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 <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Alan Cox <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Linus Walleij <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
josf · Jul 17, 2017 · 8a932f7 · 8a932f7
1 parent a5d31a3
commit 8a932f7
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Showing 3 changed files with 18 additions and 9 deletions.
diff --git 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;

diff --git a/fs/proc/devices.c b/fs/proc/devices.c
@@ -7,14 +7,14 @@ static int devinfo_show(struct seq_file *f, void *v)
 {
 	int i = *(loff_t *) v;
 
-	if (i < CHRDEV_MAJOR_HASH_SIZE) {
+	if (i < CHRDEV_MAJOR_MAX) {
 		if (i == 0)
 			seq_puts(f, "Character devices:\n");
 		chrdev_show(f, i);
 	}
 #ifdef CONFIG_BLOCK
 	else {
-		i -= CHRDEV_MAJOR_HASH_SIZE;
+		i -= CHRDEV_MAJOR_MAX;
 		if (i == 0)
 			seq_puts(f, "\nBlock devices:\n");
 		blkdev_show(f, i);
@@ -25,15 +25,15 @@ static int devinfo_show(struct seq_file *f, void *v)
 
 static void *devinfo_start(struct seq_file *f, loff_t *pos)
 {
-	if (*pos < (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_HASH_SIZE))
+	if (*pos < (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_MAX))
 		return pos;
 	return NULL;
 }
 
 static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos)
 {
 	(*pos)++;
-	if (*pos >= (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_HASH_SIZE))
+	if (*pos >= (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_MAX))
 		return NULL;
 	return pos;
 }

diff --git a/include/linux/fs.h b/include/linux/fs.h
@@ -2470,7 +2470,7 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev,
 #endif
 
 /* fs/char_dev.c */
-#define CHRDEV_MAJOR_HASH_SIZE	255
+#define CHRDEV_MAJOR_MAX 512
 /* Marks the bottom of the first segment of free char majors */
 #define CHRDEV_MAJOR_DYN_END 234
 /* Marks the top and bottom of the second segment of free char majors */