mirror of
https://github.com/torvalds/linux
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bc02e8693d
- 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 <hch@lst.de> Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Mark Tinguely <tinguely@sgi.com> Signed-off-by: Ben Myers <bpm@sgi.com>
63 lines
1.6 KiB
C
63 lines
1.6 KiB
C
#ifndef _XFS_CKSUM_H
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#define _XFS_CKSUM_H 1
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#define XFS_CRC_SEED (~(__uint32_t)0)
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/*
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* Calculate the intermediate checksum for a buffer that has the CRC field
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* inside it. The offset of the 32bit crc fields is passed as the
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* cksum_offset parameter.
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*/
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static inline __uint32_t
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xfs_start_cksum(char *buffer, size_t length, unsigned long cksum_offset)
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{
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__uint32_t zero = 0;
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__uint32_t crc;
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/* Calculate CRC up to the checksum. */
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crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset);
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/* Skip checksum field */
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crc = crc32c(crc, &zero, sizeof(__u32));
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/* Calculate the rest of the CRC. */
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return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)],
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length - (cksum_offset + sizeof(__be32)));
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}
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/*
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* Convert the intermediate checksum to the final ondisk format.
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*
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* The CRC32c calculation uses LE format even on BE machines, but returns the
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* result in host endian format. Hence we need to byte swap it back to LE format
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* so that it is consistent on disk.
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*/
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static inline __le32
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xfs_end_cksum(__uint32_t crc)
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{
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return ~cpu_to_le32(crc);
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}
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/*
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* Helper to generate the checksum for a buffer.
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*/
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static inline void
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xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
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{
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__uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
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*(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
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}
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/*
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* Helper to verify the checksum for a buffer.
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*/
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static inline int
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xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)
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{
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__uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
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return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
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}
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#endif /* _XFS_CKSUM_H */
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