[PATCH] libkmod-module: add support for a patient module removal option

@@ -102,5 +102,6 @@ kmod_module_get_initstate
 kmod_module_initstate_str
 kmod_module_get_size
 kmod_module_get_refcnt
+kmod_module_get_refcnt_wait
 kmod_module_get_holders
 </SECTION>

@@ -1915,6 +1915,56 @@ KMOD_EXPORT int kmod_module_get_refcnt(const struct kmod_module *mod)
 	return (int)refcnt;
 }
 
+/**
+ * kmod_module_get_refcnt_wait:
+ * @mod: kmod module
+ * @wait: if true will wait until the refcnt is 0 patiently forever
+ *
+ * Get the ref count of this @mod, as returned by Linux Kernel, by reading
+ * /sys filesystem and wait patiently until the refcnt is 0, if the wait bool
+ * argument is set to true, otherwise this behaves just as the call
+ * kmod_module_get_refcnt(). Enabling wait is useful if you know for sure that
+ * the module is quiescing soon, and so you should be able to remove it soon.
+ * If wait is enabled, we wait 1 second per iteration check on the refcnt.
+ *
+ * Returns: the reference count on success or < 0 on failure.
+ */
+KMOD_EXPORT int kmod_module_get_refcnt_wait(const struct kmod_module *mod, bool wait)
+{
+	char path[PATH_MAX];
+	long refcnt;
+	int fd, err;
+
+	if (mod == NULL)
+		return -ENOENT;
+
+	snprintf(path, sizeof(path), "/sys/module/%s/refcnt", mod->name);
+
+	while (true) {
+		fd = open(path, O_RDONLY|O_CLOEXEC);
+		if (fd < 0) {
+			err = -errno;
+			DBG(mod->ctx, "could not open '%s': %s\n",
+				path, strerror(errno));
+			return err;
+		}
+
+		err = read_str_long(fd, &refcnt, 10);
+		close(fd);
+		if (err < 0) {
+			ERR(mod->ctx, "could not read integer from '%s': '%s'\n",
+				path, strerror(-err));
+			return err;
+		}
+		if ((refcnt <= 0) || (refcnt > 0 && !wait))
+			break;
+		ERR(mod->ctx, "%s refcnt is %ld waiting for it to become 0\n", mod->name, refcnt);
+		sleep(1);
+	}
+
+	return (int)refcnt;
+}
+
 /**
  * kmod_module_get_holders:
  * @mod: kmod module

@@ -217,6 +217,7 @@ enum kmod_module_initstate {
 const char *kmod_module_initstate_str(enum kmod_module_initstate state);
 int kmod_module_get_initstate(const struct kmod_module *mod);
 int kmod_module_get_refcnt(const struct kmod_module *mod);
+int kmod_module_get_refcnt_wait(const struct kmod_module *mod, bool wait);
 struct kmod_list *kmod_module_get_holders(const struct kmod_module *mod);
 struct kmod_list *kmod_module_get_sections(const struct kmod_module *mod);
 const char *kmod_module_section_get_name(const struct kmod_list *entry);

@@ -49,6 +49,7 @@ global:
 	kmod_module_initstate_str;
 	kmod_module_get_initstate;
 	kmod_module_get_refcnt;
+	kmod_module_get_refcnt_wait;
 	kmod_module_get_sections;
 	kmod_module_section_free_list;
 	kmod_module_section_get_name;

@@ -99,6 +99,7 @@ cdef extern from 'libkmod/libkmod.h':
     # Information regarding "live information" from module's state, as
     # returned by kernel
     int kmod_module_get_refcnt(const_kmod_module_ptr mod)
+    int kmod_module_get_refcnt_wait(const_kmod_module_ptr mod, bool install)
     long kmod_module_get_size(const_kmod_module_ptr mod)
 
     # Information retrieved from ELF headers and section

@@ -72,6 +72,10 @@ cdef class Module (object):
         return _libkmod_h.kmod_module_get_refcnt(self.module)
     refcnt = property(fget=_refcnt_get)
 
+    def _refcnt_get_wait(self, wait=False):
+        return _libkmod_h.kmod_module_get_refcnt_wait(self.module, wait)
+    refcnt = property(fget=_refcnt_get_wait)
+
     def _size_get(self):
         return _libkmod_h.kmod_module_get_size(self.module)
     size = property(fget=_size_get)

@@ -388,6 +388,28 @@
           </para>
         </listitem>
       </varlistentry>
+      <varlistentry>
+        <term>
+          <option>-p</option>
+        </term>
+        <term>
+          <option>--remove-patiently</option>
+        </term>
+        <listitem>
+          <para>
+            This option causes <command>modprobe</command> to try to patiently
+            remove a module by waiting until its refcnt is 0. It checks the refcnt
+            and if its 0 it will immediately remove the module. If the refcnt is
+            not 0, it will sleep 1 second and check the refcnt again, and repeat
+            this until an error is found or the refcnt is 0. You can send a signal
+            to this command if you do not want to wait anymore.
+          </para>
+          <para>
+            Removing modules may be done by test infrastruture code, it can also
+            be done to remove a live kernel patch.
+          </para>
+        </listitem>
+      </varlistentry>
       <varlistentry>
         <term>
           <option>-S</option>

@@ -39,6 +39,7 @@
     <cmdsynopsis>
       <command>rmmod</command>
       <arg><option>-f</option></arg>
+      <arg><option>-p</option></arg>
       <arg><option>-s</option></arg>
       <arg><option>-v</option></arg>
       <arg><replaceable>modulename</replaceable></arg>

@@ -92,6 +93,28 @@
           </para>
         </listitem>
       </varlistentry>
+      <varlistentry>
+        <term>
+          <option>-p</option>
+        </term>
+        <term>
+          <option>--remove-patiently</option>
+        </term>
+        <listitem>
+          <para>
+            This option tries to remove the module patiently by waiting
+            until the module refcnt is 0. It checks the refcnt
+            and if its 0 it will immediately remove the module. If the refcnt is
+            not 0, it will sleep 1 second and check the refcnt again, and repeat
+            this until an error is found or the refcnt is 0. You can send a signal
+            to this command if you do not want to wait anymore.
+          </para>
+          <para>
+            Removing modules may be done by test infrastruture code, it can also
+            be done to remove a live kernel patch.
+          </para>
+        </listitem>
+      </varlistentry>
       <varlistentry>
         <term>
           <option>-s</option>

@@ -56,11 +56,13 @@ static int strip_modversion = 0;
 static int strip_vermagic = 0;
 static int remove_dependencies = 0;
 static int quiet_inuse = 0;
+static int do_remove_patient = 0;
 
-static const char cmdopts_s[] = "arRibfDcnC:d:S:sqvVh";
+static const char cmdopts_s[] = "arpRibfDcnC:d:S:sqvVh";
 static const struct option cmdopts[] = {
 	{"all", no_argument, 0, 'a'},
 	{"remove", no_argument, 0, 'r'},
+	{"remove-patiently", no_argument, 0, 'p'},
 	{"remove-dependencies", no_argument, 0, 5},
 	{"resolve-alias", no_argument, 0, 'R'},
 	{"first-time", no_argument, 0, 3},

@@ -107,6 +109,7 @@ static void help(void)
 		"\t                            be a module name to be inserted\n"
 		"\t                            or removed (-r)\n"
 		"\t-r, --remove                Remove modules instead of inserting\n"
+		"\t-p, --remove-patiently      Patiently wait until the refcnt is 0 to remove\n"
 		"\t    --remove-dependencies   Also remove modules depending on it\n"
 		"\t-R, --resolve-alias         Only lookup and print alias and exit\n"
 		"\t    --first-time            Fail if module already inserted or removed\n"

@@ -424,7 +427,7 @@ static int rmmod_do_module(struct kmod_module *mod, int flags)
 	}
 
 	if (!ignore_loaded && !cmd) {
-		int usage = kmod_module_get_refcnt(mod);
+		int usage = kmod_module_get_refcnt_wait(mod, do_remove_patient);
 
 		if (usage > 0) {
 			if (!quiet_inuse)

@@ -785,6 +788,10 @@ static int do_modprobe(int argc, char **orig_argv)
 		case 'r':
 			do_remove = 1;
 			break;
+		case 'p':
+			do_remove = 1;
+			do_remove_patient = 1;
+			break;
 		case 5:
 			remove_dependencies = 1;
 			break;

@@ -27,9 +27,12 @@
 
 #include "kmod.h"
 
-static const char cmdopts_s[] = "h";
+static int do_remove_patient = 0;
+
+static const char cmdopts_s[] = "hp";
 static const struct option cmdopts[] = {
 	{"help", no_argument, 0, 'h'},
+	{"remove-patiently", no_argument, 0, 'p'},
 	{ }
 };
 

@@ -74,7 +77,7 @@ static int check_module_inuse(struct kmod_module *mod) {
 		return -EBUSY;
 	}
 
-	ret = kmod_module_get_refcnt(mod);
+	ret = kmod_module_get_refcnt_wait(mod, do_remove_patient);
 	if (ret > 0) {
 		ERR("Module %s is in use\n", kmod_module_get_name(mod));
 		return -EBUSY;

@@ -101,6 +104,9 @@ static int do_remove(int argc, char *argv[])
 		case 'h':
 			help();
 			return EXIT_SUCCESS;
+		case 'p':
+			do_remove_patient = 1;
+			break;
 
 		default:
 			ERR("Unexpected getopt_long() value '%c'.\n", c);

@@ -35,10 +35,12 @@
 #define DEFAULT_VERBOSE LOG_ERR
 static int verbose = DEFAULT_VERBOSE;
 static int use_syslog;
+static int do_remove_patient;
 
-static const char cmdopts_s[] = "fsvVwh";
+static const char cmdopts_s[] = "fpsvVwh";
 static const struct option cmdopts[] = {
 	{"force", no_argument, 0, 'f'},
+	{"remove-patiently", no_argument, 0, 'p'},
 	{"syslog", no_argument, 0, 's'},
 	{"verbose", no_argument, 0, 'v'},
 	{"version", no_argument, 0, 'V'},

@@ -93,7 +95,7 @@ static int check_module_inuse(struct kmod_module *mod) {
 		return -EBUSY;
 	}
 
-	ret = kmod_module_get_refcnt(mod);
+	ret = kmod_module_get_refcnt_wait(mod, do_remove_patient);
 	if (ret > 0) {
 		ERR("Module %s is in use\n", kmod_module_get_name(mod));
 		return -EBUSY;

@@ -120,6 +122,9 @@ static int do_rmmod(int argc, char *argv[])
 		case 'f':
 			flags |= KMOD_REMOVE_FORCE;
 			break;
+		case 'p':
+			do_remove_patient = 1;
+			break;
 		case 's':
 			use_syslog = 1;
 			break;