From: Rusty Russell rusty@rustcorp.com.au

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.

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 --- include/linux/idr.h | 4 +++ lib/idr.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+), 0 deletions(-)

diff --git a/include/linux/idr.h b/include/linux/idr.h index 13a801f..255491c 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -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__ */ diff --git a/lib/idr.c b/lib/idr.c index e15502e..db040ce 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -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) { @@ -926,6 +928,71 @@ 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 *