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[PATCH 1/2] xfs: add CRC infrastructure

To: xfs@xxxxxxxxxxx
Subject: [PATCH 1/2] xfs: add CRC infrastructure
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 8 Nov 2012 00:37:31 +1100
In-reply-to: <1352295452-4726-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1352295452-4726-1-git-send-email-david@xxxxxxxxxxxxx>
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>
---
 fs/xfs/Kconfig     |    1 +
 fs/xfs/uuid.h      |    6 +++++
 fs/xfs/xfs_cksum.h |   62 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_linux.h |    1 +
 fs/xfs/xfs_sb.h    |   10 ++++++++-
 5 files changed, 79 insertions(+), 1 deletion(-)
 create mode 100644 fs/xfs/xfs_cksum.h

diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig
index 6100ec0..5a7ffe5 100644
--- a/fs/xfs/Kconfig
+++ b/fs/xfs/Kconfig
@@ -2,6 +2,7 @@ config XFS_FS
        tristate "XFS filesystem support"
        depends on BLOCK
        select EXPORTFS
+       select LIBCRC32C
        help
          XFS is a high performance journaling filesystem which originated
          on the SGI IRIX platform.  It is completely multi-threaded, can
diff --git a/fs/xfs/uuid.h b/fs/xfs/uuid.h
index 4732d71..104db0f 100644
--- a/fs/xfs/uuid.h
+++ b/fs/xfs/uuid.h
@@ -26,4 +26,10 @@ extern int uuid_is_nil(uuid_t *uuid);
 extern int uuid_equal(uuid_t *uuid1, uuid_t *uuid2);
 extern void uuid_getnodeuniq(uuid_t *uuid, int fsid [2]);
 
+static inline void
+uuid_copy(uuid_t *dst, uuid_t *src)
+{
+       memcpy(dst, src, sizeof(uuid_t));
+}
+
 #endif /* __XFS_SUPPORT_UUID_H__ */
diff --git a/fs/xfs/xfs_cksum.h b/fs/xfs/xfs_cksum.h
new file mode 100644
index 0000000..623dd7b
--- /dev/null
+++ b/fs/xfs/xfs_cksum.h
@@ -0,0 +1,62 @@
+#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.
+ *
+ * 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;
+}
+
+/*
+ * 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);
+
+       *(__be32 *)(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 *(__be32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
+}
+
+#endif /* _XFS_CKSUM_H */
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 828662f..6e288e4 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -44,6 +44,7 @@
 #include <linux/kernel.h>
 #include <linux/blkdev.h>
 #include <linux/slab.h>
+#include <linux/crc32c.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/file.h>
diff --git a/fs/xfs/xfs_sb.h b/fs/xfs/xfs_sb.h
index f429d9d..666e89c 100644
--- a/fs/xfs/xfs_sb.h
+++ b/fs/xfs/xfs_sb.h
@@ -81,11 +81,13 @@ struct xfs_mount;
 #define XFS_SB_VERSION2_ATTR2BIT       0x00000008      /* Inline attr rework */
 #define XFS_SB_VERSION2_PARENTBIT      0x00000010      /* parent pointers */
 #define XFS_SB_VERSION2_PROJID32BIT    0x00000080      /* 32 bit project id */
+#define XFS_SB_VERSION2_CRCBIT         0x00000100      /* metadata CRCs */
 
 #define        XFS_SB_VERSION2_OKREALFBITS     \
        (XFS_SB_VERSION2_LAZYSBCOUNTBIT | \
         XFS_SB_VERSION2_ATTR2BIT       | \
-        XFS_SB_VERSION2_PROJID32BIT)
+        XFS_SB_VERSION2_PROJID32BIT    | \
+        XFS_SB_VERSION2_CRCBIT)
 #define        XFS_SB_VERSION2_OKSASHFBITS     \
        (0)
 #define XFS_SB_VERSION2_OKREALBITS     \
@@ -503,6 +505,12 @@ static inline int xfs_sb_version_hasprojid32bit(xfs_sb_t 
*sbp)
                (sbp->sb_features2 & XFS_SB_VERSION2_PROJID32BIT);
 }
 
+static inline int xfs_sb_version_hascrc(xfs_sb_t *sbp)
+{
+       return (xfs_sb_version_hasmorebits(sbp) &&
+               (sbp->sb_features2 & XFS_SB_VERSION2_CRCBIT));
+}
+
 /*
  * end of superblock version macros
  */
-- 
1.7.10

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