Commit dcbff5d1 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Linus Torvalds

idr: reorder the fields

idr_layer->layer is always accessed in read path, move it in the front.

idr_layer->bitmap is moved on the bottom.  And rcu_head shares with
bitmap due to they do not be accessed at the same time.

idr->id_free/id_free_cnt/lock are free list fields, and moved to the
bottom.  They will be removed in near future.
Signed-off-by: default avatarLai Jiangshan <>
Cc: Tejun Heo <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 15f3ec3f
......@@ -29,21 +29,24 @@
struct idr_layer {
int prefix; /* the ID prefix of this idr_layer */
DECLARE_BITMAP(bitmap, IDR_SIZE); /* A zero bit means "space here" */
int layer; /* distance from leaf */
struct idr_layer __rcu *ary[1<<IDR_BITS];
int count; /* When zero, we can release it */
int layer; /* distance from leaf */
struct rcu_head rcu_head;
union {
/* A zero bit means "space here" */
struct rcu_head rcu_head;
struct idr {
struct idr_layer __rcu *hint; /* the last layer allocated from */
struct idr_layer __rcu *top;
struct idr_layer *id_free;
int layers; /* only valid w/o concurrent changes */
int id_free_cnt;
int cur; /* current pos for cyclic allocation */
spinlock_t lock;
int id_free_cnt;
struct idr_layer *id_free;
#define IDR_INIT(name) \
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