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ida: simplified functions for id allocation 

The current hyper-optimized functions are overkill if you simply want to
allocate an id for a device.  Create versions which use an internal
lock.

In followup patches, numerous drivers are converted to use this
interface.

Thanks to Tejun for feedback.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rusty Russell 2011-08-03 16:21:06 -07:00 committed by Linus Torvalds
parent a7295898a1
commit 88eca0207c
2 changed files with 71 additions and 0 deletions
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4
include/linux/idr.h
View File

@ -146,6 +146,10 @@ void ida_remove(struct ida *ida, int id);
void ida_destroy(struct ida *ida);
void ida_init(struct ida *ida);
int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
gfp_t gfp_mask);
void ida_simple_remove(struct ida *ida, unsigned int id);
void __init idr_init_cache(void);
#endif /* __IDR_H__ */

67
lib/idr.c
View File

@ -34,8 +34,10 @@
#include <linux/err.h>
#include <linux/string.h>
#include <linux/idr.h>
#include <linux/spinlock.h>
static struct kmem_cache *idr_layer_cache;
static DEFINE_SPINLOCK(simple_ida_lock);
static struct idr_layer *get_from_free_list(struct idr *idp)
{
@ -925,6 +927,71 @@ void ida_destroy(struct ida *ida)
}
EXPORT_SYMBOL(ida_destroy);
/**
* ida_simple_get - get a new id.
* @ida: the (initialized) ida.
* @start: the minimum id (inclusive, < 0x8000000)
* @end: the maximum id (exclusive, < 0x8000000 or 0)
* @gfp_mask: memory allocation flags
*
* Allocates an id in the range start <= id < end, or returns -ENOSPC.
* On memory allocation failure, returns -ENOMEM.
*
* Use ida_simple_remove() to get rid of an id.
*/
int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
gfp_t gfp_mask)
{
int ret, id;
unsigned int max;
BUG_ON((int)start < 0);
BUG_ON((int)end < 0);
if (end == 0)
max = 0x80000000;
else {
BUG_ON(end < start);
max = end - 1;
}
again:
if (!ida_pre_get(ida, gfp_mask))
return -ENOMEM;
spin_lock(&simple_ida_lock);
ret = ida_get_new_above(ida, start, &id);
if (!ret) {
if (id > max) {
ida_remove(ida, id);
ret = -ENOSPC;
} else {
ret = id;
}
}
spin_unlock(&simple_ida_lock);
if (unlikely(ret == -EAGAIN))
goto again;
return ret;
}
EXPORT_SYMBOL(ida_simple_get);
/**
* ida_simple_remove - remove an allocated id.
* @ida: the (initialized) ida.
* @id: the id returned by ida_simple_get.
*/
void ida_simple_remove(struct ida *ida, unsigned int id)
{
BUG_ON((int)id < 0);
spin_lock(&simple_ida_lock);
ida_remove(ida, id);
spin_unlock(&simple_ida_lock);
}
EXPORT_SYMBOL(ida_simple_remove);
/**
* ida_init - initialize ida handle
* @ida: ida handle