From bc02e8693d875c2a9b0037cfd37fe0b726d26403 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Fri, 16 Nov 2012 09:20:37 +1100 Subject: xfs: add CRC infrastructure - add a mount feature bit for CRC enabled filesystems - add some helpers for generating and verifying the CRCs - add a copy_uuid helper The checksumming helpers are loosely based on similar ones in sctp, all other bits come from Dave Chinner. Signed-off-by: Christoph Hellwig Signed-off-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_cksum.h | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 fs/xfs/xfs_cksum.h (limited to 'fs/xfs/xfs_cksum.h') diff --git a/fs/xfs/xfs_cksum.h b/fs/xfs/xfs_cksum.h new file mode 100644 index 00000000000..fad1676ad8c --- /dev/null +++ b/fs/xfs/xfs_cksum.h @@ -0,0 +1,63 @@ +#ifndef _XFS_CKSUM_H +#define _XFS_CKSUM_H 1 + +#define XFS_CRC_SEED (~(__uint32_t)0) + +/* + * Calculate the intermediate checksum for a buffer that has the CRC field + * inside it. The offset of the 32bit crc fields is passed as the + * cksum_offset parameter. + */ +static inline __uint32_t +xfs_start_cksum(char *buffer, size_t length, unsigned long cksum_offset) +{ + __uint32_t zero = 0; + __uint32_t crc; + + /* Calculate CRC up to the checksum. */ + crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset); + + /* Skip checksum field */ + crc = crc32c(crc, &zero, sizeof(__u32)); + + /* Calculate the rest of the CRC. */ + return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)], + length - (cksum_offset + sizeof(__be32))); +} + +/* + * Convert the intermediate checksum to the final ondisk format. + * + * The CRC32c calculation uses LE format even on BE machines, but returns the + * result in host endian format. Hence we need to byte swap it back to LE format + * so that it is consistent on disk. + */ +static inline __le32 +xfs_end_cksum(__uint32_t crc) +{ + return ~cpu_to_le32(crc); +} + +/* + * Helper to generate the checksum for a buffer. + */ +static inline void +xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset) +{ + __uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset); + + *(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc); +} + +/* + * Helper to verify the checksum for a buffer. + */ +static inline int +xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset) +{ + __uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset); + + return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc); +} + +#endif /* _XFS_CKSUM_H */ -- cgit v1.2.3