[mirror_ubuntu-artful-kernel.git] / fs / udf / misc.c

/*
 * misc.c
 *
 * PURPOSE
 *	Miscellaneous routines for the OSTA-UDF(tm) filesystem.
 *
 * COPYRIGHT
 *	This file is distributed under the terms of the GNU General Public
 *	License (GPL). Copies of the GPL can be obtained from:
 *		ftp://prep.ai.mit.edu/pub/gnu/GPL
 *	Each contributing author retains all rights to their own work.
 *
 *  (C) 1998 Dave Boynton
 *  (C) 1998-2004 Ben Fennema
 *  (C) 1999-2000 Stelias Computing Inc
 *
 * HISTORY
 *
 *  04/19/99 blf  partial support for reading/writing specific EA's
 */

#include "udfdecl.h"

#include <linux/fs.h>
#include <linux/string.h>
#include <linux/crc-itu-t.h>

#include "udf_i.h"
#include "udf_sb.h"

struct buffer_head *udf_tgetblk(struct super_block *sb, int block)
{
	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
		return sb_getblk(sb, udf_fixed_to_variable(block));
	else
		return sb_getblk(sb, block);
}

struct buffer_head *udf_tread(struct super_block *sb, int block)
{
	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
		return sb_bread(sb, udf_fixed_to_variable(block));
	else
		return sb_bread(sb, block);
}

struct genericFormat *udf_add_extendedattr(struct inode *inode, uint32_t size,
					   uint32_t type, uint8_t loc)
{
	uint8_t *ea = NULL, *ad = NULL;
	int offset;
	uint16_t crclen;
	struct udf_inode_info *iinfo = UDF_I(inode);

	ea = iinfo->i_ext.i_data;
	if (iinfo->i_lenEAttr) {
		ad = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
	} else {
		ad = ea;
		size += sizeof(struct extendedAttrHeaderDesc);
	}

	offset = inode->i_sb->s_blocksize - udf_file_entry_alloc_offset(inode) -
		iinfo->i_lenAlloc;

	/* TODO - Check for FreeEASpace */

	if (loc & 0x01 && offset >= size) {
		struct extendedAttrHeaderDesc *eahd;
		eahd = (struct extendedAttrHeaderDesc *)ea;

		if (iinfo->i_lenAlloc)
			memmove(&ad[size], ad, iinfo->i_lenAlloc);

		if (iinfo->i_lenEAttr) {
			/* check checksum/crc */
			if (eahd->descTag.tagIdent !=
					cpu_to_le16(TAG_IDENT_EAHD) ||
			    le32_to_cpu(eahd->descTag.tagLocation) !=
					iinfo->i_location.logicalBlockNum)
				return NULL;
		} else {
			struct udf_sb_info *sbi = UDF_SB(inode->i_sb);

			size -= sizeof(struct extendedAttrHeaderDesc);
			iinfo->i_lenEAttr +=
				sizeof(struct extendedAttrHeaderDesc);
			eahd->descTag.tagIdent = cpu_to_le16(TAG_IDENT_EAHD);
			if (sbi->s_udfrev >= 0x0200)
				eahd->descTag.descVersion = cpu_to_le16(3);
			else
				eahd->descTag.descVersion = cpu_to_le16(2);
			eahd->descTag.tagSerialNum =
					cpu_to_le16(sbi->s_serial_number);
			eahd->descTag.tagLocation = cpu_to_le32(
					iinfo->i_location.logicalBlockNum);
			eahd->impAttrLocation = cpu_to_le32(0xFFFFFFFF);
			eahd->appAttrLocation = cpu_to_le32(0xFFFFFFFF);
		}

		offset = iinfo->i_lenEAttr;
		if (type < 2048) {
			if (le32_to_cpu(eahd->appAttrLocation) <
					iinfo->i_lenEAttr) {
				uint32_t aal =
					le32_to_cpu(eahd->appAttrLocation);

				osb();
				memmove(&ea[offset - aal + size],
					&ea[aal], offset - aal);
				offset -= aal;
				eahd->appAttrLocation =
						cpu_to_le32(aal + size);
			}
			if (le32_to_cpu(eahd->impAttrLocation) <
					iinfo->i_lenEAttr) {
				uint32_t ial =
					le32_to_cpu(eahd->impAttrLocation);

				osb();
				memmove(&ea[offset - ial + size],
					&ea[ial], offset - ial);
				offset -= ial;
				eahd->impAttrLocation =
						cpu_to_le32(ial + size);
			}
		} else if (type < 65536) {
			if (le32_to_cpu(eahd->appAttrLocation) <
					iinfo->i_lenEAttr) {
				uint32_t aal =
					le32_to_cpu(eahd->appAttrLocation);

				osb();
				memmove(&ea[offset - aal + size],
					&ea[aal], offset - aal);
				offset -= aal;
				eahd->appAttrLocation =
						cpu_to_le32(aal + size);
			}
		}
		/* rewrite CRC + checksum of eahd */
		crclen = sizeof(struct extendedAttrHeaderDesc) - sizeof(struct tag);
		eahd->descTag.descCRCLength = cpu_to_le16(crclen);
		eahd->descTag.descCRC = cpu_to_le16(crc_itu_t(0, (char *)eahd +
						sizeof(struct tag), crclen));
		eahd->descTag.tagChecksum = udf_tag_checksum(&eahd->descTag);
		iinfo->i_lenEAttr += size;
		return (struct genericFormat *)&ea[offset];
	}

	return NULL;
}

struct genericFormat *udf_get_extendedattr(struct inode *inode, uint32_t type,
					   uint8_t subtype)
{
	struct genericFormat *gaf;
	uint8_t *ea = NULL;
	uint32_t offset;
	struct udf_inode_info *iinfo = UDF_I(inode);

	ea = iinfo->i_ext.i_data;

	if (iinfo->i_lenEAttr) {
		struct extendedAttrHeaderDesc *eahd;
		eahd = (struct extendedAttrHeaderDesc *)ea;

		/* check checksum/crc */
		if (eahd->descTag.tagIdent !=
				cpu_to_le16(TAG_IDENT_EAHD) ||
		    le32_to_cpu(eahd->descTag.tagLocation) !=
				iinfo->i_location.logicalBlockNum)
			return NULL;

		if (type < 2048)
			offset = sizeof(struct extendedAttrHeaderDesc);
		else if (type < 65536)
			offset = le32_to_cpu(eahd->impAttrLocation);
		else
			offset = le32_to_cpu(eahd->appAttrLocation);

		while (offset < iinfo->i_lenEAttr) {
			gaf = (struct genericFormat *)&ea[offset];
			if (le32_to_cpu(gaf->attrType) == type &&
					gaf->attrSubtype == subtype)
				return gaf;
			else
				offset += le32_to_cpu(gaf->attrLength);
		}
	}

	return NULL;
}

/*
 * udf_read_tagged
 *
 * PURPOSE
 *	Read the first block of a tagged descriptor.
 *
 * HISTORY
 *	July 1, 1997 - Andrew E. Mileski
 *	Written, tested, and released.
 */
struct buffer_head *udf_read_tagged(struct super_block *sb, uint32_t block,
				    uint32_t location, uint16_t *ident)
{
	struct tag *tag_p;
	struct buffer_head *bh = NULL;
	u8 checksum;

	/* Read the block */
	if (block == 0xFFFFFFFF)
		return NULL;

	bh = udf_tread(sb, block);
	if (!bh) {
		udf_err(sb, "read failed, block=%u, location=%d\n",
			block, location);
		return NULL;
	}

	tag_p = (struct tag *)(bh->b_data);

	*ident = le16_to_cpu(tag_p->tagIdent);

	if (location != le32_to_cpu(tag_p->tagLocation)) {
		udf_debug("location mismatch block %u, tag %u != %u\n",
			  block, le32_to_cpu(tag_p->tagLocation), location);
		goto error_out;
	}

	/* Verify the tag checksum */
	checksum = udf_tag_checksum(tag_p);
	if (checksum != tag_p->tagChecksum) {
		udf_err(sb, "tag checksum failed, block %u: 0x%02x != 0x%02x\n",
			block, checksum, tag_p->tagChecksum);
		goto error_out;
	}

	/* Verify the tag version */
	if (tag_p->descVersion != cpu_to_le16(0x0002U) &&
	    tag_p->descVersion != cpu_to_le16(0x0003U)) {
		udf_err(sb, "tag version 0x%04x != 0x0002 || 0x0003, block %u\n",
			le16_to_cpu(tag_p->descVersion), block);
		goto error_out;
	}

	/* Verify the descriptor CRC */
	if (le16_to_cpu(tag_p->descCRCLength) + sizeof(struct tag) > sb->s_blocksize ||
	    le16_to_cpu(tag_p->descCRC) == crc_itu_t(0,
					bh->b_data + sizeof(struct tag),
					le16_to_cpu(tag_p->descCRCLength)))
		return bh;

	udf_debug("Crc failure block %d: crc = %d, crclen = %d\n", block,
		  le16_to_cpu(tag_p->descCRC),
		  le16_to_cpu(tag_p->descCRCLength));
error_out:
	brelse(bh);
	return NULL;
}

struct buffer_head *udf_read_ptagged(struct super_block *sb,
				     struct kernel_lb_addr *loc,
				     uint32_t offset, uint16_t *ident)
{
	return udf_read_tagged(sb, udf_get_lb_pblock(sb, loc, offset),
			       loc->logicalBlockNum + offset, ident);
}

void udf_update_tag(char *data, int length)
{
	struct tag *tptr = (struct tag *)data;
	length -= sizeof(struct tag);

	tptr->descCRCLength = cpu_to_le16(length);
	tptr->descCRC = cpu_to_le16(crc_itu_t(0, data + sizeof(struct tag), length));
	tptr->tagChecksum = udf_tag_checksum(tptr);
}

void udf_new_tag(char *data, uint16_t ident, uint16_t version, uint16_t snum,
		 uint32_t loc, int length)
{
	struct tag *tptr = (struct tag *)data;
	tptr->tagIdent = cpu_to_le16(ident);
	tptr->descVersion = cpu_to_le16(version);
	tptr->tagSerialNum = cpu_to_le16(snum);
	tptr->tagLocation = cpu_to_le32(loc);
	udf_update_tag(data, length);
}

u8 udf_tag_checksum(const struct tag *t)
{
	u8 *data = (u8 *)t;
	u8 checksum = 0;
	int i;
	for (i = 0; i < sizeof(struct tag); ++i)
		if (i != 4) /* position of checksum */
			checksum += data[i];
	return checksum;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* misc.c
	3	*
	4	* PURPOSE
	5	* Miscellaneous routines for the OSTA-UDF(tm) filesystem.
	6	*
1da177e4 LT	7	* COPYRIGHT
	8	* This file is distributed under the terms of the GNU General Public
	9	* License (GPL). Copies of the GPL can be obtained from:
	10	* ftp://prep.ai.mit.edu/pub/gnu/GPL
	11	* Each contributing author retains all rights to their own work.
	12	*
	13	* (C) 1998 Dave Boynton
	14	* (C) 1998-2004 Ben Fennema
	15	* (C) 1999-2000 Stelias Computing Inc
	16	*
	17	* HISTORY
	18	*
	19	* 04/19/99 blf partial support for reading/writing specific EA's
	20	*/
	21
	22	#include "udfdecl.h"
	23
	24	#include <linux/fs.h>
	25	#include <linux/string.h>
f845fced	26	#include <linux/crc-itu-t.h>
1da177e4 LT	27
	28	#include "udf_i.h"
	29	#include "udf_sb.h"
	30
cb00ea35	31	struct buffer_head udf_tgetblk(struct super_block sb, int block)
1da177e4 LT	32	{
	33	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
	34	return sb_getblk(sb, udf_fixed_to_variable(block));
	35	else
	36	return sb_getblk(sb, block);
	37	}
	38
cb00ea35	39	struct buffer_head udf_tread(struct super_block sb, int block)
1da177e4 LT	40	{
	41	if (UDF_QUERY_FLAG(sb, UDF_FLAG_VARCONV))
	42	return sb_bread(sb, udf_fixed_to_variable(block));
	43	else
	44	return sb_bread(sb, block);
	45	}
	46
cb00ea35 CG	47	struct genericFormat udf_add_extendedattr(struct inode inode, uint32_t size,
cb00ea35 CG	48	uint32_t type, uint8_t loc)
1da177e4 LT	49	{
	50	uint8_t ea = NULL, ad = NULL;
	51	int offset;
	52	uint16_t crclen;
48d6d8ff	53	struct udf_inode_info *iinfo = UDF_I(inode);
1da177e4	54
48d6d8ff MS	55	ea = iinfo->i_ext.i_data;
	56	if (iinfo->i_lenEAttr) {
	57	ad = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
28de7948	58	} else {
1da177e4 LT	59	ad = ea;
	60	size += sizeof(struct extendedAttrHeaderDesc);
	61	}
	62
	63	offset = inode->i_sb->s_blocksize - udf_file_entry_alloc_offset(inode) -
48d6d8ff	64	iinfo->i_lenAlloc;
1da177e4 LT	65
	66	/* TODO - Check for FreeEASpace */
	67
cb00ea35	68	if (loc & 0x01 && offset >= size) {
1da177e4 LT	69	struct extendedAttrHeaderDesc *eahd;
	70	eahd = (struct extendedAttrHeaderDesc *)ea;
	71
48d6d8ff MS	72	if (iinfo->i_lenAlloc)
48d6d8ff MS	73	memmove(&ad[size], ad, iinfo->i_lenAlloc);
1da177e4	74
48d6d8ff	75	if (iinfo->i_lenEAttr) {
1da177e4	76	/* check checksum/crc */
5e0f0017 MS	77	if (eahd->descTag.tagIdent !=
5e0f0017 MS	78	cpu_to_le16(TAG_IDENT_EAHD) \|\|
4b11111a	79	le32_to_cpu(eahd->descTag.tagLocation) !=
48d6d8ff	80	iinfo->i_location.logicalBlockNum)
1da177e4	81	return NULL;
cb00ea35	82	} else {
6c79e987 MS	83	struct udf_sb_info *sbi = UDF_SB(inode->i_sb);
6c79e987 MS	84
1da177e4	85	size -= sizeof(struct extendedAttrHeaderDesc);
48d6d8ff	86	iinfo->i_lenEAttr +=
4b11111a	87	sizeof(struct extendedAttrHeaderDesc);
1da177e4	88	eahd->descTag.tagIdent = cpu_to_le16(TAG_IDENT_EAHD);
6c79e987	89	if (sbi->s_udfrev >= 0x0200)
1da177e4 LT	90	eahd->descTag.descVersion = cpu_to_le16(3);
	91	else
	92	eahd->descTag.descVersion = cpu_to_le16(2);
4b11111a MS	93	eahd->descTag.tagSerialNum =
	94	cpu_to_le16(sbi->s_serial_number);
	95	eahd->descTag.tagLocation = cpu_to_le32(
48d6d8ff	96	iinfo->i_location.logicalBlockNum);
1da177e4 LT	97	eahd->impAttrLocation = cpu_to_le32(0xFFFFFFFF);
	98	eahd->appAttrLocation = cpu_to_le32(0xFFFFFFFF);
	99	}
	100
48d6d8ff	101	offset = iinfo->i_lenEAttr;
cb00ea35	102	if (type < 2048) {
4b11111a	103	if (le32_to_cpu(eahd->appAttrLocation) <
48d6d8ff	104	iinfo->i_lenEAttr) {
4b11111a MS	105	uint32_t aal =
4b11111a MS	106	le32_to_cpu(eahd->appAttrLocation);
ce8861e5 ER	107
ce8861e5 ER	108	osb();
28de7948 CG	109	memmove(&ea[offset - aal + size],
28de7948 CG	110	&ea[aal], offset - aal);
1da177e4	111	offset -= aal;
4b11111a MS	112	eahd->appAttrLocation =
4b11111a MS	113	cpu_to_le32(aal + size);
1da177e4	114	}
4b11111a	115	if (le32_to_cpu(eahd->impAttrLocation) <
48d6d8ff	116	iinfo->i_lenEAttr) {
4b11111a MS	117	uint32_t ial =
4b11111a MS	118	le32_to_cpu(eahd->impAttrLocation);
ce8861e5 ER	119
ce8861e5 ER	120	osb();
28de7948 CG	121	memmove(&ea[offset - ial + size],
28de7948 CG	122	&ea[ial], offset - ial);
1da177e4	123	offset -= ial;
4b11111a MS	124	eahd->impAttrLocation =
4b11111a MS	125	cpu_to_le32(ial + size);
1da177e4	126	}
cb00ea35	127	} else if (type < 65536) {
4b11111a	128	if (le32_to_cpu(eahd->appAttrLocation) <
48d6d8ff	129	iinfo->i_lenEAttr) {
4b11111a MS	130	uint32_t aal =
4b11111a MS	131	le32_to_cpu(eahd->appAttrLocation);
ce8861e5 ER	132
ce8861e5 ER	133	osb();
28de7948 CG	134	memmove(&ea[offset - aal + size],
28de7948 CG	135	&ea[aal], offset - aal);
1da177e4	136	offset -= aal;
4b11111a MS	137	eahd->appAttrLocation =
4b11111a MS	138	cpu_to_le32(aal + size);
1da177e4 LT	139	}
	140	}
	141	/* rewrite CRC + checksum of eahd */
5ca4e4be	142	crclen = sizeof(struct extendedAttrHeaderDesc) - sizeof(struct tag);
1da177e4	143	eahd->descTag.descCRCLength = cpu_to_le16(crclen);
f845fced	144	eahd->descTag.descCRC = cpu_to_le16(crc_itu_t(0, (char *)eahd +
5ca4e4be	145	sizeof(struct tag), crclen));
3f2587bb	146	eahd->descTag.tagChecksum = udf_tag_checksum(&eahd->descTag);
48d6d8ff	147	iinfo->i_lenEAttr += size;
1da177e4 LT	148	return (struct genericFormat *)&ea[offset];
1da177e4 LT	149	}
28de7948	150
1da177e4 LT	151	return NULL;
	152	}
	153
cb00ea35 CG	154	struct genericFormat udf_get_extendedattr(struct inode inode, uint32_t type,
cb00ea35 CG	155	uint8_t subtype)
1da177e4 LT	156	{
	157	struct genericFormat *gaf;
	158	uint8_t *ea = NULL;
	159	uint32_t offset;
48d6d8ff	160	struct udf_inode_info *iinfo = UDF_I(inode);
1da177e4	161
48d6d8ff	162	ea = iinfo->i_ext.i_data;
1da177e4	163
48d6d8ff	164	if (iinfo->i_lenEAttr) {
1da177e4 LT	165	struct extendedAttrHeaderDesc *eahd;
	166	eahd = (struct extendedAttrHeaderDesc *)ea;
	167
	168	/* check checksum/crc */
5e0f0017 MS	169	if (eahd->descTag.tagIdent !=
5e0f0017 MS	170	cpu_to_le16(TAG_IDENT_EAHD) \|\|
4b11111a	171	le32_to_cpu(eahd->descTag.tagLocation) !=
48d6d8ff	172	iinfo->i_location.logicalBlockNum)
1da177e4	173	return NULL;
cb00ea35	174
1da177e4 LT	175	if (type < 2048)
	176	offset = sizeof(struct extendedAttrHeaderDesc);
	177	else if (type < 65536)
	178	offset = le32_to_cpu(eahd->impAttrLocation);
	179	else
	180	offset = le32_to_cpu(eahd->appAttrLocation);
	181
48d6d8ff	182	while (offset < iinfo->i_lenEAttr) {
1da177e4	183	gaf = (struct genericFormat *)&ea[offset];
4b11111a MS	184	if (le32_to_cpu(gaf->attrType) == type &&
4b11111a MS	185	gaf->attrSubtype == subtype)
1da177e4 LT	186	return gaf;
	187	else
	188	offset += le32_to_cpu(gaf->attrLength);
	189	}
	190	}
28de7948	191
1da177e4 LT	192	return NULL;
	193	}
	194
	195	/*
	196	* udf_read_tagged
	197	*
	198	* PURPOSE
	199	* Read the first block of a tagged descriptor.
	200	*
	201	* HISTORY
	202	* July 1, 1997 - Andrew E. Mileski
	203	* Written, tested, and released.
	204	*/
cb00ea35	205	struct buffer_head udf_read_tagged(struct super_block sb, uint32_t block,
4b11111a	206	uint32_t location, uint16_t *ident)
1da177e4	207	{
5ca4e4be	208	struct tag *tag_p;
1da177e4	209	struct buffer_head *bh = NULL;
7e273e3b	210	u8 checksum;
1da177e4 LT	211
	212	/* Read the block */
	213	if (block == 0xFFFFFFFF)
	214	return NULL;
	215
f4bcbbd9	216	bh = udf_tread(sb, block);
cb00ea35	217	if (!bh) {
8076c363 JP	218	udf_err(sb, "read failed, block=%u, location=%d\n",
8076c363 JP	219	block, location);
1da177e4 LT	220	return NULL;
	221	}
	222
5ca4e4be	223	tag_p = (struct tag *)(bh->b_data);
1da177e4 LT	224
	225	*ident = le16_to_cpu(tag_p->tagIdent);
	226
cb00ea35	227	if (location != le32_to_cpu(tag_p->tagLocation)) {
1da177e4	228	udf_debug("location mismatch block %u, tag %u != %u\n",
f4bcbbd9	229	block, le32_to_cpu(tag_p->tagLocation), location);
1da177e4 LT	230	goto error_out;
1da177e4 LT	231	}
cb00ea35	232
1da177e4	233	/* Verify the tag checksum */
7e273e3b JP	234	checksum = udf_tag_checksum(tag_p);
7e273e3b JP	235	if (checksum != tag_p->tagChecksum) {
8076c363 JP	236	udf_err(sb, "tag checksum failed, block %u: 0x%02x != 0x%02x\n",
8076c363 JP	237	block, checksum, tag_p->tagChecksum);
1da177e4 LT	238	goto error_out;
	239	}
	240
	241	/* Verify the tag version */
5e0f0017 MS	242	if (tag_p->descVersion != cpu_to_le16(0x0002U) &&
5e0f0017 MS	243	tag_p->descVersion != cpu_to_le16(0x0003U)) {
8076c363 JP	244	udf_err(sb, "tag version 0x%04x != 0x0002 \|\| 0x0003, block %u\n",
8076c363 JP	245	le16_to_cpu(tag_p->descVersion), block);
1da177e4 LT	246	goto error_out;
	247	}
	248
	249	/* Verify the descriptor CRC */
5ca4e4be	250	if (le16_to_cpu(tag_p->descCRCLength) + sizeof(struct tag) > sb->s_blocksize \|\|
f845fced	251	le16_to_cpu(tag_p->descCRC) == crc_itu_t(0,
5ca4e4be	252	bh->b_data + sizeof(struct tag),
f845fced	253	le16_to_cpu(tag_p->descCRCLength)))
1da177e4	254	return bh;
4b11111a	255
f4bcbbd9	256	udf_debug("Crc failure block %d: crc = %d, crclen = %d\n", block,
8076c363 JP	257	le16_to_cpu(tag_p->descCRC),
8076c363 JP	258	le16_to_cpu(tag_p->descCRCLength));
28de7948	259	error_out:
1da177e4 LT	260	brelse(bh);
	261	return NULL;
	262	}
	263
97e961fd PE	264	struct buffer_head udf_read_ptagged(struct super_block sb,
97e961fd PE	265	struct kernel_lb_addr *loc,
4b11111a	266	uint32_t offset, uint16_t *ident)
1da177e4 LT	267	{
1da177e4 LT	268	return udf_read_tagged(sb, udf_get_lb_pblock(sb, loc, offset),
97e961fd	269	loc->logicalBlockNum + offset, ident);
1da177e4 LT	270	}
1da177e4 LT	271
1da177e4 LT	272	void udf_update_tag(char *data, int length)
1da177e4 LT	273	{
5ca4e4be PE	274	struct tag tptr = (struct tag )data;
5ca4e4be PE	275	length -= sizeof(struct tag);
1da177e4	276
1da177e4	277	tptr->descCRCLength = cpu_to_le16(length);
5ca4e4be	278	tptr->descCRC = cpu_to_le16(crc_itu_t(0, data + sizeof(struct tag), length));
3f2587bb	279	tptr->tagChecksum = udf_tag_checksum(tptr);
1da177e4 LT	280	}
	281
	282	void udf_new_tag(char *data, uint16_t ident, uint16_t version, uint16_t snum,
cb00ea35	283	uint32_t loc, int length)
1da177e4	284	{
5ca4e4be	285	struct tag tptr = (struct tag )data;
1da177e4 LT	286	tptr->tagIdent = cpu_to_le16(ident);
	287	tptr->descVersion = cpu_to_le16(version);
	288	tptr->tagSerialNum = cpu_to_le16(snum);
	289	tptr->tagLocation = cpu_to_le32(loc);
	290	udf_update_tag(data, length);
	291	}
3f2587bb	292
5ca4e4be	293	u8 udf_tag_checksum(const struct tag *t)
3f2587bb MS	294	{
	295	u8 data = (u8 )t;
	296	u8 checksum = 0;
	297	int i;
5ca4e4be	298	for (i = 0; i < sizeof(struct tag); ++i)
3f2587bb MS	299	if (i != 4) /* position of checksum */
	300	checksum += data[i];
	301	return checksum;
	302	}