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SubjectRe: [PATCH 6/7] omfs: add checksumming routines
Version 2 of this patch, with changes:
- use lib/crc-itu-t.c instead of open-coded version

From 6ce3bb9ce2faaf937df0ec8e64c39e1adc403b2e Mon Sep 17 00:00:00 2001
From: Bob Copeland <me@bobcopeland.com>
Date: Thu, 27 Mar 2008 17:23:12 -0400
Subject: [PATCH] omfs: add checksumming routines

OMFS checksums the metadata of all filesystem objects. This change adds
the necessary functions to do so.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
---
fs/omfs/checksum.c | 31 +++++++++++++++++++++++++++++++
1 files changed, 31 insertions(+), 0 deletions(-)
create mode 100644 fs/omfs/checksum.c

diff --git a/fs/omfs/checksum.c b/fs/omfs/checksum.c
new file mode 100644
index 0000000..cbd0471
--- /dev/null
+++ b/fs/omfs/checksum.c
@@ -0,0 +1,31 @@
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/crc-itu-t.h>
+#include "omfs.h"
+
+/*
+ * Update the header checksums for a dirty inode based on its contents.
+ * Caller is expected to hold the buffer head underlying oi and mark it
+ * dirty.
+ */
+int omfs_update_checksums(struct omfs_inode *oi)
+{
+ int ret = 0;
+ int xor, i, ofs = 0, count;
+ u16 crc = 0;
+ unsigned char *ptr = (unsigned char *) oi;
+
+ count = be32_to_cpu(oi->i_head.h_body_size);
+ ofs = sizeof(struct omfs_header);
+
+ crc = crc_itu_t(crc, ptr + ofs, count);
+ oi->i_head.h_crc = cpu_to_be16(crc);
+
+ xor = ptr[0];
+ for (i = 1; i < OMFS_XOR_COUNT; i++)
+ xor ^= ptr[i];
+
+ oi->i_head.h_check_xor = xor;
+
+ return ret;
+}
--
1.5.4.2.182.gb3092

--
Bob Copeland %% www.bobcopeland.com



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