[PATCH] NFS: add filehandle crc for debug display

[Weston Andros Adamson <dros@netapp.com>]

Match wireshark's CRC-32 hash for easier debugging

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
---
Reposted with Trond's suggestion of splitting out hash calculation to a 
separate function.  Now dprintks can use a fh's CRC instead of the 
multiline nfs_display_fhandle() when it makes sense.

 fs/nfs/inode.c         |   23 ++++++++++++++++++++---
 include/linux/nfs_fs.h |    8 ++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 99a4f52..3919ceb 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -39,6 +39,7 @@
 #include <linux/slab.h>
 #include <linux/compat.h>
 #include <linux/freezer.h>
+#include <linux/crc32.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -1045,7 +1046,23 @@ struct nfs_fh *nfs_alloc_fhandle(void)
 	return fh;
 }
 
-/**
+#ifdef RPC_DEBUG
+/*
+ * _nfs_display_fhandle_hash - calculate the crc32 hash for the filehandle
+ *                             in the same way that wireshark does
+ *
+ * @fh: file handle
+ *
+ * For debugging only.
+ */
+u32 _nfs_display_fhandle_hash(const struct nfs_fh *fh)
+{
+	/* wireshark uses 32-bit AUTODIN crc and does a bitwise
+	 * not on the result */
+	return ~crc32(0xFFFFFFFF, &fh->data[0], fh->size);
+}
+
+/*
  * _nfs_display_fhandle - display an NFS file handle on the console
  *
  * @fh: file handle to display
@@ -1053,7 +1070,6 @@ struct nfs_fh *nfs_alloc_fhandle(void)
  *
  * For debugging only.
  */
-#ifdef RPC_DEBUG
 void _nfs_display_fhandle(const struct nfs_fh *fh, const char *caption)
 {
 	unsigned short i;
@@ -1063,7 +1079,8 @@ void _nfs_display_fhandle(const struct nfs_fh *fh, const char *caption)
 		return;
 	}
 
-	printk(KERN_DEFAULT "%s at %p is %u bytes:\n", caption, fh, fh->size);
+	printk(KERN_DEFAULT "%s at %p is %u bytes, crc: 0x%08x:\n",
+	       caption, fh, fh->size, _nfs_display_fhandle_hash(fh));
 	for (i = 0; i < fh->size; i += 16) {
 		__be32 *pos = (__be32 *)&fh->data[i];
 
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index c07a757..ce8e436 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -396,6 +396,11 @@ static inline void nfs_free_fhandle(const struct nfs_fh *fh)
 }
 
 #ifdef RPC_DEBUG
+extern u32 _nfs_display_fhandle_hash(const struct nfs_fh *fh);
+static inline u32 nfs_display_fhandle_hash(const struct nfs_fh *fh)
+{
+	return _nfs_display_fhandle_hash(fh);
+}
 extern void _nfs_display_fhandle(const struct nfs_fh *fh, const char *caption);
 #define nfs_display_fhandle(fh, caption)			\
 	do {							\
@@ -403,6 +408,9 @@ extern void _nfs_display_fhandle(const struct nfs_fh *fh, const char *caption);
 			_nfs_display_fhandle(fh, caption);	\
 	} while (0)
 #else
+static inline u32 nfs_display_fhandle_hash(const struct nfs_fh *fh)
+{
+}
 static inline void nfs_display_fhandle(const struct nfs_fh *fh,
 				       const char *caption)
 {
-- 
1.7.4.4