[dm-devel] [PATCH] 5/5: Remove 1024 device limit
Kevin Corry
kevcorry at us.ibm.com
Tue Jun 29 19:34:08 UTC 2004
On Monday 21 June 2004 5:57 pm, Kevin Corry wrote:
> Remove the limitation of 1024 DM devices. Each time the minor_bits array
> fills up, allocate a new minor_bits array double the size of the existing
> one.
New version based on feedback from agk.
Remove the limitation of 1024 DM devices.
--- diff/drivers/md/dm.c 2004-06-29 13:22:25.000000000 -0500
+++ source/drivers/md/dm.c 2004-06-29 14:27:32.000000000 -0500
@@ -17,11 +17,13 @@
#include <linux/slab.h>
static const char *_name = DM_NAME;
-#define MAX_DEVICES 1024
static unsigned int major = 0;
static unsigned int _major = 0;
+static int realloc_minor_bits(unsigned long requested_minor);
+static void free_minor_bits(void);
+
/*
* One of these is allocated per bio.
*/
@@ -111,11 +113,19 @@
return -ENOMEM;
}
+ r = realloc_minor_bits(1024);
+ if (r < 0) {
+ kmem_cache_destroy(_tio_cache);
+ kmem_cache_destroy(_io_cache);
+ return r;
+ }
+
_major = major;
r = register_blkdev(_major, _name);
if (r < 0) {
kmem_cache_destroy(_tio_cache);
kmem_cache_destroy(_io_cache);
+ free_minor_bits();
return r;
}
@@ -129,6 +139,7 @@
{
kmem_cache_destroy(_tio_cache);
kmem_cache_destroy(_io_cache);
+ free_minor_bits();
if (unregister_blkdev(_major, _name) < 0)
DMERR("devfs_unregister_blkdev failed");
@@ -615,14 +626,75 @@
/*-----------------------------------------------------------------
* A bitset is used to keep track of allocated minor numbers.
*---------------------------------------------------------------*/
-static spinlock_t _minor_lock = SPIN_LOCK_UNLOCKED;
-static unsigned long _minor_bits[MAX_DEVICES / BITS_PER_LONG];
+static DECLARE_MUTEX(_minor_lock);
+static unsigned long *_minor_bits = NULL;
+static unsigned long _max_minors = 0;
+
+unsigned long pow2_round_up(unsigned long value)
+{
+ unsigned long mask = 1;
+
+ if ((value & (value - 1)) == 0)
+ return value;
+
+ value <<= 1;
+ while (value & (value - 1)) {
+ value &= ~mask;
+ mask <<= 1;
+ }
+
+ return value;
+}
+
+static int realloc_minor_bits(unsigned long requested_minor)
+{
+ unsigned long max_minors;
+ unsigned long *minor_bits, *tmp;
+
+ if (requested_minor < _max_minors)
+ return -EINVAL;
+
+ /* Round up the requested minor to the next power-of-2. */
+ max_minors = pow2_round_up(requested_minor);
+ if (max_minors > (1 << MINORBITS))
+ return -EINVAL;
+
+ minor_bits = kmalloc((max_minors / BITS_PER_LONG) *
+ sizeof(unsigned long), GFP_KERNEL);
+ if (!minor_bits)
+ return -ENOMEM;
+ memset(minor_bits, 0,
+ (max_minors / BITS_PER_LONG) * sizeof(unsigned long));
+
+ /* Copy the existing bit-set to the new one. */
+ if (_minor_bits)
+ memcpy(minor_bits, _minor_bits,
+ ((_max_minors / BITS_PER_LONG) * sizeof(unsigned long)));
+
+ tmp = _minor_bits;
+ _minor_bits = minor_bits;
+ _max_minors = max_minors;
+ if (tmp)
+ kfree(tmp);
+
+ return 0;
+}
+
+static void free_minor_bits(void)
+{
+ down(&_minor_lock);
+ kfree(_minor_bits);
+ _minor_bits = NULL;
+ _max_minors = 0;
+ up(&_minor_lock);
+}
static void free_minor(unsigned int minor)
{
- spin_lock(&_minor_lock);
- clear_bit(minor, _minor_bits);
- spin_unlock(&_minor_lock);
+ down(&_minor_lock);
+ if (minor < _max_minors)
+ clear_bit(minor, _minor_bits);
+ up(&_minor_lock);
}
/*
@@ -630,37 +702,48 @@
*/
static int specific_minor(unsigned int minor)
{
- int r = -EBUSY;
+ int r = 0;
- if (minor >= MAX_DEVICES) {
- DMWARN("request for a mapped_device beyond MAX_DEVICES (%d)",
- MAX_DEVICES);
- return -EINVAL;
+ if (minor > (1 << MINORBITS))
+ return EINVAL;
+
+ down(&_minor_lock);
+ if (minor >= _max_minors) {
+ r = realloc_minor_bits(minor);
+ if (r) {
+ up(&_minor_lock);
+ return r;
+ }
}
- spin_lock(&_minor_lock);
- if (!test_and_set_bit(minor, _minor_bits))
- r = 0;
- spin_unlock(&_minor_lock);
+ if (test_and_set_bit(minor, _minor_bits))
+ r = -EBUSY;
+ up(&_minor_lock);
return r;
}
static int next_free_minor(unsigned int *minor)
{
- int r = -EBUSY;
+ int r;
unsigned int m;
- spin_lock(&_minor_lock);
- m = find_first_zero_bit(_minor_bits, MAX_DEVICES);
- if (m != MAX_DEVICES) {
- set_bit(m, _minor_bits);
- *minor = m;
- r = 0;
+ down(&_minor_lock);
+ m = find_first_zero_bit(_minor_bits, _max_minors);
+ if (m >= _max_minors) {
+ r = realloc_minor_bits(_max_minors * 2);
+ if (r) {
+ up(&_minor_lock);
+ return r;
+ }
+ m = find_first_zero_bit(_minor_bits, _max_minors);
}
- spin_unlock(&_minor_lock);
- return r;
+ set_bit(m, _minor_bits);
+ *minor = m;
+ up(&_minor_lock);
+
+ return 0;
}
static struct block_device_operations dm_blk_dops;
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