SUNRPC/NFS: Add Kbuild dependencies for NFS_DEBUG/RPC_DEBUG

This allows us to turn on/off the dprintk() debugging interfaces for
those distributions that don't ship the 'rpcdebug' utility.
It also allows us to add Kbuild dependencies. Specifically, we already
know that dprintk() in general relies on CONFIG_SYSCTL. Now it turns out
that the NFS dprintks depend on CONFIG_CRC32 after we added support
for the filehandle hash.

Reported-by: Paul Gortmaker <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/Kconfig

···
 	depends on NFS_V4 && !NFS_USE_LEGACY_DNS
 	select DNS_RESOLVER
 	default y
+
+config NFS_DEBUG
+	bool
+	depends on NFS_FS && SUNRPC_DEBUG
+	select CRC32
+	default y

fs/nfs/inode.c

···
 	return fh;
 }
 
-#ifdef RPC_DEBUG
+#ifdef NFS_DEBUG
 /*
  * _nfs_display_fhandle_hash - calculate the crc32 hash for the filehandle
  *                             in the same way that wireshark does

fs/nfs/mount_clnt.c

···
 #include <linux/nfs_fs.h>
 #include "internal.h"
 
-#ifdef RPC_DEBUG
+#ifdef NFS_DEBUG
 # define NFSDBG_FACILITY	NFSDBG_MOUNT
 #endif
 

fs/nfs/nfsroot.c

···
 /* server:export path string passed to super.c */
 static char nfs_root_device[NFS_MAXPATHLEN + 1] __initdata = "";
 
-#ifdef RPC_DEBUG
+#ifdef NFS_DEBUG
 /*
  * When the "nfsrootdebug" kernel command line option is specified,
  * enable debugging messages for NFSROOT.

include/linux/nfs_fs.h

···
 
 #ifdef __KERNEL__
 
+/*
+ * Enable dprintk() debugging support for nfs client.
+ */
+#ifdef CONFIG_NFS_DEBUG
+# define NFS_DEBUG
+#endif
+
 #include <linux/in.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
···
 	kfree(fh);
 }
 
-#ifdef RPC_DEBUG
+#ifdef NFS_DEBUG
 extern u32 _nfs_display_fhandle_hash(const struct nfs_fh *fh);
 static inline u32 nfs_display_fhandle_hash(const struct nfs_fh *fh)
 {
···
 #define NFSDBG_ALL		0xFFFF
 
 #ifdef __KERNEL__
-
-/*
- * Enable debugging support for nfs client.
- * Requires RPC_DEBUG.
- */
-#ifdef RPC_DEBUG
-# define NFS_DEBUG
-#endif
 
 # undef ifdebug
 # ifdef NFS_DEBUG

include/linux/sunrpc/debug.h

···
 /*
  * Enable RPC debugging/profiling.
  */
-#ifdef CONFIG_SYSCTL
+#ifdef CONFIG_SUNRPC_DEBUG
 #define  RPC_DEBUG
 #endif
 #ifdef CONFIG_TRACEPOINTS

net/sunrpc/Kconfig

···
 	  Kerberos support should be installed.
 
 	  If unsure, say Y.
+
+config SUNRPC_DEBUG
+	bool "RPC: Enable dprintk debugging"
+	depends on SUNRPC && SYSCTL
+	help
+	  This option enables a sysctl-based debugging interface
+	  that is be used by the 'rpcdebug' utility to turn on or off
+	  logging of different aspects of the kernel RPC activity.
+
+	  Disabling this option will make your kernel slightly smaller,
+	  but makes troubleshooting NFS issues significantly harder.
+
+	  If unsure, say Y.