1 files changed, 41 insertions, 17 deletions

diff --git a/fs/char_dev.c b/fs/char_dev.c
index fb8507f521b2..ebcc8fb3fa66 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -28,6 +28,8 @@ static struct kobj_map *cdev_map;
 
 static DEFINE_MUTEX(chrdevs_lock);
 
+#define CHRDEV_MAJOR_HASH_SIZE 255
+
 static struct char_device_struct {
 	struct char_device_struct *next;
 	unsigned int major;
@@ -49,16 +51,39 @@ void chrdev_show(struct seq_file *f, off_t offset)
 {
 	struct char_device_struct *cd;
 
-	if (offset < CHRDEV_MAJOR_HASH_SIZE) {
-		mutex_lock(&chrdevs_lock);
-		for (cd = chrdevs[offset]; cd; cd = cd->next)
+	mutex_lock(&chrdevs_lock);
+	for (cd = chrdevs[major_to_index(offset)]; cd; cd = cd->next) {
+		if (cd->major == offset)
 			seq_printf(f, "%3d %s\n", cd->major, cd->name);
-		mutex_unlock(&chrdevs_lock);
 	}
+	mutex_unlock(&chrdevs_lock);
 }
 
 #endif /* CONFIG_PROC_FS */
 
+static int find_dynamic_major(void)
+{
+	int i;
+	struct char_device_struct *cd;
+
+	for (i = ARRAY_SIZE(chrdevs)-1; i > CHRDEV_MAJOR_DYN_END; i--) {
+		if (chrdevs[i] == NULL)
+			return i;
+	}
+
+	for (i = CHRDEV_MAJOR_DYN_EXT_START;
+	     i > CHRDEV_MAJOR_DYN_EXT_END; i--) {
+		for (cd = chrdevs[major_to_index(i)]; cd; cd = cd->next)
+			if (cd->major == i)
+				break;
+
+		if (cd == NULL || cd->major != i)
+			return i;
+	}
+
+	return -EBUSY;
+}
+
 /*
  * Register a single major with a specified minor range.
  *
@@ -84,22 +109,21 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
 
 	mutex_lock(&chrdevs_lock);
 
-	/* temporary */
 	if (major == 0) {
-		for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
-			if (chrdevs[i] == NULL)
-				break;
-		}
-
-		if (i < CHRDEV_MAJOR_DYN_END)
-			pr_warn("CHRDEV \"%s\" major number %d goes below the dynamic allocation range\n",
-				name, i);
-
-		if (i == 0) {
-			ret = -EBUSY;
+		ret = find_dynamic_major();
+		if (ret < 0) {
+			pr_err("CHRDEV \"%s\" dynamic allocation region is full\n",
+			       name);
 			goto out;
 		}
-		major = i;
+		major = ret;
+	}
+
+	if (major >= CHRDEV_MAJOR_MAX) {
+		pr_err("CHRDEV \"%s\" major requested (%d) is greater than the maximum (%d)\n",
+		       name, major, CHRDEV_MAJOR_MAX);
+		ret = -EINVAL;
+		goto out;
 	}
 
 	cd->major = major;