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authorPatrick McHardy <kaber@trash.net>2013-03-31 18:10:34 +0200
committerPatrick McHardy <kaber@trash.net>2013-03-31 18:10:34 +0200
commit70711d223510ba1773cfe1d7770a56141c815ff8 (patch)
tree4a71f38a3a554ddecaa31b7d8c6bc49b7d1705b4 /fs/xfs/xfs_cksum.h
parentd53b4ed072d9779cdf53582c46436dec06d0961f (diff)
parent19f949f52599ba7c3f67a5897ac6be14bfcb1200 (diff)
Merge tag 'v3.8' of /home/kaber/src/repos/linux
Linux 3.8 Signed-off-by: Patrick McHardy <kaber@trash.net> Conflicts: include/linux/Kbuild include/linux/netlink.h
Diffstat (limited to 'fs/xfs/xfs_cksum.h')
-rw-r--r--fs/xfs/xfs_cksum.h63
1 files changed, 63 insertions, 0 deletions
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 */