/*
* 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.
+ * cksum_offset parameter. We do not modify the buffer during verification,
+ * hence we have to split the CRC calculation across the cksum_offset.
*/
static inline __uint32_t
-xfs_start_cksum(char *buffer, size_t length, unsigned long cksum_offset)
+xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)
{
__uint32_t zero = 0;
__uint32_t crc;
length - (cksum_offset + sizeof(__be32)));
}
+/*
+ * Fast CRC method where the buffer is modified. Callers must have exclusive
+ * access to the buffer while the calculation takes place.
+ */
+static inline __uint32_t
+xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)
+{
+ /* zero the CRC field */
+ *(__le32 *)(buffer + cksum_offset) = 0;
+
+ /* single pass CRC calculation for the entire buffer */
+ return crc32c(XFS_CRC_SEED, buffer, length);
+}
+
/*
* Convert the intermediate checksum to the final ondisk format.
*
/*
* Helper to generate the checksum for a buffer.
+ *
+ * This modifies the buffer temporarily - callers must have exclusive
+ * access to the buffer while the calculation takes place.
*/
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);
+ __uint32_t crc = xfs_start_cksum_update(buffer, length, cksum_offset);
*(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
}
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);
+ __uint32_t crc = xfs_start_cksum_safe(buffer, length, cksum_offset);
return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
}