/**
 * 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;
}

/**
 * ubi_leb_map - map logical eraseblock to a physical eraseblock.
 * @desc: volume descriptor
 * @lnum: logical eraseblock number
 *
 * This function maps an un-mapped logical eraseblock @lnum to a physical
 * eraseblock. This means, that after a successful invocation of this
 * function the logical eraseblock @lnum will be empty (contain only %0xFF
 * bytes) and be mapped to a physical eraseblock, even if an unclean reboot
 * happens.
 *
 * This function returns zero in case of success, %-EBADF if the volume is
 * damaged because of an interrupted update, %-EBADMSG if the logical
 * eraseblock is already mapped, and other negative error codes in case of
 * other failures.
 */
int ubi_leb_map(struct ubi_volume_desc *desc, int lnum)
{
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;

	dbg_gen("unmap LEB %d:%d", vol->vol_id, lnum);

	if (desc->mode == UBI_READONLY || vol->vol_type == UBI_STATIC_VOLUME)
		return -EROFS;

	if (lnum < 0 || lnum >= vol->reserved_pebs)
		return -EINVAL;

	if (vol->upd_marker)
		return -EBADF;

	if (vol->eba_tbl[lnum] >= 0)
		return -EBADMSG;

	return ubi_eba_write_leb(ubi, vol, lnum, NULL, 0, 0);
}

/**
 * ubi_leb_map - map logical eraseblock to a physical eraseblock.
 * @desc: volume descriptor
 * @lnum: logical eraseblock number
 *
 * This function maps an un-mapped logical eraseblock @lnum to a physical
 * eraseblock. This means, that after a successful invocation of this
 * function the logical eraseblock @lnum will be empty (contain only %0xFF
 * bytes) and be mapped to a physical eraseblock, even if an unclean reboot
 * happens.
 *
 * This function returns zero in case of success, %-EBADF if the volume is
 * damaged because of an interrupted update, %-EBADMSG if the logical
 * eraseblock is already mapped, and other negative error codes in case of
 * other failures.
 */
int ubi_leb_map(struct ubi_volume_desc *desc, int lnum)
{
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;

	dbg_gen("map LEB %d:%d", vol->vol_id, lnum);

	if (desc->mode == UBI_READONLY || vol->vol_type == UBI_STATIC_VOLUME)
		return -EROFS;

	if (!ubi_leb_valid(vol, lnum))
		return -EINVAL;

	if (vol->upd_marker)
		return -EBADF;

	if (ubi_eba_is_mapped(vol, lnum))
		return -EBADMSG;

	return ubi_eba_write_leb(ubi, vol, lnum, NULL, 0, 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;
}

/**
 * ubi_create_gluebi - initialize gluebi for an UBI volume.
 * @ubi: UBI device description object
 * @vol: volume description object
 *
 * This function is called when an UBI volume is created in order to create
 * corresponding fake MTD device. Returns zero in case of success and a
 * negative error code in case of failure.
 */
int ubi_create_gluebi(struct ubi_device *ubi, struct ubi_volume *vol)
{
	struct mtd_info *mtd = &vol->gluebi_mtd;

	mtd->name = kmemdup(vol->name, vol->name_len + 1, GFP_KERNEL);
	if (!mtd->name)
		return -ENOMEM;

	mtd->type = MTD_UBIVOLUME;
	if (!ubi->ro_mode)
		mtd->flags = MTD_WRITEABLE;
	mtd->writesize  = ubi->min_io_size;
	mtd->owner      = THIS_MODULE;
	mtd->erasesize  = vol->usable_leb_size;
	mtd->read       = gluebi_read;
	mtd->write      = gluebi_write;
	mtd->erase      = gluebi_erase;
	mtd->get_device = gluebi_get_device;
	mtd->put_device = gluebi_put_device;

	/*
	 * In case of dynamic volume, MTD device size is just volume size. In
	 * case of a static volume the size is equivalent to the amount of data
	 * bytes.
	 */
	if (vol->vol_type == UBI_DYNAMIC_VOLUME)
		mtd->size = (long long)vol->usable_leb_size * vol->reserved_pebs;
	else
		mtd->size = vol->used_bytes;

	if (add_mtd_device(mtd)) {
		ubi_err("cannot not add MTD device");
		kfree(mtd->name);
		return -ENFILE;
	}

	dbg_gen("added mtd%d (\"%s\"), size %llu, EB size %u",
		mtd->index, mtd->name, (unsigned long long)mtd->size, mtd->erasesize);
	return 0;
}

/**
 * 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;

	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 = clear_update_marker(ubi, vol, 0);
		if (err)
			return err;
		err = ubi_wl_flush(ubi);
		if (!err)
			vol->updating = 0;
	}

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

	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;
}

/**
 * compr_init - initialize a compressor.
 * @compr: compressor description object
 *
 * This function initializes the requested compressor and returns zero in case
 * of success or a negative error code in case of failure.
 */
static int __init compr_init(struct ubifs_compressor *compr)
{
	ubifs_compressors[compr->compr_type] = compr;

#ifdef CONFIG_NEEDS_MANUAL_RELOC
	ubifs_compressors[compr->compr_type]->name += gd->reloc_off;
	ubifs_compressors[compr->compr_type]->capi_name += gd->reloc_off;
	ubifs_compressors[compr->compr_type]->decompress += gd->reloc_off;
#endif

	if (compr->capi_name) {
		compr->cc = crypto_alloc_comp(compr->capi_name, 0, 0);
		if (IS_ERR(compr->cc)) {
			dbg_gen("cannot initialize compressor %s,"
				  " error %ld", compr->name,
				  PTR_ERR(compr->cc));
			return PTR_ERR(compr->cc);
		}
	}

	return 0;
}

/**
 * ubifs_umount - un-mount UBIFS file-system.
 * @c: UBIFS file-system description object
 *
 * Note, this function is called to free allocated resourced when un-mounting,
 * as well as free resources when an error occurred while we were half way
 * through mounting (error path cleanup function). So it has to make sure the
 * resource was actually allocated before freeing it.
 */
void ubifs_umount(struct ubifs_info *c)
{
	dbg_gen("un-mounting UBI device %d, volume %d", c->vi.ubi_num,
		c->vi.vol_id);

	spin_lock(&ubifs_infos_lock);
	list_del(&c->infos_list);
	spin_unlock(&ubifs_infos_lock);

	if (c->bgt)
		kthread_stop(c->bgt);

	free_orphans(c);
	ubifs_lpt_free(c, 0);

	kfree(c->cbuf);
	kfree(c->rcvrd_mst_node);
	kfree(c->mst_node);
	vfree(c->ileb_buf);
	vfree(c->sbuf);
	kfree(c->bottom_up_buf);
	ubifs_debugging_exit(c);
}

/**
 * ubi_leb_erase - erase logical eraseblock.
 * @desc: volume descriptor
 * @lnum: logical eraseblock number
 *
 * This function un-maps logical eraseblock @lnum and synchronously erases the
 * correspondent physical eraseblock. Returns zero in case of success and a
 * negative error code in case of failure.
 *
 * If the volume is damaged because of an interrupted update this function just
 * returns immediately with %-EBADF code.
 */
int ubi_leb_erase(struct ubi_volume_desc *desc, int lnum)
{
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	int err;

	dbg_gen("erase LEB %d:%d", vol->vol_id, lnum);

	if (desc->mode == UBI_READONLY || vol->vol_type == UBI_STATIC_VOLUME)
		return -EROFS;

	if (lnum < 0 || lnum >= vol->reserved_pebs)
		return -EINVAL;

	if (vol->upd_marker)
		return -EBADF;

	err = ubi_eba_unmap_leb(ubi, vol, lnum);
	if (err)
		return err;

	return ubi_wl_flush(ubi);
}

/**
 * gluebi_read - read operation of emulated MTD devices.
 * @mtd: MTD device description object
 * @from: absolute offset from where to read
 * @len: how many bytes to read
 * @retlen: count of read bytes is returned here
 * @buf: buffer to store the read data
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
		       size_t *retlen, unsigned char *buf)
{
	int err = 0, lnum, offs, total_read;
	struct ubi_volume *vol;
	struct ubi_device *ubi;

	dbg_gen("read %zd bytes from offset %lld", len, from);

	if (len < 0 || from < 0 || from + len > mtd->size)
		return -EINVAL;

	vol = container_of(mtd, struct ubi_volume, gluebi_mtd);
	ubi = vol->ubi;

	lnum = div_u64_rem(from, mtd->erasesize, &offs);
	total_read = len;
	while (total_read) {
		size_t to_read = mtd->erasesize - offs;

		if (to_read > total_read)
			to_read = total_read;

		err = ubi_eba_read_leb(ubi, vol, lnum, buf, offs, to_read, 0);
		if (err)
			break;

		lnum += 1;
		offs = 0;
		total_read -= to_read;
		buf += to_read;
	}

	*retlen = len - total_read;
	return err;
}

/**
 * ubi_open_volume_path - open UBI volume by its character device node path.
 * @pathname: volume character device node path
 * @mode: open mode
 *
 * This function is similar to 'ubi_open_volume()', but opens a volume the path
 * to its character device node.
 */
struct ubi_volume_desc *ubi_open_volume_path(const char *pathname, int mode)
{
	int error, ubi_num, vol_id;
	struct kstat stat;

	dbg_gen("open volume %s, mode %d", pathname, mode);

	if (!pathname || !*pathname)
		return ERR_PTR(-EINVAL);

	error = vfs_stat(pathname, &stat);
	if (error)
		return ERR_PTR(error);

	if (!S_ISCHR(stat.mode))
		return ERR_PTR(-EINVAL);

	ubi_num = ubi_major2num(MAJOR(stat.rdev));
	vol_id = MINOR(stat.rdev) - 1;

	if (vol_id >= 0 && ubi_num >= 0)
		return ubi_open_volume(ubi_num, vol_id, mode);
	return ERR_PTR(-ENODEV);
}

/**
 * ubi_leb_read_sg - read data into a scatter gather list.
 * @desc: volume descriptor
 * @lnum: logical eraseblock number to read from
 * @buf: buffer where to store the read data
 * @offset: offset within the logical eraseblock to read from
 * @len: how many bytes to read
 * @check: whether UBI has to check the read data's CRC or not.
 *
 * This function works exactly like ubi_leb_read_sg(). But instead of
 * storing the read data into a buffer it writes to an UBI scatter gather
 * list.
 */
int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
		    int offset, int len, int check)
{
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	int err, vol_id = vol->vol_id;

	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);

	err = leb_read_sanity_check(desc, lnum, offset, len);
	if (err < 0)
		return err;

	if (len == 0)
		return 0;

	err = ubi_eba_read_leb_sg(ubi, vol, sgl, lnum, offset, len, check);
	if (err && mtd_is_eccerr(err) && vol->vol_type == UBI_STATIC_VOLUME) {
		ubi_warn(ubi, "mark volume %d as corrupted", vol_id);
		vol->corrupted = 1;
	}

	return err;
}

/**
 * ubi_leb_read - read data.
 * @desc: volume descriptor
 * @lnum: logical eraseblock number to read from
 * @buf: buffer where to store the read data
 * @offset: offset within the logical eraseblock to read from
 * @len: how many bytes to read
 * @check: whether UBI has to check the read data's CRC or not.
 *
 * This function reads data from offset @offset of logical eraseblock @lnum and
 * stores the data at @buf. When reading from static volumes, @check specifies
 * whether the data has to be checked or not. If yes, the whole logical
 * eraseblock will be read and its CRC checksum will be checked (i.e., the CRC
 * checksum is per-eraseblock). So checking may substantially slow down the
 * read speed. The @check argument is ignored for dynamic volumes.
 *
 * In case of success, this function returns zero. In case of failure, this
 * function returns a negative error code.
 *
 * %-EBADMSG error code is returned:
 * o for both static and dynamic volumes if MTD driver has detected a data
 *   integrity problem (unrecoverable ECC checksum mismatch in case of NAND);
 * o for static volumes in case of data CRC mismatch.
 *
 * If the volume is damaged because of an interrupted update this function just
 * returns immediately with %-EBADF error code.
 */
int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
		 int len, int check)
{
	struct ubi_volume *vol = desc->vol;
	struct ubi_device *ubi = vol->ubi;
	int err, vol_id = vol->vol_id;

	dbg_gen("read %d bytes from LEB %d:%d:%d", len, vol_id, lnum, offset);

	if (vol_id < 0 || vol_id >= ubi->vtbl_slots || lnum < 0 ||
	    lnum >= vol->used_ebs || offset < 0 || len < 0 ||
	    offset + len > vol->usable_leb_size)
		return -EINVAL;

	if (vol->vol_type == UBI_STATIC_VOLUME) {
		if (vol->used_ebs == 0)
			/* Empty static UBI volume */
			return 0;
		if (lnum == vol->used_ebs - 1 &&
		    offset + len > vol->last_eb_bytes)
			return -EINVAL;
	}

	if (vol->upd_marker)
		return -EBADF;
	if (len == 0)
		return 0;

	err = ubi_eba_read_leb(ubi, vol, lnum, buf, offset, len, check);
	if (err && err == -EBADMSG && vol->vol_type == UBI_STATIC_VOLUME) {
		ubi_warn("mark volume %d as corrupted", vol_id);
		vol->corrupted = 1;
	}

	return err;
}

static int do_readpage(struct ubifs_info *c, struct inode *inode,
		       struct page *page, int last_block_size)
{
	void *addr;
	int err = 0, i;
	unsigned int block, beyond;
	struct ubifs_data_node *dn;
	loff_t i_size = inode->i_size;

	dbg_gen("ino %lu, pg %lu, i_size %lld",
		inode->i_ino, page->index, i_size);

	addr = kmap(page);

	block = page->index << UBIFS_BLOCKS_PER_PAGE_SHIFT;
	beyond = (i_size + UBIFS_BLOCK_SIZE - 1) >> UBIFS_BLOCK_SHIFT;
	if (block >= beyond) {
		/* Reading beyond inode */
		memset(addr, 0, PAGE_CACHE_SIZE);
		goto out;
	}

	dn = kmalloc(UBIFS_MAX_DATA_NODE_SZ, GFP_NOFS);
	if (!dn)
		return -ENOMEM;

	i = 0;
	while (1) {
		int ret;

		if (block >= beyond) {
			/* Reading beyond inode */
			err = -ENOENT;
			memset(addr, 0, UBIFS_BLOCK_SIZE);
		} else {
			/*
			 * Reading last block? Make sure to not write beyond
			 * the requested size in the destination buffer.
			 */
			if (((block + 1) == beyond) || last_block_size) {
				void *buff;
				int dlen;

				/*
				 * We need to buffer the data locally for the
				 * last block. This is to not pad the
				 * destination area to a multiple of
				 * UBIFS_BLOCK_SIZE.
				 */
				buff = malloc(UBIFS_BLOCK_SIZE);
				if (!buff) {
					printf("%s: Error, malloc fails!\n",
					       __func__);
					err = -ENOMEM;
					break;
				}

				/* Read block-size into temp buffer */
				ret = read_block(inode, buff, block, dn);
				if (ret) {
					err = ret;
					if (err != -ENOENT) {
						free(buff);
						break;
					}
				}

				if (last_block_size)
					dlen = last_block_size;
				else
					dlen = le32_to_cpu(dn->size);

				/* Now copy required size back to dest */
				memcpy(addr, buff, dlen);

				free(buff);
			} else {
				ret = read_block(inode, addr, block, dn);
				if (ret) {
					err = ret;
					if (err != -ENOENT)
						break;
				}
			}
		}
		if (++i >= UBIFS_BLOCKS_PER_PAGE)
			break;
		block += 1;
		addr += UBIFS_BLOCK_SIZE;
	}
	if (err) {
		if (err == -ENOENT) {
			/* Not found, so it must be a hole */
			dbg_gen("hole");
			goto out_free;
		}
		ubifs_err("cannot read page %lu of inode %lu, error %d",
			  page->index, inode->i_ino, err);
		goto error;
	}
//.........这里部分代码省略.........

static int ubifs_finddir(struct super_block *sb, char *dirname,
			 unsigned long root_inum, unsigned long *inum)
{
	int err;
	struct qstr nm;
	union ubifs_key key;
	struct ubifs_dent_node *dent;
	struct ubifs_info *c;
	struct file *file;
	struct dentry *dentry;
	struct inode *dir;

	file = kzalloc(sizeof(struct file), 0);
	dentry = kzalloc(sizeof(struct dentry), 0);
	dir = kzalloc(sizeof(struct inode), 0);
	if (!file || !dentry || !dir) {
		printf("%s: Error, no memory for malloc!\n", __func__);
		err = -ENOMEM;
		goto out;
	}

	dir->i_sb = sb;
	file->f_path.dentry = dentry;
	file->f_path.dentry->d_parent = dentry;
	file->f_path.dentry->d_inode = dir;
	file->f_path.dentry->d_inode->i_ino = root_inum;
	c = sb->s_fs_info;

	dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, file->f_pos);

	/* Find the first entry in TNC and save it */
	lowest_dent_key(c, &key, dir->i_ino);
	nm.name = NULL;
	dent = ubifs_tnc_next_ent(c, &key, &nm);
	if (IS_ERR(dent)) {
		err = PTR_ERR(dent);
		goto out;
	}

	file->f_pos = key_hash_flash(c, &dent->key);
	file->private_data = dent;

	while (1) {
		dbg_gen("feed '%s', ino %llu, new f_pos %#x",
			dent->name, (unsigned long long)le64_to_cpu(dent->inum),
			key_hash_flash(c, &dent->key));
		ubifs_assert(le64_to_cpu(dent->ch.sqnum) > ubifs_inode(dir)->creat_sqnum);

		nm.len = le16_to_cpu(dent->nlen);
		if ((strncmp(dirname, (char *)dent->name, nm.len) == 0) &&
		    (strlen(dirname) == nm.len)) {
			*inum = le64_to_cpu(dent->inum);
			return 1;
		}

		/* Switch to the next entry */
		key_read(c, &dent->key, &key);
		nm.name = (char *)dent->name;
		dent = ubifs_tnc_next_ent(c, &key, &nm);
		if (IS_ERR(dent)) {
			err = PTR_ERR(dent);
			goto out;
		}

		kfree(file->private_data);
		file->f_pos = key_hash_flash(c, &dent->key);
		file->private_data = dent;
		cond_resched();
	}

out:
	if (err != -ENOENT) {
		ubifs_err("cannot find next direntry, error %d", err);
		return err;
	}

	if (file)
		free(file);
	if (dentry)
		free(dentry);
	if (dir)
		free(dir);

	if (file->private_data)
		kfree(file->private_data);
	file->private_data = NULL;
	file->f_pos = 2;
	return 0;
}

static int ubifs_printdir(struct file *file, void *dirent)
{
	int err, over = 0;
	struct qstr nm;
	union ubifs_key key;
	struct ubifs_dent_node *dent;
	struct inode *dir = file->f_path.dentry->d_inode;
	struct ubifs_info *c = dir->i_sb->s_fs_info;

	dbg_gen("dir ino %lu, f_pos %#llx", dir->i_ino, file->f_pos);

	if (file->f_pos > UBIFS_S_KEY_HASH_MASK || file->f_pos == 2)
		/*
		 * The directory was seek'ed to a senseless position or there
		 * are no more entries.
		 */
		return 0;

	if (file->f_pos == 1) {
		/* Find the first entry in TNC and save it */
		lowest_dent_key(c, &key, dir->i_ino);
		nm.name = NULL;
		dent = ubifs_tnc_next_ent(c, &key, &nm);
		if (IS_ERR(dent)) {
			err = PTR_ERR(dent);
			goto out;
		}

		file->f_pos = key_hash_flash(c, &dent->key);
		file->private_data = dent;
	}

	dent = file->private_data;
	if (!dent) {
		/*
		 * The directory was seek'ed to and is now readdir'ed.
		 * Find the entry corresponding to @file->f_pos or the
		 * closest one.
		 */
		dent_key_init_hash(c, &key, dir->i_ino, file->f_pos);
		nm.name = NULL;
		dent = ubifs_tnc_next_ent(c, &key, &nm);
		if (IS_ERR(dent)) {
			err = PTR_ERR(dent);
			goto out;
		}
		file->f_pos = key_hash_flash(c, &dent->key);
		file->private_data = dent;
	}

	while (1) {
		dbg_gen("feed '%s', ino %llu, new f_pos %#x",
			dent->name, (unsigned long long)le64_to_cpu(dent->inum),
			key_hash_flash(c, &dent->key));
		ubifs_assert(le64_to_cpu(dent->ch.sqnum) > ubifs_inode(dir)->creat_sqnum);

		nm.len = le16_to_cpu(dent->nlen);
		over = filldir(c, (char *)dent->name, nm.len,
			       le64_to_cpu(dent->inum), dent->type);
		if (over)
			return 0;

		/* Switch to the next entry */
		key_read(c, &dent->key, &key);
		nm.name = (char *)dent->name;
		dent = ubifs_tnc_next_ent(c, &key, &nm);
		if (IS_ERR(dent)) {
			err = PTR_ERR(dent);
			goto out;
		}

		kfree(file->private_data);
		file->f_pos = key_hash_flash(c, &dent->key);
		file->private_data = dent;
		cond_resched();
	}

out:
	if (err != -ENOENT) {
		ubifs_err("cannot find next direntry, error %d", err);
		return err;
	}

	kfree(file->private_data);
	file->private_data = NULL;
	file->f_pos = 2;
	return 0;
}

struct inode *ubifs_iget(struct super_block *sb, unsigned long inum)
{
	int err;
	union ubifs_key key;
	struct ubifs_ino_node *ino;
	struct ubifs_info *c = sb->s_fs_info;
	struct inode *inode;
	struct ubifs_inode *ui;
	int i;

	dbg_gen("inode %lu", inum);

	/*
	 * U-Boot special handling of locked down inodes via recovery
	 * e.g. ubifs_recover_size()
	 */
	for (i = 0; i < INODE_LOCKED_MAX; i++) {
		/*
		 * Exit on last entry (NULL), inode not found in list
		 */
		if (inodes_locked_down[i] == NULL)
			break;

		if (inodes_locked_down[i]->i_ino == inum) {
			/*
			 * We found the locked down inode in our array,
			 * so just return this pointer instead of creating
			 * a new one.
			 */
			return inodes_locked_down[i];
		}
	}

	inode = iget_locked(sb, inum);
	if (!inode)
		return ERR_PTR(-ENOMEM);
	if (!(inode->i_state & I_NEW))
		return inode;
	ui = ubifs_inode(inode);

	ino = kmalloc(UBIFS_MAX_INO_NODE_SZ, GFP_NOFS);
	if (!ino) {
		err = -ENOMEM;
		goto out;
	}

	ino_key_init(c, &key, inode->i_ino);

	err = ubifs_tnc_lookup(c, &key, ino);
	if (err)
		goto out_ino;

	inode->i_flags |= (S_NOCMTIME | S_NOATIME);
	inode->i_nlink = le32_to_cpu(ino->nlink);
	inode->i_uid   = le32_to_cpu(ino->uid);
	inode->i_gid   = le32_to_cpu(ino->gid);
	inode->i_atime.tv_sec  = (int64_t)le64_to_cpu(ino->atime_sec);
	inode->i_atime.tv_nsec = le32_to_cpu(ino->atime_nsec);
	inode->i_mtime.tv_sec  = (int64_t)le64_to_cpu(ino->mtime_sec);
	inode->i_mtime.tv_nsec = le32_to_cpu(ino->mtime_nsec);
	inode->i_ctime.tv_sec  = (int64_t)le64_to_cpu(ino->ctime_sec);
	inode->i_ctime.tv_nsec = le32_to_cpu(ino->ctime_nsec);
	inode->i_mode = le32_to_cpu(ino->mode);
	inode->i_size = le64_to_cpu(ino->size);

	ui->data_len    = le32_to_cpu(ino->data_len);
	ui->flags       = le32_to_cpu(ino->flags);
	ui->compr_type  = le16_to_cpu(ino->compr_type);
	ui->creat_sqnum = le64_to_cpu(ino->creat_sqnum);
	ui->synced_i_size = ui->ui_size = inode->i_size;

	err = validate_inode(c, inode);
	if (err)
		goto out_invalid;

	if ((inode->i_mode & S_IFMT) == S_IFLNK) {
		if (ui->data_len <= 0 || ui->data_len > UBIFS_MAX_INO_DATA) {
			err = 12;
			goto out_invalid;
		}
		ui->data = kmalloc(ui->data_len + 1, GFP_NOFS);
		if (!ui->data) {
			err = -ENOMEM;
			goto out_ino;
		}
		memcpy(ui->data, ino->data, ui->data_len);
		((char *)ui->data)[ui->data_len] = '\0';
	}

	kfree(ino);
	inode->i_state &= ~(I_LOCK | I_NEW);
	return inode;

out_invalid:
	ubifs_err("inode %lu validation failed, error %d", inode->i_ino, err);
	dbg_dump_node(c, ino);
	dbg_dump_inode(c, inode);
	err = -EINVAL;
out_ino:
	kfree(ino);
//.........这里部分代码省略.........

/**
 * 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 = paranoid_check_not_bad(ubi, pnum);
	if (err)
		return err;

	addr = (loff_t)pnum * ubi->peb_size + offset;
retry:
	err = ubi->mtd->read(ubi->mtd, addr, len, &read, buf);
	if (err == -EUCLEAN)	err = 0;	//added by Elvis, for ignore EUCLEAN
	if (err) {
		if (err == -EUCLEAN) {
			/*
			 * -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.
			 */
			dbg_msg("fixable bit-flip detected at PEB %d", pnum);
			ubi_assert(len == read);
			return UBI_IO_BITFLIPS;
		}

		if (read != len && retries++ < UBI_IO_RETRIES) {
			dbg_io("error %d while reading %d bytes from PEB %d:%d,"
			       " read only %zd bytes, retry",
			       err, len, pnum, offset, read);
			yield();
			goto retry;
		}

		ubi_err("error %d while reading %d bytes from PEB %d:%d, "
			"read %zd bytes", err, len, pnum, offset, read);
		ubi_dbg_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 && err == -EBADMSG) {
			ubi_assert(0);
			err = -EIO;
		}
	} else {
		ubi_assert(len == read);

		if (ubi_dbg_is_bitflip()) {
			dbg_gen("bit-flip (emulated)");
			err = UBI_IO_BITFLIPS;
		}
	}

	return err;
}

/**
 * ubi_open_volume - open UBI volume.
 * @ubi_num: UBI device number
 * @vol_id: volume ID
 * @mode: open mode
 *
 * The @mode parameter specifies if the volume should be opened in read-only
 * mode, read-write mode, or exclusive mode. The exclusive mode guarantees that
 * nobody else will be able to open this volume. UBI allows to have many volume
 * readers and one writer at a time.
 *
 * If a static volume is being opened for the first time since boot, it will be
 * checked by this function, which means it will be fully read and the CRC
 * checksum of each logical eraseblock will be checked.
 *
 * This function returns volume descriptor in case of success and a negative
 * error code in case of failure.
 */
struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode)
{
	int err;
	struct ubi_volume_desc *desc;
	struct ubi_device *ubi;
	struct ubi_volume *vol;

	dbg_gen("open device %d, volume %d, mode %d", ubi_num, vol_id, mode);

	if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES)
		return ERR_PTR(-EINVAL);

	if (mode != UBI_READONLY && mode != UBI_READWRITE &&
	    mode != UBI_EXCLUSIVE)
		return ERR_PTR(-EINVAL);

	/*
	 * First of all, we have to get the UBI device to prevent its removal.
	 */
	ubi = ubi_get_device(ubi_num);
	if (!ubi)
		return ERR_PTR(-ENODEV);

	if (vol_id < 0 || vol_id >= ubi->vtbl_slots) {
		err = -EINVAL;
		goto out_put_ubi;
	}

	desc = kmalloc(sizeof(struct ubi_volume_desc), GFP_KERNEL);
	if (!desc) {
		err = -ENOMEM;
		goto out_put_ubi;
	}

	err = -ENODEV;
	if (!try_module_get(THIS_MODULE))
		goto out_free;

	spin_lock(&ubi->volumes_lock);
	vol = ubi->volumes[vol_id];
	if (!vol)
		goto out_unlock;

	err = -EBUSY;
	switch (mode) {
	case UBI_READONLY:
		if (vol->exclusive)
			goto out_unlock;
		vol->readers += 1;
		break;

	case UBI_READWRITE:
		if (vol->exclusive || vol->writers > 0)
			goto out_unlock;
		vol->writers += 1;
		break;

	case UBI_EXCLUSIVE:
		if (vol->exclusive || vol->writers || vol->readers)
			goto out_unlock;
		vol->exclusive = 1;
		break;
	}
	get_device(&vol->dev);
	vol->ref_count += 1;
	spin_unlock(&ubi->volumes_lock);

	desc->vol = vol;
	desc->mode = mode;

	mutex_lock(&ubi->ckvol_mutex);
	if (!vol->checked) {
		/* This is the first open - check the volume */
		err = ubi_check_volume(ubi, vol_id);
		if (err < 0) {
			mutex_unlock(&ubi->ckvol_mutex);
			ubi_close_volume(desc);
			return ERR_PTR(err);
		}
		if (err == 1) {
			ubi_warn("volume %d on UBI device %d is corrupted",
				 vol_id, ubi->ubi_num);
//.........这里部分代码省略.........

static struct dentry *ubifs_lookup(struct inode *dir, struct dentry *dentry,
				   struct nameidata *nd)
{
	int err;
	union ubifs_key key;
	struct inode *inode = NULL;
	struct ubifs_dent_node *dent;
	struct ubifs_info *c = dir->i_sb->s_fs_info;

	dbg_gen("'%.*s' in dir ino %lu",
		dentry->d_name.len, dentry->d_name.name, dir->i_ino);

	if (dentry->d_name.len > UBIFS_MAX_NLEN)
		return ERR_PTR(-ENAMETOOLONG);

	dent = kmalloc(UBIFS_MAX_DENT_NODE_SZ, GFP_NOFS);
	if (!dent)
		return ERR_PTR(-ENOMEM);

	dent_key_init(c, &key, dir->i_ino, &dentry->d_name);

	err = ubifs_tnc_lookup_nm(c, &key, dent, &dentry->d_name);
	if (err) {
		if (err == -ENOENT) {
			dbg_gen("not found");
			goto done;
		}
		goto out;
	}

	if (dbg_check_name(c, dent, &dentry->d_name)) {
		err = -EINVAL;
		goto out;
	}

	inode = ubifs_iget(dir->i_sb, le64_to_cpu(dent->inum));
	if (IS_ERR(inode)) {
		/*
		 * This should not happen. Probably the file-system needs
		 * checking.
		 */
		err = PTR_ERR(inode);
		ubifs_err("dead directory entry '%.*s', error %d",
			  dentry->d_name.len, dentry->d_name.name, err);
		ubifs_ro_mode(c, err);
		goto out;
	}

done:
	kfree(dent);
	/*
	 * Note, d_splice_alias() would be required instead if we supported
	 * NFS.
	 */
	d_add(dentry, inode);
	return NULL;

out:
	kfree(dent);
	return ERR_PTR(err);
}