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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>
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@ -146,6 +146,10 @@ void ida_remove(struct ida *ida, int id);
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void ida_destroy(struct ida *ida);
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void ida_init(struct ida *ida);
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int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
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gfp_t gfp_mask);
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void ida_simple_remove(struct ida *ida, unsigned int id);
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void __init idr_init_cache(void);
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#endif /* __IDR_H__ */
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67
lib/idr.c
67
lib/idr.c
@ -34,8 +34,10 @@
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#include <linux/err.h>
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#include <linux/string.h>
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#include <linux/idr.h>
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#include <linux/spinlock.h>
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static struct kmem_cache *idr_layer_cache;
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static DEFINE_SPINLOCK(simple_ida_lock);
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static struct idr_layer *get_from_free_list(struct idr *idp)
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{
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@ -925,6 +927,71 @@ void ida_destroy(struct ida *ida)
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}
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EXPORT_SYMBOL(ida_destroy);
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/**
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* ida_simple_get - get a new id.
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* @ida: the (initialized) ida.
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* @start: the minimum id (inclusive, < 0x8000000)
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* @end: the maximum id (exclusive, < 0x8000000 or 0)
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* @gfp_mask: memory allocation flags
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*
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* Allocates an id in the range start <= id < end, or returns -ENOSPC.
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* On memory allocation failure, returns -ENOMEM.
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*
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* Use ida_simple_remove() to get rid of an id.
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*/
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int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
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gfp_t gfp_mask)
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{
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int ret, id;
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unsigned int max;
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BUG_ON((int)start < 0);
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BUG_ON((int)end < 0);
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if (end == 0)
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max = 0x80000000;
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else {
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BUG_ON(end < start);
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max = end - 1;
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}
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again:
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if (!ida_pre_get(ida, gfp_mask))
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return -ENOMEM;
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spin_lock(&simple_ida_lock);
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ret = ida_get_new_above(ida, start, &id);
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if (!ret) {
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if (id > max) {
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ida_remove(ida, id);
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ret = -ENOSPC;
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} else {
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ret = id;
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}
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}
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spin_unlock(&simple_ida_lock);
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if (unlikely(ret == -EAGAIN))
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goto again;
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return ret;
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}
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EXPORT_SYMBOL(ida_simple_get);
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/**
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* ida_simple_remove - remove an allocated id.
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* @ida: the (initialized) ida.
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* @id: the id returned by ida_simple_get.
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*/
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void ida_simple_remove(struct ida *ida, unsigned int id)
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{
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BUG_ON((int)id < 0);
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spin_lock(&simple_ida_lock);
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ida_remove(ida, id);
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spin_unlock(&simple_ida_lock);
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}
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EXPORT_SYMBOL(ida_simple_remove);
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/**
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* ida_init - initialize ida handle
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* @ida: ida handle
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