linux-kernel - Re: [PATCH 6/7] omfs: add checksumming routines

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Date:	Thu, 27 Mar 2008 16:41:14 +0300
From:	Sergey Vlasov <vsu@...linux.ru>
To:	Bob Copeland <me@...copeland.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 6/7] omfs: add checksumming routines

On Wed, 26 Mar 2008 20:45:59 -0400 Bob Copeland wrote:

> OMFS checksums the metadata of all filesystem objects.  This change adds
> the necessary functions to do so.
>
> Signed-off-by: Bob Copeland <me@...copeland.com>
> ---
>  fs/omfs/checksum.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 48 insertions(+), 0 deletions(-)
>  create mode 100644 fs/omfs/checksum.c
>
> diff --git a/fs/omfs/checksum.c b/fs/omfs/checksum.c
> new file mode 100644
> index 0000000..d6f1023
> --- /dev/null
> +++ b/fs/omfs/checksum.c
> @@ -0,0 +1,48 @@
> +#include <linux/fs.h>
> +#include <linux/buffer_head.h>
> +#include "omfs.h"
> +
> +#define POLY 0x1021
> +
> +/*
> + * crc-ccitt with MSB first (i.e., backwards), so we can't use the
> + * kernel table as-is.
> + */
> +static u16 omfs_crc(u16 crc, unsigned char *buf, int count)
> +{
> +	int i, j;
> +	for (i = 0; i < count; i++) {
> +		crc ^= buf[i] << 8;
> +		for (j = 0; j < 8; j++)
> +			crc = (crc << 1) ^ ((crc & 0x8000) ? POLY : 0);
> +	}
> +	return crc;
> +}

Is this the same as crc_itu_t() from lib/crc-itu-t.c (also duplicated
in fs/udf/crc.c)?

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