In other words, the
+ * EC and VID headers are OK, but a large chunk of data at the end of PEB is
+ * zeroed. This makes UBI mistakenly treat this PEB as used and associate it
+ * with an LEB, which leads to subsequent failures (e.g., UBIFS fails).
+ *
+ * This function is called before erasing NOR PEBs and it zeroes out EC and VID
+ * magic numbers in order to invalidate them and prevent the failures. Returns
+ * zero in case of success and a negative error code in case of failure.
+ */
+static int nor_erase_prepare(struct ubi_device *ubi, int pnum)
+{
+	int err;
+	size_t written;
+	loff_t addr;
+	uint32_t data = 0;
+	struct ubi_ec_hdr ec_hdr;
+	struct ubi_vid_io_buf vidb;
+
+	/*
+	 * Note, we cannot generally define VID header buffers on stack,
+	 * because of the way we deal with these buffers (see the header
+	 * comment in this file). But we know this is a NOR-specific piece of
+	 * code, so we can do this. But yes, this is error-prone and we should
+	 * (pre-)allocate VID header buffer instead.
+	 */
+	struct ubi_vid_hdr vid_hdr;
+
+	/*
+	 * If VID or EC is valid, we have to corrupt them before erasing.
+	 * It is important to first invalidate the EC header, and then the VID
+	 * header. Otherwise a power cut may lead to valid EC header and
+	 * invalid VID header, in which case UBI will treat this PEB as
+	 * corrupted and will try to preserve it, and print scary warnings.
+	 */
+	addr = (loff_t)pnum * ubi->peb_size;
+	err = ubi_io_read_ec_hdr(ubi, pnum, &ec_hdr, 0);
+	if (err != UBI_IO_BAD_HDR_EBADMSG && err != UBI_IO_BAD_HDR &&
+	    err != UBI_IO_FF){
+		err = mtd_write(ubi->mtd, addr, 4, &written, (void *)&data);
+		if(err)
+			goto error;
+	}
+
+	ubi_init_vid_buf(ubi, &vidb, &vid_hdr);
+	ubi_assert(&vid_hdr == ubi_get_vid_hdr(&vidb));
+
+	err = ubi_io_read_vid_hdr(ubi, pnum, &vidb, 0);
+	if (err != UBI_IO_BAD_HDR_EBADMSG && err != UBI_IO_BAD_HDR &&
+	    err != UBI_IO_FF){
+		addr += ubi->vid_hdr_aloffset;
+		err = mtd_write(ubi->mtd, addr, 4, &written, (void *)&data);
+		if (err)
+			goto error;
+	}
+	return 0;
+
+error:
+	/*
+	 * The PEB contains a valid VID or EC header, but we cannot invalidate
+	 * it. Supposedly the flash media or the driver is screwed up, so
+	 * return an error.
+	 */
+	ubi_err(ubi, "cannot invalidate PEB %d, write returned %d", pnum, err);
+	ubi_dump_flash(ubi, pnum, 0, ubi->peb_size);
+	return -EIO;
+}
+
+/**
+ * ubi_io_sync_erase - synchronously erase a physical eraseblock.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number to erase
+ * @torture: if this physical eraseblock has to be tortured
+ *
+ * This function synchronously erases physical eraseblock @pnum. If @torture
+ * flag is not zero, the physical eraseblock is checked by means of writing
+ * different patterns to it and reading them back. If the torturing is enabled,
+ * the physical eraseblock is erased more than once.
+ *
+ * This function returns the number of erasures made in case of success, %-EIO
+ * if the erasure failed or the torturing test failed, and other negative error
+ * codes in case of other errors. Note, %-EIO means that the physical
+ * eraseblock is bad.
+ */
+int ubi_io_sync_erase(struct ubi_device *ubi, int pnum, int torture)
+{
+	int err, ret = 0;
+
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+
+	err = self_check_not_bad(ubi, pnum);
+	if (err != 0)
+		return err;
+
+	if (ubi->ro_mode) {
+		ubi_err(ubi, "read-only mode");
+		return -EROFS;
+	}
+
+	if (ubi->nor_flash) {
+		err = nor_erase_prepare(ubi, pnum);
+		if (err)
+			return err;
+	}
+
+	if (torture) {
+		ret = torture_peb(ubi, pnum);
+		if (ret < 0)
+			return ret;
+	}
+
+	err = do_sync_erase(ubi, pnum);
+	if (err)
+		return err;
+
+	return ret + 1;
+}
+
+/**
+ * ubi_io_is_bad - check if a physical eraseblock is bad.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ *
+ * This function returns a positive number if the physical eraseblock is bad,
+ * zero if not, and a negative error code if an error occurred.
+ */
+int ubi_io_is_bad(const struct ubi_device *ubi, int pnum)
+{
+	struct mtd_info *mtd = ubi->mtd;
+
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+
+	if (ubi->bad_allowed) {
+		int ret;
+
+		ret = mtd_block_isbad(mtd, (loff_t)pnum * ubi->peb_size);
+		if (ret < 0)
+			ubi_err(ubi, "error %d while checking if PEB %d is bad",
+				ret, pnum);
+		else if (ret)
+			dbg_io("PEB %d is bad", pnum);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * ubi_io_mark_bad - mark a physical eraseblock as bad.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to mark
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ */
+int ubi_io_mark_bad(const struct ubi_device *ubi, int pnum)
+{
+	int err;
+	struct mtd_info *mtd = ubi->mtd;
+
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+
+	if (ubi->ro_mode) {
+		ubi_err(ubi, "read-only mode");
+		return -EROFS;
+	}
+
+	if (!ubi->bad_allowed)
+		return 0;
+
+	err = mtd_block_markbad(mtd, (loff_t)pnum * ubi->peb_size);
+	if (err)
+		ubi_err(ubi, "cannot mark PEB %d bad, error %d", pnum, err);
+	return err;
+}
+
+/**
+ * validate_ec_hdr - validate an erase counter header.
+ * @ubi: UBI device description object
+ * @ec_hdr: the erase counter header to check
+ *
+ * This function returns zero if the erase counter header is OK, and %1 if
+ * not.
+ */
+static int validate_ec_hdr(const struct ubi_device *ubi,
+			   const struct ubi_ec_hdr *ec_hdr)
+{
+	long long ec;
+	int vid_hdr_offset, leb_start;
+
+	ec = be64_to_cpu(ec_hdr->ec);
+	vid_hdr_offset = be32_to_cpu(ec_hdr->vid_hdr_offset);
+	leb_start = be32_to_cpu(ec_hdr->data_offset);
+
+	if (ec_hdr->version != UBI_VERSION) {
+		ubi_err(ubi, "node with incompatible UBI version found: this UBI version is %d, image version is %d",
+			UBI_VERSION, (int)ec_hdr->version);
+		goto bad;
+	}
+
+	if (vid_hdr_offset != ubi->vid_hdr_offset) {
+		ubi_err(ubi, "bad VID header offset %d, expected %d",
+			vid_hdr_offset, ubi->vid_hdr_offset);
+		goto bad;
+	}
+
+	if (leb_start != ubi->leb_start) {
+		ubi_err(ubi, "bad data offset %d, expected %d",
+			leb_start, ubi->leb_start);
+		goto bad;
+	}
+
+	if (ec < 0 || ec > UBI_MAX_ERASECOUNTER) {
+		ubi_err(ubi, "bad erase counter %lld", ec);
+		goto bad;
+	}
+
+	return 0;
+
+bad:
+	ubi_err(ubi, "bad EC header");
+	ubi_dump_ec_hdr(ec_hdr);
+	dump_stack();
+	return 1;
+}
+
+/**
+ * ubi_io_read_ec_hdr - read and check an erase counter header.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock to read from
+ * @ec_hdr: a &struct ubi_ec_hdr object where to store the read erase counter
+ * header
+ * @verbose: be verbose if the header is corrupted or was not found
+ *
+ * This function reads erase counter header from physical eraseblock @pnum and
+ * stores it in @ec_hdr. This function also checks CRC checksum of the read
+ * erase counter header. The following codes may be returned:
+ *
+ * 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 (but may be not);
+ * o %UBI_IO_BAD_HDR if the erase counter header is corrupted (a CRC error);
+ * 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;
+	uint32_t crc, magic, hdr_crc;
+
+	dbg_io("read EC header from PEB %d", pnum);
+	ubi_assert(pnum >= 0 && pnum < ubi->peb_count);
+
+	read_err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
+	if (read_err) {
+		if (read_err != UBI_IO_BITFLIPS && !mtd_is_eccerr(read_err))
+			return read_err;
+
+		/*
+		 * We read all the data, but either a correctable 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.
+		 */
+	}
+
+	magic = be32_to_cpu(ec_hdr->magic);
+	if (magic != UBI_EC_HDR_MAGIC) {
+		if (mtd_is_eccerr(read_err))
+			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 (ubi_check_pattern(ec_hdr, 0xFF, UBI_EC_HDR_SIZE)) {
+			/* The physical eraseblock is supposedly empty */
+			if (verbose)
+				ubi_warn(ubi, "no EC header found at PEB %d, only 0xFF bytes",
+					 pnum);
+			dbg_bld("no EC header found at PEB %d, only 0xFF bytes",
+				pnum);
+			if (!read_err)
+				return UBI_IO_FF;
+			else
+				return UBI_IO_FF_BITFLIPS;
+		}
+
+		/*
+		 * This is not a valid erase counter header, and these are not
+		 * 0xFF bytes. Report that the header is corrupted.
+		 */
+		if (verbose) {
+			ubi_warn(ubi, "bad magic number at PEB %d: %08x instead of %08x",
+				 pnum, magic, UBI_EC_HDR_MAGIC);
+			ubi_dump_ec_hdr(ec_hdr);
+		}
+		dbg_bld("bad magic number at PEB %d: %08x instead of %08x",
+			pnum, magic, UBI_EC_HDR_MAGIC);
+		return UBI_IO_BAD_HDR;
+	}
+
+	crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
+	hdr_crc = be32_to_cpu(ec_hdr->hdr_crc);
+
+	if (hdr_crc != crc) {
+		if (verbose) {
+			ubi_warn(ubi, "bad EC header CRC at PEB %d, calculated %#08x, read %#08x",
+				 pnum, crc, hdr_crc);
+			ubi_dump_ec_hdr(ec_hdr);
+		}
+		dbg_bld("bad EC header CRC at PEB %d, calculated %#08x, read %#08x",
+			pnum, crc, hdr_crc);
+
+		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 */
+	err = validate_ec_hdr(ubi, ec_hdr);
+	if (err) {
+		ubi_err(ubi, "validation failed for PEB %d", pnum);
+		return -EINVAL;
+	}
+
+	/*
+	 * If there was %-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;
+}
+
+/**
+ * ubi_io_write_ec_hdr - write an erase counter header.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock to write to
+ * @ec_hdr: the erase counter header to write
+ *
+ * This function writes erase counter header described by @ec_hdr to physical
+ * eraseblock @pnum. It also fills most fields of @ec_hdr before writing, so
+ * the caller do not have to fill them. Callers must only fill the @ec_hdr->ec
+ * field.
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure. If %-EIO is returned, the physical eraseblock most probably
+ * went bad.
+ */
+int ubi_io_write_ec_hdr(struct ubi_device *ubi, int pnum,
+			struct ubi_ec_hdr *ec_hdr)
+{
+	int err;
+	uint32_t crc;
+
+	dbg_io("write EC header to PEB %d", pnum);
+	ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);
+
+	ec_hdr->magic = cpu_to_be32(UBI_EC_HDR_MAGIC);
+	ec_hdr->version = UBI_VERSION;
+	ec_hdr->vid_hdr_offset = cpu_to_be32(ubi->vid_hdr_offset);
+	ec_hdr->data_offset = cpu_to_be32(ubi->leb_start);
+	ec_hdr->image_seq = cpu_to_be32(ubi->image_seq);
+	crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
+	ec_hdr->hdr_crc = cpu_to_be32(crc);
+
+	err = self_check_ec_hdr(ubi, pnum, ec_hdr);
+	if (err)
+		return err;
+
+	if (ubi_dbg_power_cut(ubi, POWER_CUT_EC_WRITE))
+		return -EROFS;
+
+	err = ubi_io_write(ubi, ec_hdr, pnum, 0, ubi->ec_hdr_alsize);
+	return err;
+}
+
+/**
+ * validate_vid_hdr - validate a volume identifier header.
+ * @ubi: UBI device description object
+ * @vid_hdr: the volume identifier header to check
+ *
+ * This function checks that data stored in the volume identifier header
+ * @vid_hdr. Returns zero if the VID header is OK and %1 if not.
+ */
+static int validate_vid_hdr(const struct ubi_device *ubi,
+			    const struct ubi_vid_hdr *vid_hdr)
+{
+	int vol_type = vid_hdr->vol_type;
+	int copy_flag = vid_hdr->copy_flag;
+	int vol_id = be32_to_cpu(vid_hdr->vol_id);
+	int lnum = be32_to_cpu(vid_hdr->lnum);
+	int compat = vid_hdr->compat;
+	int data_size = be32_to_cpu(vid_hdr->data_size);
+	int used_ebs = be32_to_cpu(vid_hdr->used_ebs);
+	int data_pad = be32_to_cpu(vid_hdr->data_pad);
+	int data_crc = be32_to_cpu(vid_hdr->data_crc);
+	int usable_leb_size = ubi->leb_size - data_pad;
+
+	if (copy_flag != 0 && copy_flag != 1) {
+		ubi_err(ubi, "bad copy_flag");
+		goto bad;
+	}
+
+	if (vol_id < 0 || lnum < 0 || data_size < 0 || used_ebs < 0 ||
+	    data_pad < 0) {
+		ubi_err(ubi, "negative values");
+		goto bad;
+	}
+
+	if (vol_id >= UBI_MAX_VOLUMES && vol_id < UBI_INTERNAL_VOL_START) {
+		ubi_err(ubi, "bad vol_id");
+		goto bad;
+	}
+
+	if (vol_id < UBI_INTERNAL_VOL_START && compat != 0) {
+		ubi_err(ubi, "bad compat");
+		goto bad;
+	}
+
+	if (vol_id >= UBI_INTERNAL_VOL_START && compat != UBI_COMPAT_DELETE &&
+	    compat != UBI_COMPAT_RO && compat != UBI_COMPAT_PRESERVE &&
+	    compat != UBI_COMPAT_REJECT) {
+		ubi_err(ubi, "bad compat");
+		goto bad;
+	}
+
+	if (vol_type != UBI_VID_DYNAMIC && vol_type != UBI_VID_STATIC) {
+		ubi_err(ubi, "bad vol_type");
+		goto bad;
+	}
+
+	if (data_pad >= ubi->leb_size / 2) {
+		ubi_err(ubi, "bad data_pad");
+		goto bad;
+	}
+
+	if (data_size > ubi->leb_size) {
+		ubi_err(ubi, "bad data_size");
+		goto bad;
+	}
+
+	if (vol_type == UBI_VID_STATIC) {
+		/*
+		 * Although from high-level point of view static volumes may
+		 * contain zero bytes of data, but no VID headers can contain
+		 * zero at these fields, because they empty volumes do not have
+		 * mapped logical eraseblocks.
+		 */
+		if (used_ebs == 0) {
+			ubi_err(ubi, "zero used_ebs");
+			goto bad;
+		}
+		if (data_size == 0) {
+			ubi_err(ubi, "zero data_size");
+			goto bad;
+		}
+		if (lnum < used_ebs - 1) {
+			if (data_size != usable_leb_size) {
+				ubi_err(ubi, "bad data_size");
+				goto bad;
+			}
+		} else if (lnum == used_ebs - 1) {
+			if (data_size == 0) {
+				ubi_err(ubi, "bad data_size at last LEB");
+				goto bad;
+			}
+		} else {
+			ubi_err(ubi, "too high lnum");
+			goto bad;
+		}
+	} else {
+		if (copy_flag == 0) {
+			if (data_crc != 0) {
+				ubi_err(ubi, "non-zero data CRC");
+				goto bad;
+			}
+			if (data_size != 0) {
+				ubi_err(ubi, "non-zero data_size");
+				goto bad;
+			}
+		} else {
+			if (data_size == 0) {
+				ubi_err(ubi, "zero data_size of copy");
+				goto bad;
+			}
+		}
+		if (used_ebs != 0) {
+			ubi_err(ubi, "bad used_ebs");
+			goto bad;
+		}
+	}
+
+	return 0;
+
+bad:
+	ubi_err(ubi, "bad VID header");
+	ubi_dump_vid_hdr(vid_hdr);
+	dump_stack();
+	return 1;
+}
+
+/**
+ * ubi_io_read_vid_hdr - read and check a volume identifier header.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number to read from
+ * @vidb: the volume identifier buffer to store data in
+ * @verbose: be verbose if the header is corrupted or wasn't found
+ *
+ * This function reads the volume identifier header from physical eraseblock
+ * @pnum and stores it in @vidb. It also checks CRC checksum of the read
+ * volume identifier header. The error codes are the same as in
+ * 'ubi_io_read_ec_hdr()'.
+ *
+ * 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_io_buf *vidb, int verbose)
+{
+	int err, read_err;
+	uint32_t crc, magic, hdr_crc;
+	struct ubi_vid_hdr *vid_hdr = ubi_get_vid_hdr(vidb);
+	void *p = vidb->buffer;
+
+	dbg_io("read VID header from PEB %d", pnum);
+	ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);
+
+	read_err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
+			  ubi->vid_hdr_shift + UBI_VID_HDR_SIZE);
+	if (read_err && read_err != UBI_IO_BITFLIPS && !mtd_is_eccerr(read_err))
+		return read_err;
+
+	magic = be32_to_cpu(vid_hdr->magic);
+	if (magic != UBI_VID_HDR_MAGIC) {
+		if (mtd_is_eccerr(read_err))
+			return UBI_IO_BAD_HDR_EBADMSG;
+
+		if (ubi_check_pattern(vid_hdr, 0xFF, UBI_VID_HDR_SIZE)) {
+			if (verbose)
+				ubi_warn(ubi, "no VID header found at PEB %d, only 0xFF bytes",
+					 pnum);
+			dbg_bld("no VID header found at PEB %d, only 0xFF bytes",
+				pnum);
+			if (!read_err)
+				return UBI_IO_FF;
+			else
+				return UBI_IO_FF_BITFLIPS;
+		}
+
+		if (verbose) {
+			ubi_warn(ubi, "bad magic number at PEB %d: %08x instead of %08x",
+				 pnum, magic, UBI_VID_HDR_MAGIC);
+			ubi_dump_vid_hdr(vid_hdr);
+		}
+		dbg_bld("bad magic number at PEB %d: %08x instead of %08x",
+			pnum, magic, UBI_VID_HDR_MAGIC);
+		return UBI_IO_BAD_HDR;
+	}
+
+	crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_VID_HDR_SIZE_CRC);
+	hdr_crc = be32_to_cpu(vid_hdr->hdr_crc);
+
+	if (hdr_crc != crc) {
+		if (verbose) {
+			ubi_warn(ubi, "bad CRC at PEB %d, calculated %#08x, read %#08x",
+				 pnum, crc, hdr_crc);
+			ubi_dump_vid_hdr(vid_hdr);
+		}
+		dbg_bld("bad CRC at PEB %d, calculated %#08x, read %#08x",
+			pnum, crc, hdr_crc);
+		if (!read_err)
+			return UBI_IO_BAD_HDR;
+		else
+			return UBI_IO_BAD_HDR_EBADMSG;
+	}
+
+	err = validate_vid_hdr(ubi, vid_hdr);
+	if (err) {
+		ubi_err(ubi, "validation failed for PEB %d", pnum);
+		return -EINVAL;
+	}
+
+	return read_err ? UBI_IO_BITFLIPS : 0;
+}
+
+/**
+ * ubi_io_write_vid_hdr - write a volume identifier header.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to write to
+ * @vidb: the volume identifier buffer to write
+ *
+ * This function writes the volume identifier header described by @vid_hdr to
+ * physical eraseblock @pnum. This function automatically fills the
+ * @vidb->hdr->magic and the @vidb->hdr->version fields, as well as calculates
+ * header CRC checksum and stores it at vidb->hdr->hdr_crc.
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure. If %-EIO is returned, the physical eraseblock probably went
+ * bad.
+ */
+int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
+			 struct ubi_vid_io_buf *vidb)
+{
+	struct ubi_vid_hdr *vid_hdr = ubi_get_vid_hdr(vidb);
+	int err;
+	uint32_t crc;
+	void *p = vidb->buffer;
+
+	dbg_io("write VID header to PEB %d", pnum);
+	ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);
+
+	err = self_check_peb_ec_hdr(ubi, pnum);
+	if (err)
+		return err;
+
+	vid_hdr->magic = cpu_to_be32(UBI_VID_HDR_MAGIC);
+	vid_hdr->version = UBI_VERSION;
+	crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_VID_HDR_SIZE_CRC);
+	vid_hdr->hdr_crc = cpu_to_be32(crc);
+
+	err = self_check_vid_hdr(ubi, pnum, vid_hdr);
+	if (err)
+		return err;
+
+	if (ubi_dbg_power_cut(ubi, POWER_CUT_VID_WRITE))
+		return -EROFS;
+
+	err = ubi_io_write(ubi, p, pnum, ubi->vid_hdr_aloffset,
+			   ubi->vid_hdr_alsize);
+	return err;
+}
+
+/**
+ * self_check_not_bad - ensure that a physical eraseblock is not bad.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number to check
+ *
+ * This function returns zero if the physical eraseblock is good, %-EINVAL if
+ * it is bad and a negative error code if an error occurred.
+ */
+static int self_check_not_bad(const struct ubi_device *ubi, int pnum)
+{
+	int err;
+
+	if (!ubi_dbg_chk_io(ubi))
+		return 0;
+
+	err = ubi_io_is_bad(ubi, pnum);
+	if (!err)
+		return err;
+
+	ubi_err(ubi, "self-check failed for PEB %d", pnum);
+	dump_stack();
+	return err > 0 ? -EINVAL : err;
+}
+
+/**
+ * self_check_ec_hdr - check if an erase counter header is all right.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number the erase counter header belongs to
+ * @ec_hdr: the erase counter header to check
+ *
+ * This function returns zero if the erase counter header contains valid
+ * values, and %-EINVAL if not.
+ */
+static int self_check_ec_hdr(const struct ubi_device *ubi, int pnum,
+			     const struct ubi_ec_hdr *ec_hdr)
+{
+	int err;
+	uint32_t magic;
+
+	if (!ubi_dbg_chk_io(ubi))
+		return 0;
+
+	magic = be32_to_cpu(ec_hdr->magic);
+	if (magic != UBI_EC_HDR_MAGIC) {
+		ubi_err(ubi, "bad magic %#08x, must be %#08x",
+			magic, UBI_EC_HDR_MAGIC);
+		goto fail;
+	}
+
+	err = validate_ec_hdr(ubi, ec_hdr);
+	if (err) {
+		ubi_err(ubi, "self-check failed for PEB %d", pnum);
+		goto fail;
+	}
+
+	return 0;
+
+fail:
+	ubi_dump_ec_hdr(ec_hdr);
+	dump_stack();
+	return -EINVAL;
+}
+
+/**
+ * self_check_peb_ec_hdr - check erase counter header.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ *
+ * This function returns zero if the erase counter header is all right and and
+ * a negative error code if not or if an error occurred.
+ */
+static int self_check_peb_ec_hdr(const struct ubi_device *ubi, int pnum)
+{
+	int err;
+	uint32_t crc, hdr_crc;
+	struct ubi_ec_hdr *ec_hdr;
+
+	if (!ubi_dbg_chk_io(ubi))
+		return 0;
+
+	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
+	if (!ec_hdr)
+		return -ENOMEM;
+
+	err = ubi_io_read(ubi, ec_hdr, pnum, 0, UBI_EC_HDR_SIZE);
+	if (err && err != UBI_IO_BITFLIPS && !mtd_is_eccerr(err))
+		goto exit;
+
+	crc = crc32(UBI_CRC32_INIT, ec_hdr, UBI_EC_HDR_SIZE_CRC);
+	hdr_crc = be32_to_cpu(ec_hdr->hdr_crc);
+	if (hdr_crc != crc) {
+		ubi_err(ubi, "bad CRC, calculated %#08x, read %#08x",
+			crc, hdr_crc);
+		ubi_err(ubi, "self-check failed for PEB %d", pnum);
+		ubi_dump_ec_hdr(ec_hdr);
+		dump_stack();
+		err = -EINVAL;
+		goto exit;
+	}
+
+	err = self_check_ec_hdr(ubi, pnum, ec_hdr);
+
+exit:
+	kfree(ec_hdr);
+	return err;
+}
+
+/**
+ * self_check_vid_hdr - check that a volume identifier header is all right.
+ * @ubi: UBI device description object
+ * @pnum: physical eraseblock number the volume identifier header belongs to
+ * @vid_hdr: the volume identifier header to check
+ *
+ * This function returns zero if the volume identifier header is all right, and
+ * %-EINVAL if not.
+ */
+static int self_check_vid_hdr(const struct ubi_device *ubi, int pnum,
+			      const struct ubi_vid_hdr *vid_hdr)
+{
+	int err;
+	uint32_t magic;
+
+	if (!ubi_dbg_chk_io(ubi))
+		return 0;
+
+	magic = be32_to_cpu(vid_hdr->magic);
+	if (magic != UBI_VID_HDR_MAGIC) {
+		ubi_err(ubi, "bad VID header magic %#08x at PEB %d, must be %#08x",
+			magic, pnum, UBI_VID_HDR_MAGIC);
+		goto fail;
+	}
+
+	err = validate_vid_hdr(ubi, vid_hdr);
+	if (err) {
+		ubi_err(ubi, "self-check failed for PEB %d", pnum);
+		goto fail;
+	}
+
+	return err;
+
+fail:
+	ubi_err(ubi, "self-check failed for PEB %d", pnum);
+	ubi_dump_vid_hdr(vid_hdr);
+	dump_stack();
+	return -EINVAL;
+
+}
+
+/**
+ * self_check_peb_vid_hdr - check volume identifier header.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ *
+ * This function returns zero if the volume identifier header is all right,
+ * and a negative error code if not or if an error occurred.
+ */
+static int self_check_peb_vid_hdr(const struct ubi_device *ubi, int pnum)
+{
+	int err;
+	uint32_t crc, hdr_crc;
+	struct ubi_vid_io_buf *vidb;
+	struct ubi_vid_hdr *vid_hdr;
+	void *p;
+
+	if (!ubi_dbg_chk_io(ubi))
+		return 0;
+
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb)
+		return -ENOMEM;
+
+	vid_hdr = ubi_get_vid_hdr(vidb);
+	p = vidb->buffer;
+	err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
+			  ubi->vid_hdr_alsize);
+	if (err && err != UBI_IO_BITFLIPS && !mtd_is_eccerr(err))
+		goto exit;
+
+	crc = crc32(UBI_CRC32_INIT, vid_hdr, UBI_VID_HDR_SIZE_CRC);
+	hdr_crc = be32_to_cpu(vid_hdr->hdr_crc);
+	if (hdr_crc != crc) {
+		ubi_err(ubi, "bad VID header CRC at PEB %d, calculated %#08x, read %#08x",
+			pnum, crc, hdr_crc);
+		ubi_err(ubi, "self-check failed for PEB %d", pnum);
+		ubi_dump_vid_hdr(vid_hdr);
+		dump_stack();
+		err = -EINVAL;
+		goto exit;
+	}
+
+	err = self_check_vid_hdr(ubi, pnum, vid_hdr);
+
+exit:
+	ubi_free_vid_buf(vidb);
+	return err;
+}
+
+/**
+ * self_check_write - make sure write succeeded.
+ * @ubi: UBI device description object
+ * @buf: buffer with data which were written
+ * @pnum: physical eraseblock number the data were written to
+ * @offset: offset within the physical eraseblock the data were written to
+ * @len: how many bytes were written
+ *
+ * This functions reads data which were recently written and compares it with
+ * the original data buffer - the data have to match. Returns zero if the data
+ * match and a negative error code if not or in case of failure.
+ */
+static int self_check_write(struct ubi_device *ubi, const void *buf, int pnum,
+			    int offset, int len)
+{
+	int err, i;
+	size_t read;
+	void *buf1;
+	loff_t addr = (loff_t)pnum * ubi->peb_size + offset;
+
+	if (!ubi_dbg_chk_io(ubi))
+		return 0;
+
+	buf1 = __vmalloc(len, GFP_NOFS, PAGE_KERNEL);
+	if (!buf1) {
+		ubi_err(ubi, "cannot allocate memory to check writes");
+		return 0;
+	}
+
+	err = mtd_read(ubi->mtd, addr, len, &read, buf1);
+	if (err && !mtd_is_bitflip(err))
+		goto out_free;
+
+	for (i = 0; i < len; i++) {
+		uint8_t c = ((uint8_t *)buf)[i];
+		uint8_t c1 = ((uint8_t *)buf1)[i];
+		int dump_len;
+
+		if (c == c1)
+			continue;
+
+		ubi_err(ubi, "self-check failed for PEB %d:%d, len %d",
+			pnum, offset, len);
+		ubi_msg(ubi, "data differ at position %d", i);
+		dump_len = max_t(int, 128, len - i);
+		ubi_msg(ubi, "hex dump of the original buffer from %d to %d",
+			i, i + dump_len);
+		print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
+			       buf + i, dump_len, 1);
+		ubi_msg(ubi, "hex dump of the read buffer from %d to %d",
+			i, i + dump_len);
+		print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,
+			       buf1 + i, dump_len, 1);
+		dump_stack();
+		err = -EINVAL;
+		goto out_free;
+	}
+
+	vfree(buf1);
+	return 0;
+
+out_free:
+	vfree(buf1);
+	return err;
+}
+
+/**
+ * ubi_self_check_all_ff - check that a region of flash is empty.
+ * @ubi: UBI device description object
+ * @pnum: the physical eraseblock number to check
+ * @offset: the starting offset within the physical eraseblock to check
+ * @len: the length of the region to check
+ *
+ * This function returns zero if only 0xFF bytes are present at offset
+ * @offset of the physical eraseblock @pnum, and a negative error code if not
+ * or if an error occurred.
+ */
+int ubi_self_check_all_ff(struct ubi_device *ubi, int pnum, int offset, int len)
+{
+	size_t read;
+	int err;
+	void *buf;
+	loff_t addr = (loff_t)pnum * ubi->peb_size + offset;
+
+	if (!ubi_dbg_chk_io(ubi))
+		return 0;
+
+	buf = __vmalloc(len, GFP_NOFS, PAGE_KERNEL);
+	if (!buf) {
+		ubi_err(ubi, "cannot allocate memory to check for 0xFFs");
+		return 0;
+	}
+
+	err = mtd_read(ubi->mtd, addr, len, &read, buf);
+	if (err && !mtd_is_bitflip(err)) {
+		ubi_err(ubi, "err %d while reading %d bytes from PEB %d:%d, read %zd bytes",
+			err, len, pnum, offset, read);
+		goto error;
+	}
+
+	err = ubi_check_pattern(buf, 0xFF, len);
+	if (err == 0) {
+		ubi_err(ubi, "flash region at PEB %d:%d, length %d does not contain all 0xFF bytes",
+			pnum, offset, len);
+		goto fail;
+	}
+
+	vfree(buf);
+	return 0;
+
+fail:
+	ubi_err(ubi, "self-check failed for PEB %d", pnum);
+	ubi_msg(ubi, "hex dump of the %d-%d region", offset, offset + len);
+	print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1, buf, len, 1);
+	err = -EINVAL;
+error:
+	dump_stack();
+	vfree(buf);
+	return err;
+}