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char_dev: order /proc/devices by major number

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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>
This commit is contained in:
Logan Gunthorpe 2017-06-15 14:05:21 -06:00 committed by Greg Kroah-Hartman
parent a5d31a3f81
commit 8a932f73e5
3 changed files with 18 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
fs/char_dev.c
View File

@ -28,6 +28,8 @@ static struct kobj_map *cdev_map;
static DEFINE_MUTEX(chrdevs_lock); static DEFINE_MUTEX(chrdevs_lock);
#define CHRDEV_MAJOR_HASH_SIZE 255
static struct char_device_struct { static struct char_device_struct {
struct char_device_struct *next; struct char_device_struct *next;
unsigned int major; unsigned int major;
@ -49,12 +51,12 @@ void chrdev_show(struct seq_file *f, off_t offset)
{ {
struct char_device_struct *cd; struct char_device_struct *cd;
if (offset < CHRDEV_MAJOR_HASH_SIZE) { mutex_lock(&chrdevs_lock);
mutex_lock(&chrdevs_lock); for (cd = chrdevs[major_to_index(offset)]; cd; cd = cd->next) {
for (cd = chrdevs[offset]; cd; cd = cd->next) if (cd->major == offset)
seq_printf(f, "%3d %s\n", cd->major, cd->name); seq_printf(f, "%3d %s\n", cd->major, cd->name);
mutex_unlock(&chrdevs_lock);
} }
mutex_unlock(&chrdevs_lock);
} }
#endif /* CONFIG_PROC_FS */ #endif /* CONFIG_PROC_FS */
@ -117,6 +119,13 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
major = ret; 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->major = major;
cd->baseminor = baseminor; cd->baseminor = baseminor;
cd->minorct = minorct; cd->minorct = minorct;

8
fs/proc/devices.c
View File

@ -7,14 +7,14 @@ static int devinfo_show(struct seq_file *f, void *v)
{ {
int i = *(loff_t *) v; int i = *(loff_t *) v;
if (i < CHRDEV_MAJOR_HASH_SIZE) { if (i < CHRDEV_MAJOR_MAX) {
if (i == 0) if (i == 0)
seq_puts(f, "Character devices:\n"); seq_puts(f, "Character devices:\n");
chrdev_show(f, i); chrdev_show(f, i);
} }
#ifdef CONFIG_BLOCK #ifdef CONFIG_BLOCK
else { else {
i -= CHRDEV_MAJOR_HASH_SIZE; i -= CHRDEV_MAJOR_MAX;
if (i == 0) if (i == 0)
seq_puts(f, "\nBlock devices:\n"); seq_puts(f, "\nBlock devices:\n");
blkdev_show(f, i); blkdev_show(f, i);
@ -25,7 +25,7 @@ static int devinfo_show(struct seq_file *f, void *v)
static void *devinfo_start(struct seq_file *f, loff_t *pos) 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 pos;
return NULL; return NULL;
} }
@ -33,7 +33,7 @@ static void *devinfo_start(struct seq_file *f, loff_t *pos)
static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos) static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos)
{ {
(*pos)++; (*pos)++;
if (*pos >= (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_HASH_SIZE)) if (*pos >= (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_MAX))
return NULL; return NULL;
return pos; return pos;
} }

2
include/linux/fs.h
View File

@ -2470,7 +2470,7 @@ static inline void bd_unlink_disk_holder(struct block_device *bdev,
#endif #endif
/* fs/char_dev.c */ /* 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 */ /* Marks the bottom of the first segment of free char majors */
#define CHRDEV_MAJOR_DYN_END 234 #define CHRDEV_MAJOR_DYN_END 234
/* Marks the top and bottom of the second segment of free char majors */ /* Marks the top and bottom of the second segment of free char majors */