Dynamic debug: allow simple quoting of words

Allow simple quoting of words in the dynamic debug control language.

This allows more natural specification when using the control language
to match against printk formats, e.g

#echo -n 'format "Setting node for non-present cpu" +p' >
	/mnt/debugfs/dynamic_debug/control

instead of

#echo -n 'format Setting\040node\040for\040non-present\040cpu +p' >
	/mnt/debugfs/dynamic_debug/control

Adjust the dynamic debug documention to describe that and provide a
new example.  Adjust the existing examples in the documentation to
reflect the current whitespace escaping behaviour when reading the
control file.  Fix some minor documentation trailing whitespace.

Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Author: Greg Banks

Documentation/dynamic-debug-howto.txt

@@ -49,10 +49,10 @@ via:
 
 nullarbor:~ # cat <debugfs>/dynamic_debug/control
 # filename:lineno [module]function flags format
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:323 [svcxprt_rdma]svc_rdma_cleanup - "SVCRDMA\040Module\040Removed,\040deregister\040RPC\040RDMA\040transport\012"
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:341 [svcxprt_rdma]svc_rdma_init - "\011max_inline\040\040\040\040\040\040\040:\040%d\012"
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:340 [svcxprt_rdma]svc_rdma_init - "\011sq_depth\040\040\040\040\040\040\040\040\040:\040%d\012"
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:338 [svcxprt_rdma]svc_rdma_init - "\011max_requests\040\040\040\040\040:\040%d\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:323 [svcxprt_rdma]svc_rdma_cleanup - "SVCRDMA Module Removed, deregister RPC RDMA transport\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:341 [svcxprt_rdma]svc_rdma_init - "\011max_inline       : %d\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:340 [svcxprt_rdma]svc_rdma_init - "\011sq_depth         : %d\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svc_rdma.c:338 [svcxprt_rdma]svc_rdma_init - "\011max_requests     : %d\012"
 ...
 
 
@@ -72,7 +72,7 @@ you can view all the debug statement callsites with any non-default flags:
 
 nullarbor:~ # awk '$3 != "-"' <debugfs>/dynamic_debug/control
 # filename:lineno [module]function flags format
-/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c:1603 [sunrpc]svc_send p "svc_process:\040st_sendto\040returned\040%d\012"
+/usr/src/packages/BUILD/sgi-enhancednfs-1.4/default/net/sunrpc/svcsock.c:1603 [sunrpc]svc_send p "svc_process: st_sendto returned %d\012"
 
 
 Command Language Reference
@@ -166,11 +166,15 @@ format
     entire format, only some part.  Whitespace and other
     special characters can be escaped using C octal character
     escape \ooo notation, e.g. the space character is \040.
+    Alternatively, the string can be enclosed in double quote
+    characters (") or single quote characters (').
     Examples:
 
     format svcrdma:	    // many of the NFS/RDMA server dprintks
     format readahead	    // some dprintks in the readahead cache
-    format nfsd:\040SETATTR // how to match a format with whitespace
+    format nfsd:\040SETATTR // one way to match a format with whitespace
+    format "nfsd: SETATTR"  // a neater way to match a format with whitespace
+    format 'nfsd: SETATTR'  // yet another way to match a format with whitespace
 
 line
     The given line number or range of line numbers is compared
@@ -230,3 +234,7 @@ nullarbor:~ # echo -n 'func svc_process +p' >
 // disable all 12 messages in the function svc_process()
 nullarbor:~ # echo -n 'func svc_process -p' >
 				<debugfs>/dynamic_debug/control
+
+// enable messages for NFS calls READ, READLINK, READDIR and READDIR+.
+nullarbor:~ # echo -n 'format "nfsd: READ" +p' >
+				<debugfs>/dynamic_debug/control

lib/dynamic_debug.c

@@ -195,33 +195,46 @@ static void ddebug_change(const struct ddebug_query *query,
 		printk(KERN_INFO "ddebug: no matches for query\n");
 }
 
-/*
- * Wrapper around strsep() to collapse the multiple empty tokens
- * that it returns when fed sequences of separator characters.
- * Now, if we had strtok_r()...
- */
-static inline char *nearly_strtok_r(char **p, const char *sep)
-{
-	char *r;
-
-	while ((r = strsep(p, sep)) != NULL && *r == '\0')
-		;
-	return r;
-}
-
 /*
  * Split the buffer `buf' into space-separated words.
- * Return the number of such words or <0 on error.
+ * Handles simple " and ' quoting, i.e. without nested,
+ * embedded or escaped \".  Return the number of words
+ * or <0 on error.
  */
 static int ddebug_tokenize(char *buf, char *words[], int maxwords)
 {
 	int nwords = 0;
 
-	while (nwords < maxwords &&
-	       (words[nwords] = nearly_strtok_r(&buf, " \t\r\n")) != NULL)
-		nwords++;
-	if (buf)
-		return -EINVAL;	/* ran out of words[] before bytes */
+	while (*buf) {
+		char *end;
+
+		/* Skip leading whitespace */
+		while (*buf && isspace(*buf))
+			buf++;
+		if (!*buf)
+			break;	/* oh, it was trailing whitespace */
+
+		/* Run `end' over a word, either whitespace separated or quoted */
+		if (*buf == '"' || *buf == '\'') {
+			int quote = *buf++;
+			for (end = buf ; *end && *end != quote ; end++)
+				;
+			if (!*end)
+				return -EINVAL;	/* unclosed quote */
+		} else {
+			for (end = buf ; *end && !isspace(*end) ; end++)
+				;
+			BUG_ON(end == buf);
+		}
+		/* Here `buf' is the start of the word, `end' is one past the end */
+
+		if (nwords == maxwords)
+			return -EINVAL;	/* ran out of words[] before bytes */
+		if (*end)
+			*end++ = '\0';	/* terminate the word */
+		words[nwords++] = buf;
+		buf = end;
+	}
 
 	if (verbose) {
 		int i;