On 11/07/12 07:37, Dave Chinner wrote:
From: Christoph Hellwig<hch@xxxxxx>
- 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 losely based on similar ones in sctp,
all other bits come from Dave Chinner.
Signed-off-by: Christoph Hellwig<hch@xxxxxx>
Signed-off-by: Dave Chinner<dchinner@xxxxxxxxxx>
---
+/*
+ * 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));
I know this came from sctp and I know I can't convince you to copy/null
the *cksum_offset to make one block for those with hardware crc32c devices.
Since the *cksum_offset value is never used in creating and verifying
the checksum, the 4 bytes of zeros does not add any new information,
why not just drop it from the cksum calculation?
+
+ /* 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.
+ *
+ * Note that crc32c is already endianess agnostic, so no additional
+ * byte swap is needed.
+ */
+static inline __be32
+xfs_end_cksum(__uint32_t crc)
+{
+ return (__force __be32)~crc;
+}
+
Wouldn't you have to cpu_to_le32() for big endian machines?
commit 9c5ff5f75d0d0a1c7928ecfae3f38418b51a88e3
Author: Vlad Yasevich <vladislav.yasevich@xxxxxx>
Date: Thu Jan 22 14:52:23 2009 -0800
sctp: Fix crc32c calculations on big-endian arhes.
crc32c algorithm provides a byteswaped result. On little-endian
arches, the result ends up in big-endian/network byte order.
On big-endinan arches, the result ends up in little-endian
order and needs to be byte swapped again. Thus calling cpu_to_le32
gives the right output.
Tested-by: Jukka Taimisto <jukka.taimisto@xxxxxxxxxxxxxx>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@xxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
diff --git a/include/net/sctp/checksum.h b/include/net/sctp/checksum.h
index b799fb2..2fec3c3 100644
--- a/include/net/sctp/checksum.h
+++ b/include/net/sctp/checksum.h
@@ -79,5 +79,5 @@ static inline __be32 sctp_update_cksum(__u8 *buffer,
__u16 length, __be32 crc32)
static inline __be32 sctp_end_cksum(__be32 crc32)
{
- return ~crc32;
+ return (__force __be32)~cpu_to_le32((__force u32)crc32);
}
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