dynamic_debug: describe_flags with '=[pmflt_]*'

Change describe_flags() to emit '=[pmflt_]+' for current callsite
flags, or just '=_' when they're disabled.  Having '=' in output
allows a more selective grep expression; in contrast '-' may appear
in filenames, line-ranges, and format-strings.  '=' also has better
mnemonics, saying; "the current setting is equal to <flags>".

This allows grep "=_" <dbgfs>/dynamic_debug/control to see disabled
callsites while avoiding the many occurrences of " = " seen in format
strings.

Enlarge flagsbufs to handle additional flag char, and alter
ddebug_parse_flags() to allow flags=0, so that user can turn off all
debug flags via:

  ~# echo =_ > <dbgfs>/dynamic_debug/control

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 12 insertions, 12 deletions

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 29ea09ae30cf..fc39640f2dea 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -21,7 +21,8 @@ struct _ddebug {
          * The bits here are changed dynamically when the user
          * writes commands to <debugfs>/dynamic_debug/control
          */
-#define _DPRINTK_FLAGS_PRINT   (1<<0)  /* printk() a message using the format */
+#define _DPRINTK_FLAGS_NONE     0
+#define _DPRINTK_FLAGS_PRINT    (1<<0) /* printk() a message using the format */
 #define _DPRINTK_FLAGS_INCL_MODNAME     (1<<1)
 #define _DPRINTK_FLAGS_INCL_FUNCNAME    (1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO      (1<<3)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index b199e0935053..cde4dfe2b2d5 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -75,6 +75,7 @@ static struct { unsigned flag:8; char opt_char; } opt_array[] = {
         { _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
         { _DPRINTK_FLAGS_INCL_LINENO, 'l' },
         { _DPRINTK_FLAGS_INCL_TID, 't' },
+        { _DPRINTK_FLAGS_NONE, '_' },
 };
 
 /* format a string into buf[] which describes the _ddebug's flags */
@@ -84,12 +85,12 @@ static char *ddebug_describe_flags(struct _ddebug *dp, char *buf,
         char *p = buf;
         int i;
 
-        BUG_ON(maxlen < 4);
+        BUG_ON(maxlen < 6);
         for (i = 0; i < ARRAY_SIZE(opt_array); ++i)
                 if (dp->flags & opt_array[i].flag)
                         *p++ = opt_array[i].opt_char;
         if (p == buf)
-                *p++ = '-';
+                *p++ = '_';
         *p = '\0';
 
         return buf;
@@ -108,7 +109,7 @@ static void ddebug_change(const struct ddebug_query *query,
         struct ddebug_table *dt;
         unsigned int newflags;
         unsigned int nfound = 0;
-        char flagbuf[8];
+        char flagbuf[10];
 
         /* search for matching ddebugs */
         mutex_lock(&ddebug_lock);
@@ -152,7 +153,7 @@ static void ddebug_change(const struct ddebug_query *query,
                                 continue;
                         dp->flags = newflags;
                         if (verbose)
-                                pr_info("changed %s:%d [%s]%s %s\n",
+                                pr_info("changed %s:%d [%s]%s =%s\n",
                                         dp->filename, dp->lineno,
                                         dt->mod_name, dp->function,
                                         ddebug_describe_flags(dp, flagbuf,
@@ -370,8 +371,6 @@ static int ddebug_parse_flags(const char *str, unsigned int *flagsp,
                 if (i < 0)
                         return -EINVAL;
         }
-        if (flags == 0)
-                return -EINVAL;
         if (verbose)
                 pr_info("flags=0x%x\n", flags);
 
@@ -666,7 +665,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
 {
         struct ddebug_iter *iter = m->private;
         struct _ddebug *dp = p;
-        char flagsbuf[8];
+        char flagsbuf[10];
 
         if (verbose)
                 pr_info("called m=%p p=%p\n", m, p);
@@ -677,10 +676,10 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
                 return 0;
         }
 
-        seq_printf(m, "%s:%u [%s]%s %s \"",
-                   dp->filename, dp->lineno,
-                   iter->table->mod_name, dp->function,
-                   ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
+        seq_printf(m, "%s:%u [%s]%s =%s \"",
+                dp->filename, dp->lineno,
+                iter->table->mod_name, dp->function,
+                ddebug_describe_flags(dp, flagsbuf, sizeof(flagsbuf)));
         seq_escape(m, dp->format, "\t\r\n\"");
         seq_puts(m, "\"\n");