drivers/mtd/ubi/upd.c - arm/linux - Git at Google

 /*
  * Copyright (c) International Business Machines Corp., 2006
  * Copyright (c) Nokia Corporation, 2006
  *
  * 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)
  *
  * Jan 2007: Alexander Schmidt, hacked per-volume update.
  */

 /*
  * This file contains implementation of the volume update and atomic LEB change
  * functionality.
  *
  * The update operation is based on the per-volume update marker which is
  * stored in the volume table. The update marker is set before the update
  * starts, and removed after the update has been finished. So if the update was
  * interrupted by an unclean re-boot or due to some other reasons, the update
  * marker stays on the flash media and UBI finds it when it attaches the MTD
  * device next time. If the update marker is set for a volume, the volume is
  * treated as damaged and most I/O operations are prohibited. Only a new update
  * operation is allowed.
  *
  * Note, in general it is possible to implement the update operation as a
  * transaction with a roll-back capability.
  */

 #include <linux/err.h>
 #include <linux/uaccess.h>
 #include <linux/math64.h>
 #include "ubi.h"

 /**
  * set_update_marker - set update marker.
  * @ubi: UBI device description object
  * @vol: volume description object
  *
  * This function sets the update marker flag for volume @vol. Returns zero
  * in case of success and a negative error code in case of failure.
  */
 static int set_update_marker(struct ubi_device *ubi, struct ubi_volume *vol)
 {
 	int err;
 	struct ubi_vtbl_record vtbl_rec;

 	dbg_gen("set update marker for volume %d", vol->vol_id);

 	if (vol->upd_marker) {
 		ubi_assert(ubi->vtbl[vol->vol_id].upd_marker);
 		dbg_gen("already set");
 		return 0;
 	}

 	vtbl_rec = ubi->vtbl[vol->vol_id];
 	vtbl_rec.upd_marker = 1;

 	mutex_lock(&ubi->device_mutex);
 	err = ubi_change_vtbl_record(ubi, vol->vol_id, &vtbl_rec);
 	vol->upd_marker = 1;
 	mutex_unlock(&ubi->device_mutex);
 	return err;
 }

 /**
  * clear_update_marker - clear update marker.
  * @ubi: UBI device description object
  * @vol: volume description object
  * @bytes: new data size in bytes
  *
  * This function clears the update marker for volume @vol, sets new volume
  * data size and clears the "corrupted" flag (static volumes only). Returns
  * zero in case of success and a negative error code in case of failure.
  */
 static int clear_update_marker(struct ubi_device *ubi, struct ubi_volume *vol,
 			       long long bytes)
 {
 	int err;
 	struct ubi_vtbl_record vtbl_rec;

 	dbg_gen("clear update marker for volume %d", vol->vol_id);

 	vtbl_rec = ubi->vtbl[vol->vol_id];
 	ubi_assert(vol->upd_marker && vtbl_rec.upd_marker);
 	vtbl_rec.upd_marker = 0;

 	if (vol->vol_type == UBI_STATIC_VOLUME) {
 		vol->corrupted = 0;
 		vol->used_bytes = bytes;
 		vol->used_ebs = div_u64_rem(bytes, vol->usable_leb_size,
 					    &vol->last_eb_bytes);
 		if (vol->last_eb_bytes)
 			vol->used_ebs += 1;
 		else
 			vol->last_eb_bytes = vol->usable_leb_size;
 	}

 	mutex_lock(&ubi->device_mutex);
 	err = ubi_change_vtbl_record(ubi, vol->vol_id, &vtbl_rec);
 	vol->upd_marker = 0;
 	mutex_unlock(&ubi->device_mutex);
 	return err;
 }

 /**
  * ubi_start_update - start volume update.
  * @ubi: UBI device description object
  * @vol: volume description object
  * @bytes: update bytes
  *
  * This function starts volume update operation. If @bytes is zero, the volume
  * is just wiped out. Returns zero in case of success and a negative error code
  * in case of failure.
  */
 int ubi_start_update(struct ubi_device *ubi, struct ubi_volume *vol,
 		     long long bytes)
 {
 	int i, err;

 	dbg_gen("start update of volume %d, %llu bytes", vol->vol_id, bytes);
 	ubi_assert(!vol->updating && !vol->changing_leb);
 	vol->updating = 1;

 	vol->upd_buf = vmalloc(ubi->leb_size);
 	if (!vol->upd_buf)
 		return -ENOMEM;

 	err = set_update_marker(ubi, vol);
 	if (err)
 		return err;

 	/* Before updating - wipe out the volume */
 	for (i = 0; i < vol->reserved_pebs; i++) {
 		err = ubi_eba_unmap_leb(ubi, vol, i);
 		if (err)
 			return err;
 	}

 	if (bytes == 0) {
 		err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
 		if (err)
 			return err;

 		err = clear_update_marker(ubi, vol, 0);
 		if (err)
 			return err;

 		vfree(vol->upd_buf);
 		vol->updating = 0;
 		return 0;
 	}

 	vol->upd_ebs = div_u64(bytes + vol->usable_leb_size - 1,
 			       vol->usable_leb_size);
 	vol->upd_bytes = bytes;
 	vol->upd_received = 0;
 	return 0;
 }

 /**
  * ubi_start_leb_change - start atomic LEB change.
  * @ubi: UBI device description object
  * @vol: volume description object
  * @req: operation request
  *
  * This function starts atomic LEB change operation. Returns zero in case of
  * success and a negative error code in case of failure.
  */
 int ubi_start_leb_change(struct ubi_device *ubi, struct ubi_volume *vol,
 			 const struct ubi_leb_change_req *req)
 {
 	ubi_assert(!vol->updating && !vol->changing_leb);

 	dbg_gen("start changing LEB %d:%d, %u bytes",
 		vol->vol_id, req->lnum, req->bytes);
 	if (req->bytes == 0)
 		return ubi_eba_atomic_leb_change(ubi, vol, req->lnum, NULL, 0);

 	vol->upd_bytes = req->bytes;
 	vol->upd_received = 0;
 	vol->changing_leb = 1;
 	vol->ch_lnum = req->lnum;

 	vol->upd_buf = vmalloc(req->bytes);
 	if (!vol->upd_buf)
 		return -ENOMEM;

 	return 0;
 }

 /**
  * write_leb - write update data.
  * @ubi: UBI device description object
  * @vol: volume description object
  * @lnum: logical eraseblock number
  * @buf: data to write
  * @len: data size
  * @used_ebs: how many logical eraseblocks will this volume contain (static
  * volumes only)
  *
  * This function writes update data to corresponding logical eraseblock. In
  * case of dynamic volume, this function checks if the data contains 0xFF bytes
  * at the end. If yes, the 0xFF bytes are cut and not written. So if the whole
  * buffer contains only 0xFF bytes, the LEB is left unmapped.
  *
  * The reason why we skip the trailing 0xFF bytes in case of dynamic volume is
  * that we want to make sure that more data may be appended to the logical
  * eraseblock in future. Indeed, writing 0xFF bytes may have side effects and
  * this PEB won't be writable anymore. So if one writes the file-system image
  * to the UBI volume where 0xFFs mean free space - UBI makes sure this free
  * space is writable after the update.
  *
  * We do not do this for static volumes because they are read-only. But this
  * also cannot be done because we have to store per-LEB CRC and the correct
  * data length.
  *
  * This function returns zero in case of success and a negative error code in
  * case of failure.
  */
 static int write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		     void *buf, int len, int used_ebs)
 {
 	int err;

 	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
 		int l = ALIGN(len, ubi->min_io_size);

 		memset(buf + len, 0xFF, l - len);
 		len = ubi_calc_data_len(ubi, buf, l);
 		if (len == 0) {
 			dbg_gen("all %d bytes contain 0xFF - skip", len);
 			return 0;
 		}

 		err = ubi_eba_write_leb(ubi, vol, lnum, buf, 0, len);
 	} else {
 		/*
 		 * When writing static volume, and this is the last logical
 		 * eraseblock, the length (@len) does not have to be aligned to
 		 * the minimal flash I/O unit. The 'ubi_eba_write_leb_st()'
 		 * function accepts exact (unaligned) length and stores it in
 		 * the VID header. And it takes care of proper alignment by
 		 * padding the buffer. Here we just make sure the padding will
 		 * contain zeros, not random trash.
 		 */
 		memset(buf + len, 0, vol->usable_leb_size - len);
 		err = ubi_eba_write_leb_st(ubi, vol, lnum, buf, len, used_ebs);
 	}

 	return err;
 }

 /**
  * ubi_more_update_data - write more update data.
  * @ubi: UBI device description object
  * @vol: volume description object
  * @buf: write data (user-space memory buffer)
  * @count: how much bytes to write
  *
  * This function writes more data to the volume which is being updated. It may
  * be called arbitrary number of times until all the update data arriveis. This
  * function returns %0 in case of success, number of bytes written during the
  * last call if the whole volume update has been successfully finished, and a
  * negative error code in case of failure.
  */
 int ubi_more_update_data(struct ubi_device *ubi, struct ubi_volume *vol,
 			 const void __user *buf, int count)
 {
 	int lnum, offs, err = 0, len, to_write = count;

 	dbg_gen("write %d of %lld bytes, %lld already passed",
 		count, vol->upd_bytes, vol->upd_received);

 	if (ubi->ro_mode)
 		return -EROFS;

 	lnum = div_u64_rem(vol->upd_received,  vol->usable_leb_size, &offs);
 	if (vol->upd_received + count > vol->upd_bytes)
 		to_write = count = vol->upd_bytes - vol->upd_received;

 	/*
 	 * When updating volumes, we accumulate whole logical eraseblock of
 	 * data and write it at once.
 	 */
 	if (offs != 0) {
 		/*
 		 * This is a write to the middle of the logical eraseblock. We
 		 * copy the data to our update buffer and wait for more data or
 		 * flush it if the whole eraseblock is written or the update
 		 * is finished.
 		 */

 		len = vol->usable_leb_size - offs;
 		if (len > count)
 			len = count;

 		err = copy_from_user(vol->upd_buf + offs, buf, len);
 		if (err)
 			return -EFAULT;

 		if (offs + len == vol->usable_leb_size ||
 		    vol->upd_received + len == vol->upd_bytes) {
 			int flush_len = offs + len;

 			/*
 			 * OK, we gathered either the whole eraseblock or this
 			 * is the last chunk, it's time to flush the buffer.
 			 */
 			ubi_assert(flush_len <= vol->usable_leb_size);
 			err = write_leb(ubi, vol, lnum, vol->upd_buf, flush_len,
 					vol->upd_ebs);
 			if (err)
 				return err;
 		}

 		vol->upd_received += len;
 		count -= len;
 		buf += len;
 		lnum += 1;
 	}

 	/*
 	 * If we've got more to write, let's continue. At this point we know we
 	 * are starting from the beginning of an eraseblock.
 	 */
 	while (count) {
 		if (count > vol->usable_leb_size)
 			len = vol->usable_leb_size;
 		else
 			len = count;

 		err = copy_from_user(vol->upd_buf, buf, len);
 		if (err)
 			return -EFAULT;

 		if (len == vol->usable_leb_size ||
 		    vol->upd_received + len == vol->upd_bytes) {
 			err = write_leb(ubi, vol, lnum, vol->upd_buf,
 					len, vol->upd_ebs);
 			if (err)
 				break;
 		}

 		vol->upd_received += len;
 		count -= len;
 		lnum += 1;
 		buf += len;
 	}

 	ubi_assert(vol->upd_received <= vol->upd_bytes);
 	if (vol->upd_received == vol->upd_bytes) {
 		err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
 		if (err)
 			return err;
 		/* The update is finished, clear the update marker */
 		err = clear_update_marker(ubi, vol, vol->upd_bytes);
 		if (err)
 			return err;
 		vol->updating = 0;
 		err = to_write;
 		vfree(vol->upd_buf);
 	}

 	return err;
 }

 /**
  * ubi_more_leb_change_data - accept more data for atomic LEB change.
  * @ubi: UBI device description object
  * @vol: volume description object
  * @buf: write data (user-space memory buffer)
  * @count: how much bytes to write
  *
  * This function accepts more data to the volume which is being under the
  * "atomic LEB change" operation. It may be called arbitrary number of times
  * until all data arrives. This function returns %0 in case of success, number
  * of bytes written during the last call if the whole "atomic LEB change"
  * operation has been successfully finished, and a negative error code in case
  * of failure.
  */
 int ubi_more_leb_change_data(struct ubi_device *ubi, struct ubi_volume *vol,
 			     const void __user *buf, int count)
 {
 	int err;

 	dbg_gen("write %d of %lld bytes, %lld already passed",
 		count, vol->upd_bytes, vol->upd_received);

 	if (ubi->ro_mode)
 		return -EROFS;

 	if (vol->upd_received + count > vol->upd_bytes)
 		count = vol->upd_bytes - vol->upd_received;

 	err = copy_from_user(vol->upd_buf + vol->upd_received, buf, count);
 	if (err)
 		return -EFAULT;

 	vol->upd_received += count;

 	if (vol->upd_received == vol->upd_bytes) {
 		int len = ALIGN((int)vol->upd_bytes, ubi->min_io_size);

 		memset(vol->upd_buf + vol->upd_bytes, 0xFF,
 		       len - vol->upd_bytes);
 		len = ubi_calc_data_len(ubi, vol->upd_buf, len);
 		err = ubi_eba_atomic_leb_change(ubi, vol, vol->ch_lnum,
 						vol->upd_buf, len);
 		if (err)
 			return err;
 	}

 	ubi_assert(vol->upd_received <= vol->upd_bytes);
 	if (vol->upd_received == vol->upd_bytes) {
 		vol->changing_leb = 0;
 		err = count;
 		vfree(vol->upd_buf);
 	}

 	return err;
 }
	/*
	* Copyright (c) International Business Machines Corp., 2006
	* Copyright (c) Nokia Corporation, 2006
	*
	* 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)
	*
	* Jan 2007: Alexander Schmidt, hacked per-volume update.
	*/

	/*
	* This file contains implementation of the volume update and atomic LEB change
	* functionality.
	*
	* The update operation is based on the per-volume update marker which is
	* stored in the volume table. The update marker is set before the update
	* starts, and removed after the update has been finished. So if the update was
	* interrupted by an unclean re-boot or due to some other reasons, the update
	* marker stays on the flash media and UBI finds it when it attaches the MTD
	* device next time. If the update marker is set for a volume, the volume is
	* treated as damaged and most I/O operations are prohibited. Only a new update
	* operation is allowed.
	*
	* Note, in general it is possible to implement the update operation as a
	* transaction with a roll-back capability.
	*/

	#include <linux/err.h>
	#include <linux/uaccess.h>
	#include <linux/math64.h>
	#include "ubi.h"

	/**
	* set_update_marker - set update marker.
	* @ubi: UBI device description object
	* @vol: volume description object
	*
	* This function sets the update marker flag for volume @vol. Returns zero
	* in case of success and a negative error code in case of failure.
	*/
	static int set_update_marker(struct ubi_device ubi, struct ubi_volume vol)
	{
	int err;
	struct ubi_vtbl_record vtbl_rec;

	dbg_gen("set update marker for volume %d", vol->vol_id);

	if (vol->upd_marker) {
	ubi_assert(ubi->vtbl[vol->vol_id].upd_marker);
	dbg_gen("already set");
	return 0;
	}

	vtbl_rec = ubi->vtbl[vol->vol_id];
	vtbl_rec.upd_marker = 1;

	mutex_lock(&ubi->device_mutex);
	err = ubi_change_vtbl_record(ubi, vol->vol_id, &vtbl_rec);
	vol->upd_marker = 1;
	mutex_unlock(&ubi->device_mutex);
	return err;
	}

	/**
	* clear_update_marker - clear update marker.
	* @ubi: UBI device description object
	* @vol: volume description object
	* @bytes: new data size in bytes
	*
	* This function clears the update marker for volume @vol, sets new volume
	* data size and clears the "corrupted" flag (static volumes only). Returns
	* zero in case of success and a negative error code in case of failure.
	*/
	static int clear_update_marker(struct ubi_device ubi, struct ubi_volume vol,
	long long bytes)
	{
	int err;
	struct ubi_vtbl_record vtbl_rec;

	dbg_gen("clear update marker for volume %d", vol->vol_id);

	vtbl_rec = ubi->vtbl[vol->vol_id];
	ubi_assert(vol->upd_marker && vtbl_rec.upd_marker);
	vtbl_rec.upd_marker = 0;

	if (vol->vol_type == UBI_STATIC_VOLUME) {
	vol->corrupted = 0;
	vol->used_bytes = bytes;
	vol->used_ebs = div_u64_rem(bytes, vol->usable_leb_size,
	&vol->last_eb_bytes);
	if (vol->last_eb_bytes)
	vol->used_ebs += 1;
	else
	vol->last_eb_bytes = vol->usable_leb_size;
	}

	mutex_lock(&ubi->device_mutex);
	err = ubi_change_vtbl_record(ubi, vol->vol_id, &vtbl_rec);
	vol->upd_marker = 0;
	mutex_unlock(&ubi->device_mutex);
	return err;
	}

	/**
	* ubi_start_update - start volume update.
	* @ubi: UBI device description object
	* @vol: volume description object
	* @bytes: update bytes
	*
	* This function starts volume update operation. If @bytes is zero, the volume
	* is just wiped out. Returns zero in case of success and a negative error code
	* in case of failure.
	*/
	int ubi_start_update(struct ubi_device ubi, struct ubi_volume vol,
	long long bytes)
	{
	int i, err;

	dbg_gen("start update of volume %d, %llu bytes", vol->vol_id, bytes);
	ubi_assert(!vol->updating && !vol->changing_leb);
	vol->updating = 1;

	vol->upd_buf = vmalloc(ubi->leb_size);
	if (!vol->upd_buf)
	return -ENOMEM;

	err = set_update_marker(ubi, vol);
	if (err)
	return err;

	/* Before updating - wipe out the volume */
	for (i = 0; i < vol->reserved_pebs; i++) {
	err = ubi_eba_unmap_leb(ubi, vol, i);
	if (err)
	return err;
	}

	if (bytes == 0) {
	err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
	if (err)
	return err;

	err = clear_update_marker(ubi, vol, 0);
	if (err)
	return err;

	vfree(vol->upd_buf);
	vol->updating = 0;
	return 0;
	}

	vol->upd_ebs = div_u64(bytes + vol->usable_leb_size - 1,
	vol->usable_leb_size);
	vol->upd_bytes = bytes;
	vol->upd_received = 0;
	return 0;
	}

	/**
	* ubi_start_leb_change - start atomic LEB change.
	* @ubi: UBI device description object
	* @vol: volume description object
	* @req: operation request
	*
	* This function starts atomic LEB change operation. Returns zero in case of
	* success and a negative error code in case of failure.
	*/
	int ubi_start_leb_change(struct ubi_device ubi, struct ubi_volume vol,
	const struct ubi_leb_change_req *req)
	{
	ubi_assert(!vol->updating && !vol->changing_leb);

	dbg_gen("start changing LEB %d:%d, %u bytes",
	vol->vol_id, req->lnum, req->bytes);
	if (req->bytes == 0)
	return ubi_eba_atomic_leb_change(ubi, vol, req->lnum, NULL, 0);

	vol->upd_bytes = req->bytes;
	vol->upd_received = 0;
	vol->changing_leb = 1;
	vol->ch_lnum = req->lnum;

	vol->upd_buf = vmalloc(req->bytes);
	if (!vol->upd_buf)
	return -ENOMEM;

	return 0;
	}

	/**
	* write_leb - write update data.
	* @ubi: UBI device description object
	* @vol: volume description object
	* @lnum: logical eraseblock number
	* @buf: data to write
	* @len: data size
	* @used_ebs: how many logical eraseblocks will this volume contain (static
	* volumes only)
	*
	* This function writes update data to corresponding logical eraseblock. In
	* case of dynamic volume, this function checks if the data contains 0xFF bytes
	* at the end. If yes, the 0xFF bytes are cut and not written. So if the whole
	* buffer contains only 0xFF bytes, the LEB is left unmapped.
	*
	* The reason why we skip the trailing 0xFF bytes in case of dynamic volume is
	* that we want to make sure that more data may be appended to the logical
	* eraseblock in future. Indeed, writing 0xFF bytes may have side effects and
	* this PEB won't be writable anymore. So if one writes the file-system image
	* to the UBI volume where 0xFFs mean free space - UBI makes sure this free
	* space is writable after the update.
	*
	* We do not do this for static volumes because they are read-only. But this
	* also cannot be done because we have to store per-LEB CRC and the correct
	* data length.
	*
	* This function returns zero in case of success and a negative error code in
	* case of failure.
	*/
	static int write_leb(struct ubi_device ubi, struct ubi_volume vol, int lnum,
	void *buf, int len, int used_ebs)
	{
	int err;

	if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
	int l = ALIGN(len, ubi->min_io_size);

	memset(buf + len, 0xFF, l - len);
	len = ubi_calc_data_len(ubi, buf, l);
	if (len == 0) {
	dbg_gen("all %d bytes contain 0xFF - skip", len);
	return 0;
	}

	err = ubi_eba_write_leb(ubi, vol, lnum, buf, 0, len);
	} else {
	/*
	* When writing static volume, and this is the last logical
	* eraseblock, the length (@len) does not have to be aligned to
	* the minimal flash I/O unit. The 'ubi_eba_write_leb_st()'
	* function accepts exact (unaligned) length and stores it in
	* the VID header. And it takes care of proper alignment by
	* padding the buffer. Here we just make sure the padding will
	* contain zeros, not random trash.
	*/
	memset(buf + len, 0, vol->usable_leb_size - len);
	err = ubi_eba_write_leb_st(ubi, vol, lnum, buf, len, used_ebs);
	}

	return err;
	}

	/**
	* ubi_more_update_data - write more update data.
	* @ubi: UBI device description object
	* @vol: volume description object
	* @buf: write data (user-space memory buffer)
	* @count: how much bytes to write
	*
	* This function writes more data to the volume which is being updated. It may
	* be called arbitrary number of times until all the update data arriveis. This
	* function returns %0 in case of success, number of bytes written during the
	* last call if the whole volume update has been successfully finished, and a
	* negative error code in case of failure.
	*/
	int ubi_more_update_data(struct ubi_device ubi, struct ubi_volume vol,
	const void __user *buf, int count)
	{
	int lnum, offs, err = 0, len, to_write = count;

	dbg_gen("write %d of %lld bytes, %lld already passed",
	count, vol->upd_bytes, vol->upd_received);

	if (ubi->ro_mode)
	return -EROFS;

	lnum = div_u64_rem(vol->upd_received, vol->usable_leb_size, &offs);
	if (vol->upd_received + count > vol->upd_bytes)
	to_write = count = vol->upd_bytes - vol->upd_received;

	/*
	* When updating volumes, we accumulate whole logical eraseblock of
	* data and write it at once.
	*/
	if (offs != 0) {
	/*
	* This is a write to the middle of the logical eraseblock. We
	* copy the data to our update buffer and wait for more data or
	* flush it if the whole eraseblock is written or the update
	* is finished.
	*/

	len = vol->usable_leb_size - offs;
	if (len > count)
	len = count;

	err = copy_from_user(vol->upd_buf + offs, buf, len);
	if (err)
	return -EFAULT;

	if (offs + len == vol->usable_leb_size \|\|
	vol->upd_received + len == vol->upd_bytes) {
	int flush_len = offs + len;

	/*
	* OK, we gathered either the whole eraseblock or this
	* is the last chunk, it's time to flush the buffer.
	*/
	ubi_assert(flush_len <= vol->usable_leb_size);
	err = write_leb(ubi, vol, lnum, vol->upd_buf, flush_len,
	vol->upd_ebs);
	if (err)
	return err;
	}

	vol->upd_received += len;
	count -= len;
	buf += len;
	lnum += 1;
	}

	/*
	* If we've got more to write, let's continue. At this point we know we
	* are starting from the beginning of an eraseblock.
	*/
	while (count) {
	if (count > vol->usable_leb_size)
	len = vol->usable_leb_size;
	else
	len = count;

	err = copy_from_user(vol->upd_buf, buf, len);
	if (err)
	return -EFAULT;

	if (len == vol->usable_leb_size \|\|
	vol->upd_received + len == vol->upd_bytes) {
	err = write_leb(ubi, vol, lnum, vol->upd_buf,
	len, vol->upd_ebs);
	if (err)
	break;
	}

	vol->upd_received += len;
	count -= len;
	lnum += 1;
	buf += len;
	}

	ubi_assert(vol->upd_received <= vol->upd_bytes);
	if (vol->upd_received == vol->upd_bytes) {
	err = ubi_wl_flush(ubi, UBI_ALL, UBI_ALL);
	if (err)
	return err;
	/* The update is finished, clear the update marker */
	err = clear_update_marker(ubi, vol, vol->upd_bytes);
	if (err)
	return err;
	vol->updating = 0;
	err = to_write;
	vfree(vol->upd_buf);
	}

	return err;
	}

	/**
	* ubi_more_leb_change_data - accept more data for atomic LEB change.
	* @ubi: UBI device description object
	* @vol: volume description object
	* @buf: write data (user-space memory buffer)
	* @count: how much bytes to write
	*
	* This function accepts more data to the volume which is being under the
	* "atomic LEB change" operation. It may be called arbitrary number of times
	* until all data arrives. This function returns %0 in case of success, number
	* of bytes written during the last call if the whole "atomic LEB change"
	* operation has been successfully finished, and a negative error code in case
	* of failure.
	*/
	int ubi_more_leb_change_data(struct ubi_device ubi, struct ubi_volume vol,
	const void __user *buf, int count)
	{
	int err;

	dbg_gen("write %d of %lld bytes, %lld already passed",
	count, vol->upd_bytes, vol->upd_received);

	if (ubi->ro_mode)
	return -EROFS;

	if (vol->upd_received + count > vol->upd_bytes)
	count = vol->upd_bytes - vol->upd_received;

	err = copy_from_user(vol->upd_buf + vol->upd_received, buf, count);
	if (err)
	return -EFAULT;

	vol->upd_received += count;

	if (vol->upd_received == vol->upd_bytes) {
	int len = ALIGN((int)vol->upd_bytes, ubi->min_io_size);

	memset(vol->upd_buf + vol->upd_bytes, 0xFF,
	len - vol->upd_bytes);
	len = ubi_calc_data_len(ubi, vol->upd_buf, len);
	err = ubi_eba_atomic_leb_change(ubi, vol, vol->ch_lnum,
	vol->upd_buf, len);
	if (err)
	return err;
	}

	ubi_assert(vol->upd_received <= vol->upd_bytes);
	if (vol->upd_received == vol->upd_bytes) {
	vol->changing_leb = 0;
	err = count;
	vfree(vol->upd_buf);
	}

	return err;
	}