Date:	Thu, 17 Apr 2008 09:51:53 +0200
From:	Jan Kara <jack@...e.cz>
To:	Bob Copeland <me@...copeland.com>
Cc:	linux-kernel@...r.kernel.org, vsu@...linux.ru
Subject: Re: [PATCH] udf: use crc_itu_t from lib instead of udf_crc

  Hello,

On Wed 16-04-08 21:07:11, Bob Copeland wrote:
> In reviewing a patch of mine, Sergey Vlasov noticed that the CRC used
> in UDF was recently added to lib/.  Would you accept a patch to switch
> UDF over?  Such as:
  Thanks for the patch. It is fine, only I had to do some merging because
of other cleanups clashing with your patch. Could you please generate the
diff against -mm kernel or UDF git
(git.kernel.org//pub/scm/linux/kernel/git/jack/linux-udf-2.6.git for_mm)
next time? It would be easier for me. Thanks.

								Honza

> From: Bob Copeland <me@...copeland.com>
> Date: Wed, 16 Apr 2008 20:23:31 -0400
> Subject: [PATCH] udf: use crc_itu_t from lib instead of udf_crc
> 
> As pointed out by Sergey Vlasov, UDF implements its own version of
> the CRC ITU-T V.41.  Convert it to use the one in the library.
> 
> Signed-off-by: Bob Copeland <me@...copeland.com>
> Cc: Sergey Vlasov <vsu@...linux.ru>
> ---
>  fs/Kconfig       |    1 +
>  fs/udf/Makefile  |    2 +-
>  fs/udf/crc.c     |  172 ------------------------------------------------------
>  fs/udf/inode.c   |   11 ++--
>  fs/udf/misc.c    |   12 ++--
>  fs/udf/namei.c   |   21 +++----
>  fs/udf/super.c   |   11 ++--
>  fs/udf/udfdecl.h |    3 -
>  fs/udf/unicode.c |    3 +-
>  9 files changed, 32 insertions(+), 204 deletions(-)
>  delete mode 100644 fs/udf/crc.c
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 5dd8f94..f18564f 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -663,6 +663,7 @@ config ZISOFS
>  
>  config UDF_FS
>  	tristate "UDF file system support"
> +	select CRC_ITU_T
>  	help
>  	  This is the new file system used on some CD-ROMs and DVDs. Say Y if
>  	  you intend to mount DVD discs or CDRW's written in packet mode, or
> diff --git a/fs/udf/Makefile b/fs/udf/Makefile
> index be845e7..0d4503f 100644
> --- a/fs/udf/Makefile
> +++ b/fs/udf/Makefile
> @@ -6,4 +6,4 @@ obj-$(CONFIG_UDF_FS) += udf.o
>  
>  udf-objs     := balloc.o dir.o file.o ialloc.o inode.o lowlevel.o namei.o \
>  		partition.o super.o truncate.o symlink.o fsync.o \
> -		crc.o directory.o misc.o udftime.o unicode.o
> +		directory.o misc.o udftime.o unicode.o
> diff --git a/fs/udf/crc.c b/fs/udf/crc.c
> deleted file mode 100644
> index b166129..0000000
> --- a/fs/udf/crc.c
> +++ /dev/null
> @@ -1,172 +0,0 @@
> -/*
> - * crc.c
> - *
> - * PURPOSE
> - *	Routines to generate, calculate, and test a 16-bit CRC.
> - *
> - * DESCRIPTION
> - *	The CRC code was devised by Don P. Mitchell of AT&T Bell Laboratories
> - *	and Ned W. Rhodes of Software Systems Group. It has been published in
> - *	"Design and Validation of Computer Protocols", Prentice Hall,
> - *	Englewood Cliffs, NJ, 1991, Chapter 3, ISBN 0-13-539925-4.
> - *
> - *	Copyright is held by AT&T.
> - *
> - *	AT&T gives permission for the free use of the CRC source code.
> - *
> - * 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.
> - */
> -
> -#include "udfdecl.h"
> -
> -static uint16_t crc_table[256] = {
> -	0x0000U, 0x1021U, 0x2042U, 0x3063U, 0x4084U, 0x50a5U, 0x60c6U, 0x70e7U,
> -	0x8108U, 0x9129U, 0xa14aU, 0xb16bU, 0xc18cU, 0xd1adU, 0xe1ceU, 0xf1efU,
> -	0x1231U, 0x0210U, 0x3273U, 0x2252U, 0x52b5U, 0x4294U, 0x72f7U, 0x62d6U,
> -	0x9339U, 0x8318U, 0xb37bU, 0xa35aU, 0xd3bdU, 0xc39cU, 0xf3ffU, 0xe3deU,
> -	0x2462U, 0x3443U, 0x0420U, 0x1401U, 0x64e6U, 0x74c7U, 0x44a4U, 0x5485U,
> -	0xa56aU, 0xb54bU, 0x8528U, 0x9509U, 0xe5eeU, 0xf5cfU, 0xc5acU, 0xd58dU,
> -	0x3653U, 0x2672U, 0x1611U, 0x0630U, 0x76d7U, 0x66f6U, 0x5695U, 0x46b4U,
> -	0xb75bU, 0xa77aU, 0x9719U, 0x8738U, 0xf7dfU, 0xe7feU, 0xd79dU, 0xc7bcU,
> -	0x48c4U, 0x58e5U, 0x6886U, 0x78a7U, 0x0840U, 0x1861U, 0x2802U, 0x3823U,
> -	0xc9ccU, 0xd9edU, 0xe98eU, 0xf9afU, 0x8948U, 0x9969U, 0xa90aU, 0xb92bU,
> -	0x5af5U, 0x4ad4U, 0x7ab7U, 0x6a96U, 0x1a71U, 0x0a50U, 0x3a33U, 0x2a12U,
> -	0xdbfdU, 0xcbdcU, 0xfbbfU, 0xeb9eU, 0x9b79U, 0x8b58U, 0xbb3bU, 0xab1aU,
> -	0x6ca6U, 0x7c87U, 0x4ce4U, 0x5cc5U, 0x2c22U, 0x3c03U, 0x0c60U, 0x1c41U,
> -	0xedaeU, 0xfd8fU, 0xcdecU, 0xddcdU, 0xad2aU, 0xbd0bU, 0x8d68U, 0x9d49U,
> -	0x7e97U, 0x6eb6U, 0x5ed5U, 0x4ef4U, 0x3e13U, 0x2e32U, 0x1e51U, 0x0e70U,
> -	0xff9fU, 0xefbeU, 0xdfddU, 0xcffcU, 0xbf1bU, 0xaf3aU, 0x9f59U, 0x8f78U,
> -	0x9188U, 0x81a9U, 0xb1caU, 0xa1ebU, 0xd10cU, 0xc12dU, 0xf14eU, 0xe16fU,
> -	0x1080U, 0x00a1U, 0x30c2U, 0x20e3U, 0x5004U, 0x4025U, 0x7046U, 0x6067U,
> -	0x83b9U, 0x9398U, 0xa3fbU, 0xb3daU, 0xc33dU, 0xd31cU, 0xe37fU, 0xf35eU,
> -	0x02b1U, 0x1290U, 0x22f3U, 0x32d2U, 0x4235U, 0x5214U, 0x6277U, 0x7256U,
> -	0xb5eaU, 0xa5cbU, 0x95a8U, 0x8589U, 0xf56eU, 0xe54fU, 0xd52cU, 0xc50dU,
> -	0x34e2U, 0x24c3U, 0x14a0U, 0x0481U, 0x7466U, 0x6447U, 0x5424U, 0x4405U,
> -	0xa7dbU, 0xb7faU, 0x8799U, 0x97b8U, 0xe75fU, 0xf77eU, 0xc71dU, 0xd73cU,
> -	0x26d3U, 0x36f2U, 0x0691U, 0x16b0U, 0x6657U, 0x7676U, 0x4615U, 0x5634U,
> -	0xd94cU, 0xc96dU, 0xf90eU, 0xe92fU, 0x99c8U, 0x89e9U, 0xb98aU, 0xa9abU,
> -	0x5844U, 0x4865U, 0x7806U, 0x6827U, 0x18c0U, 0x08e1U, 0x3882U, 0x28a3U,
> -	0xcb7dU, 0xdb5cU, 0xeb3fU, 0xfb1eU, 0x8bf9U, 0x9bd8U, 0xabbbU, 0xbb9aU,
> -	0x4a75U, 0x5a54U, 0x6a37U, 0x7a16U, 0x0af1U, 0x1ad0U, 0x2ab3U, 0x3a92U,
> -	0xfd2eU, 0xed0fU, 0xdd6cU, 0xcd4dU, 0xbdaaU, 0xad8bU, 0x9de8U, 0x8dc9U,
> -	0x7c26U, 0x6c07U, 0x5c64U, 0x4c45U, 0x3ca2U, 0x2c83U, 0x1ce0U, 0x0cc1U,
> -	0xef1fU, 0xff3eU, 0xcf5dU, 0xdf7cU, 0xaf9bU, 0xbfbaU, 0x8fd9U, 0x9ff8U,
> -	0x6e17U, 0x7e36U, 0x4e55U, 0x5e74U, 0x2e93U, 0x3eb2U, 0x0ed1U, 0x1ef0U
> -};
> -
> -/*
> - * udf_crc
> - *
> - * PURPOSE
> - *	Calculate a 16-bit CRC checksum using ITU-T V.41 polynomial.
> - *
> - * DESCRIPTION
> - *	The OSTA-UDF(tm) 1.50 standard states that using CRCs is mandatory.
> - *	The polynomial used is:	x^16 + x^12 + x^15 + 1
> - *
> - * PRE-CONDITIONS
> - *	data		Pointer to the data block.
> - *	size		Size of the data block.
> - *
> - * POST-CONDITIONS
> - *	<return>	CRC of the data block.
> - *
> - * HISTORY
> - *	July 21, 1997 - Andrew E. Mileski
> - *	Adapted from OSTA-UDF(tm) 1.50 standard.
> - */
> -uint16_t udf_crc(uint8_t *data, uint32_t size, uint16_t crc)
> -{
> -	while (size--)
> -		crc = crc_table[(crc >> 8 ^ *(data++)) & 0xffU] ^ (crc << 8);
> -
> -	return crc;
> -}
> -
> -/****************************************************************************/
> -#if defined(TEST)
> -
> -/*
> - * PURPOSE
> - *	Test udf_crc()
> - *
> - * HISTORY
> - *	July 21, 1997 - Andrew E. Mileski
> - *	Adapted from OSTA-UDF(tm) 1.50 standard.
> - */
> -
> -unsigned char bytes[] = { 0x70U, 0x6AU, 0x77U };
> -
> -int main(void)
> -{
> -	unsigned short x;
> -
> -	x = udf_crc(bytes, sizeof bytes);
> -	printf("udf_crc: calculated = %4.4x, correct = %4.4x\n", x, 0x3299U);
> -
> -	return 0;
> -}
> -
> -#endif /* defined(TEST) */
> -
> -/****************************************************************************/
> -#if defined(GENERATE)
> -
> -/*
> - * PURPOSE
> - *	Generate a table for fast 16-bit CRC calculations (any polynomial).
> - *
> - * DESCRIPTION
> - *	The ITU-T V.41 polynomial is 010041.
> - *
> - * HISTORY
> - *	July 21, 1997 - Andrew E. Mileski
> - *	Adapted from OSTA-UDF(tm) 1.50 standard.
> - */
> -
> -#include <stdio.h>
> -
> -int main(int argc, char **argv)
> -{
> -	unsigned long crc, poly;
> -	int n, i;
> -
> -	/* Get the polynomial */
> -	sscanf(argv[1], "%lo", &poly);
> -	if (poly & 0xffff0000U) {
> -		fprintf(stderr, "polynomial is too large\en");
> -		exit(1);
> -	}
> -
> -	printf("/* CRC 0%o */\n", poly);
> -
> -	/* Create a table */
> -	printf("static unsigned short crc_table[256] = {\n");
> -	for (n = 0; n < 256; n++) {
> -		if (n % 8 == 0)
> -			printf("\t");
> -		crc = n << 8;
> -		for (i = 0; i < 8; i++) {
> -			if (crc & 0x8000U)
> -				crc = (crc << 1) ^ poly;
> -			else
> -				crc <<= 1;
> -			crc &= 0xFFFFU;
> -		}
> -		if (n == 255)
> -			printf("0x%04xU ", crc);
> -		else
> -			printf("0x%04xU, ", crc);
> -		if (n % 8 == 7)
> -			printf("\n");
> -	}
> -	printf("};\n");
> -
> -	return 0;
> -}
> -
> -#endif /* defined(GENERATE) */
> diff --git a/fs/udf/inode.c b/fs/udf/inode.c
> index 24cfa55..97297e7 100644
> --- a/fs/udf/inode.c
> +++ b/fs/udf/inode.c
> @@ -37,6 +37,7 @@
>  #include <linux/buffer_head.h>
>  #include <linux/writeback.h>
>  #include <linux/slab.h>
> +#include <linux/crc-itu-t.h>
>  
>  #include "udf_i.h"
>  #include "udf_sb.h"
> @@ -1488,9 +1489,9 @@ static int udf_update_inode(struct inode *inode, int do_sync)
>  						iinfo->i_location.
>  							logicalBlockNum);
>  		use->descTag.descCRCLength = cpu_to_le16(crclen);
> -		use->descTag.descCRC = cpu_to_le16(udf_crc((char *)use +
> -							   sizeof(tag), crclen,
> -							   0));
> +		use->descTag.descCRC = cpu_to_le16(crc_itu_t(0, (char *)use +
> +							   sizeof(tag), 
> +							   crclen));
>  		use->descTag.tagChecksum = udf_tag_checksum(&use->descTag);
>  
>  		mark_buffer_dirty(bh);
> @@ -1660,8 +1661,8 @@ static int udf_update_inode(struct inode *inode, int do_sync)
>  	crclen += iinfo->i_lenEAttr + iinfo->i_lenAlloc -
>  								sizeof(tag);
>  	fe->descTag.descCRCLength = cpu_to_le16(crclen);
> -	fe->descTag.descCRC = cpu_to_le16(udf_crc((char *)fe + sizeof(tag),
> -						  crclen, 0));
> +	fe->descTag.descCRC = cpu_to_le16(crc_itu_t(0, (char *)fe + sizeof(tag),
> +						  crclen));
>  	fe->descTag.tagChecksum = udf_tag_checksum(&fe->descTag);
>  
>  	/* write the data blocks */
> diff --git a/fs/udf/misc.c b/fs/udf/misc.c
> index a1d6da0..532bdf0 100644
> --- a/fs/udf/misc.c
> +++ b/fs/udf/misc.c
> @@ -25,6 +25,7 @@
>  #include <linux/string.h>
>  #include <linux/udf_fs.h>
>  #include <linux/buffer_head.h>
> +#include <linux/crc-itu-t.h>
>  
>  #include "udf_i.h"
>  #include "udf_sb.h"
> @@ -136,8 +137,8 @@ struct genericFormat *udf_add_extendedattr(struct inode *inode, uint32_t size,
>  		/* rewrite CRC + checksum of eahd */
>  		crclen = sizeof(struct extendedAttrHeaderDesc) - sizeof(tag);
>  		eahd->descTag.descCRCLength = cpu_to_le16(crclen);
> -		eahd->descTag.descCRC = cpu_to_le16(udf_crc((char *)eahd +
> -						sizeof(tag), crclen, 0));
> +		eahd->descTag.descCRC = cpu_to_le16(crc_itu_t(0, (char *)eahd +
> +						sizeof(tag), crclen));
>  		eahd->descTag.tagChecksum = udf_tag_checksum(&eahd->descTag);
>  		iinfo->i_lenEAttr += size;
>  		return (struct genericFormat *)&ea[offset];
> @@ -244,8 +245,9 @@ struct buffer_head *udf_read_tagged(struct super_block *sb, uint32_t block,
>  
>  	/* Verify the descriptor CRC */
>  	if (le16_to_cpu(tag_p->descCRCLength) + sizeof(tag) > sb->s_blocksize ||
> -	    le16_to_cpu(tag_p->descCRC) == udf_crc(bh->b_data + sizeof(tag),
> -					le16_to_cpu(tag_p->descCRCLength), 0))
> +	    le16_to_cpu(tag_p->descCRC) == crc_itu_t(0, 
> +					bh->b_data + sizeof(tag),
> +					le16_to_cpu(tag_p->descCRCLength)))
>  		return bh;
>  
>  	udf_debug("Crc failure block %d: crc = %d, crclen = %d\n",
> @@ -270,7 +272,7 @@ void udf_update_tag(char *data, int length)
>  	length -= sizeof(tag);
>  
>  	tptr->descCRCLength = cpu_to_le16(length);
> -	tptr->descCRC = cpu_to_le16(udf_crc(data + sizeof(tag), length, 0));
> +	tptr->descCRC = cpu_to_le16(crc_itu_t(0, data + sizeof(tag), length));
>  	tptr->tagChecksum = udf_tag_checksum(tptr);
>  }
>  
> diff --git a/fs/udf/namei.c b/fs/udf/namei.c
> index 112a5fb..168d2e9 100644
> --- a/fs/udf/namei.c
> +++ b/fs/udf/namei.c
> @@ -31,6 +31,7 @@
>  #include <linux/smp_lock.h>
>  #include <linux/buffer_head.h>
>  #include <linux/sched.h>
> +#include <linux/crc-itu-t.h>
>  
>  static inline int udf_match(int len1, const char *name1, int len2,
>  			    const char *name2)
> @@ -97,25 +98,23 @@ int udf_write_fi(struct inode *inode, struct fileIdentDesc *cfi,
>  		memset(fibh->ebh->b_data, 0x00, padlen + offset);
>  	}
>  
> -	crc = udf_crc((uint8_t *)cfi + sizeof(tag),
> -		      sizeof(struct fileIdentDesc) - sizeof(tag), 0);
> +	crc = crc_itu_t(0, (uint8_t *)cfi + sizeof(tag),
> +		      sizeof(struct fileIdentDesc) - sizeof(tag));
>  
>  	if (fibh->sbh == fibh->ebh) {
> -		crc = udf_crc((uint8_t *)sfi->impUse,
> +		crc = crc_itu_t(crc, (uint8_t *)sfi->impUse,
>  			      crclen + sizeof(tag) -
> -			      sizeof(struct fileIdentDesc), crc);
> +			      sizeof(struct fileIdentDesc));
>  	} else if (sizeof(struct fileIdentDesc) >= -fibh->soffset) {
> -		crc = udf_crc(fibh->ebh->b_data +
> +		crc = crc_itu_t(crc, fibh->ebh->b_data +
>  					sizeof(struct fileIdentDesc) +
>  					fibh->soffset,
>  			      crclen + sizeof(tag) -
> -					sizeof(struct fileIdentDesc),
> -			      crc);
> +					sizeof(struct fileIdentDesc));
>  	} else {
> -		crc = udf_crc((uint8_t *)sfi->impUse,
> -			      -fibh->soffset - sizeof(struct fileIdentDesc),
> -			      crc);
> -		crc = udf_crc(fibh->ebh->b_data, fibh->eoffset, crc);
> +		crc = crc_itu_t(crc, (uint8_t *)sfi->impUse,
> +			      -fibh->soffset - sizeof(struct fileIdentDesc));
> +		crc = crc_itu_t(crc, fibh->ebh->b_data, fibh->eoffset);
>  	}
>  
>  	cfi->descTag.descCRC = cpu_to_le16(crc);
> diff --git a/fs/udf/super.c b/fs/udf/super.c
> index f3ac4ab..a8194c7 100644
> --- a/fs/udf/super.c
> +++ b/fs/udf/super.c
> @@ -55,6 +55,7 @@
>  #include <linux/errno.h>
>  #include <linux/mount.h>
>  #include <linux/seq_file.h>
> +#include <linux/crc-itu-t.h>
>  #include <asm/byteorder.h>
>  
>  #include <linux/udf_fs.h>
> @@ -1644,9 +1645,8 @@ static void udf_open_lvid(struct super_block *sb)
>  		lvid->integrityType = LVID_INTEGRITY_TYPE_OPEN;
>  
>  		lvid->descTag.descCRC = cpu_to_le16(
> -			udf_crc((char *)lvid + sizeof(tag),
> -				le16_to_cpu(lvid->descTag.descCRCLength),
> -				0));
> +			crc_itu_t(0, (char *)lvid + sizeof(tag),
> +				le16_to_cpu(lvid->descTag.descCRCLength)));
>  
>  		lvid->descTag.tagChecksum = udf_tag_checksum(&lvid->descTag);
>  		mark_buffer_dirty(bh);
> @@ -1682,9 +1682,8 @@ static void udf_close_lvid(struct super_block *sb)
>  		lvid->integrityType = cpu_to_le32(LVID_INTEGRITY_TYPE_CLOSE);
>  
>  		lvid->descTag.descCRC = cpu_to_le16(
> -			udf_crc((char *)lvid + sizeof(tag),
> -				le16_to_cpu(lvid->descTag.descCRCLength),
> -				0));
> +			crc_itu_t(0, (char *)lvid + sizeof(tag),
> +				le16_to_cpu(lvid->descTag.descCRCLength)));
>  
>  		lvid->descTag.tagChecksum = udf_tag_checksum(&lvid->descTag);
>  		mark_buffer_dirty(bh);
> diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
> index 681dc2b..82ac3aa 100644
> --- a/fs/udf/udfdecl.h
> +++ b/fs/udf/udfdecl.h
> @@ -191,9 +191,6 @@ extern struct fileIdentDesc *udf_get_fileident(void *buffer, int bufsize,
>  extern long_ad *udf_get_filelongad(uint8_t *, int, uint32_t *, int);
>  extern short_ad *udf_get_fileshortad(uint8_t *, int, uint32_t *, int);
>  
> -/* crc.c */
> -extern uint16_t udf_crc(uint8_t *, uint32_t, uint16_t);
> -
>  /* udftime.c */
>  extern time_t *udf_stamp_to_time(time_t *, long *, kernel_timestamp);
>  extern kernel_timestamp *udf_time_to_stamp(kernel_timestamp *, struct timespec);
> diff --git a/fs/udf/unicode.c b/fs/udf/unicode.c
> index e533b11..e951cca 100644
> --- a/fs/udf/unicode.c
> +++ b/fs/udf/unicode.c
> @@ -24,6 +24,7 @@
>  #include <linux/string.h>	/* for memset */
>  #include <linux/nls.h>
>  #include <linux/udf_fs.h>
> +#include <linux/crc-itu-t.h>
>  
>  #include "udf_sb.h"
>  
> @@ -463,7 +464,7 @@ static int udf_translate_to_linux(uint8_t *newName, uint8_t *udfName,
>  		} else if (newIndex > 250)
>  			newIndex = 250;
>  		newName[newIndex++] = CRC_MARK;
> -		valueCRC = udf_crc(fidName, fidNameLen, 0);
> +		valueCRC = crc_itu_t(0, fidName, fidNameLen);
>  		newName[newIndex++] = hexChar[(valueCRC & 0xf000) >> 12];
>  		newName[newIndex++] = hexChar[(valueCRC & 0x0f00) >> 8];
>  		newName[newIndex++] = hexChar[(valueCRC & 0x00f0) >> 4];
> -- 
> 1.5.4.2.182.gb3092
> 
> -- 
> Bob Copeland %% www.bobcopeland.com 
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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