Commit bf98c406 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds

[PATCH] devfs: race fixes and cleanup

From: Andrey Borzenkov <arvidjaar@mail.ru>

- use struct nameidata in devfs_d_revalidate_wait to detect when it is
  called without i_sem hold; take i_sem on parent in this case.  This
  prevents both deadlock with devfs_lookup by allowing it to drop i_sem
  consistently and oops in d_instantiate by ensuring that it always runs
  protected

- remove dead code that deals with major number allocation.  The only
  remaining user was devfs itself and patch changes it to

- use register_chardev to get device number for internal /dev/.devfsd and
  /dev/.statd.

- remove dead auto allocation flag as well

- remove code that does module get on dev open - it is handled by fops_get.
   Use init_special_inode consistently

- get rid of struct cdev_type and bdev_type - both have just single dev_t
  now
parent 01d1a791
This diff is collapsed.
extern dev_t devfs_alloc_devnum(umode_t mode);
extern void devfs_dealloc_devnum(umode_t mode, dev_t devnum);
......@@ -72,7 +72,6 @@
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <asm/bitops.h>
#include "internal.h"
int devfs_register_tape(const char *name)
......@@ -96,161 +95,3 @@ void devfs_unregister_tape(int num)
}
EXPORT_SYMBOL(devfs_unregister_tape);
struct major_list
{
spinlock_t lock;
unsigned long bits[256 / BITS_PER_LONG];
};
#if BITS_PER_LONG == 32
# define INITIALISER64(low,high) (low), (high)
#else
# define INITIALISER64(low,high) ( (unsigned long) (high) << 32 | (low) )
#endif
/* Block majors already assigned:
0-3, 7-9, 11-63, 65-99, 101-113, 120-127, 199, 201, 240-255
Total free: 122
*/
static struct major_list block_major_list =
{SPIN_LOCK_UNLOCKED,
{INITIALISER64 (0xfffffb8f, 0xffffffff), /* Majors 0-31, 32-63 */
INITIALISER64 (0xfffffffe, 0xff03ffef), /* Majors 64-95, 96-127 */
INITIALISER64 (0x00000000, 0x00000000), /* Majors 128-159, 160-191 */
INITIALISER64 (0x00000280, 0xffff0000), /* Majors 192-223, 224-255 */
}
};
/* Char majors already assigned:
0-7, 9-151, 154-158, 160-211, 216-221, 224-230, 240-255
Total free: 19
*/
static struct major_list char_major_list =
{SPIN_LOCK_UNLOCKED,
{INITIALISER64 (0xfffffeff, 0xffffffff), /* Majors 0-31, 32-63 */
INITIALISER64 (0xffffffff, 0xffffffff), /* Majors 64-95, 96-127 */
INITIALISER64 (0x7cffffff, 0xffffffff), /* Majors 128-159, 160-191 */
INITIALISER64 (0x3f0fffff, 0xffff007f), /* Majors 192-223, 224-255 */
}
};
/**
* devfs_alloc_major - Allocate a major number.
* @mode: The file mode (must be block device or character device).
* Returns the allocated major, else -1 if none are available.
* This routine is thread safe and does not block.
*/
struct minor_list
{
int major;
unsigned long bits[256 / BITS_PER_LONG];
struct minor_list *next;
};
static struct device_list {
struct minor_list *first;
struct minor_list *last;
int none_free;
} block_list, char_list;
static DECLARE_MUTEX(device_list_mutex);
/**
* devfs_alloc_devnum - Allocate a device number.
* @mode: The file mode (must be block device or character device).
*
* Returns the allocated device number, else NODEV if none are available.
* This routine is thread safe and may block.
*/
dev_t devfs_alloc_devnum(umode_t mode)
{
struct device_list *list;
struct major_list *major_list;
struct minor_list *entry;
int minor;
if (S_ISCHR(mode)) {
major_list = &char_major_list;
list = &char_list;
} else {
major_list = &block_major_list;
list = &block_list;
}
down(&device_list_mutex);
if (list->none_free)
goto out_unlock;
for (entry = list->first; entry; entry = entry->next) {
minor = find_first_zero_bit (entry->bits, 256);
if (minor >= 256)
continue;
goto out_done;
}
/* Need to allocate a new major */
entry = kmalloc (sizeof *entry, GFP_KERNEL);
if (!entry)
goto out_full;
memset(entry, 0, sizeof *entry);
spin_lock(&major_list->lock);
entry->major = find_first_zero_bit(major_list->bits, 256);
if (entry->major >= 256) {
spin_unlock(&major_list->lock);
kfree(entry);
goto out_full;
}
__set_bit(entry->major, major_list->bits);
spin_unlock(&major_list->lock);
if (!list->first)
list->first = entry;
else
list->last->next = entry;
list->last = entry;
minor = 0;
out_done:
__set_bit(minor, entry->bits);
up(&device_list_mutex);
return MKDEV(entry->major, minor);
out_full:
list->none_free = 1;
out_unlock:
up(&device_list_mutex);
return 0;
}
/**
* devfs_dealloc_devnum - Dellocate a device number.
* @mode: The file mode (must be block device or character device).
* @devnum: The device number.
*
* This routine is thread safe and may block.
*/
void devfs_dealloc_devnum(umode_t mode, dev_t devnum)
{
struct device_list *list = S_ISCHR(mode) ? &char_list : &block_list;
struct minor_list *entry;
if (!devnum)
return;
down(&device_list_mutex);
for (entry = list->first; entry; entry = entry->next) {
if (entry->major == MAJOR(devnum)) {
if (__test_and_clear_bit(MINOR(devnum), entry->bits))
list->none_free = 0;
break;
}
}
up(&device_list_mutex);
}
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