char_dev: order /proc/devices by major number

Presently, the order of the char devices listed in /proc/devices is not
entirely sequential. If a char device has a major number greater than
CHRDEV_MAJOR_HASH_SIZE (255), it will be ordered as if its major were
module 255. For example, 511 appears after 1.

This patch cleans that up and prints each major number in the correct
order, regardless of where they are stored in the hash table.

In order to do this, we introduce CHRDEV_MAJOR_MAX as an artificial
limit (chosen to be 511). It will then print all devices in major
order number from 0 to the maximum.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 4 deletions

diff --git a/fs/char_dev.c b/fs/char_dev.c
index c9d18362e89d..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;
@@ -49,12 +51,12 @@ 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 */
@@ -117,6 +119,13 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
 		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;
 	cd->baseminor = baseminor;
 	cd->minorct = minorct;