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Commit 54616283 authored by Tejun Heo's avatar Tejun Heo Committed by Linus Torvalds
Browse files

idr: add idr_layer->prefix 



Add a field which carries the prefix of ID the idr_layer covers.  This
will be used to implement lookup hint.

This patch doesn't make use of the new field and doesn't introduce any
behavior difference.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 050a6b47

include/linux/idr.h

+1 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#define IDR_MASK ((1 << IDR_BITS)-1)



struct idr_layer {

	int			prefix;	/* the ID prefix of this idr_layer */

	DECLARE_BITMAP(bitmap, IDR_SIZE); /* A zero bit means "space here" */

	struct idr_layer __rcu	*ary[1<<IDR_BITS];

	int			count;	/* When zero, we can release it */

lib/idr.c

+13 −0
Original line number Diff line number Diff line
@@ -60,6 +60,16 @@ static int idr_max(int layers) 
	return (1 << bits) - 1;

}



/*

 * Prefix mask for an idr_layer at @layer.  For layer 0, the prefix mask is

 * all bits except for the lower IDR_BITS.  For layer 1, 2 * IDR_BITS, and

 * so on.

 */

static int idr_layer_prefix_mask(int layer)

{

	return ~idr_max(layer + 1);

}



static struct idr_layer *get_from_free_list(struct idr *idp)

{

	struct idr_layer *p;
@@ -272,6 +282,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa, 
			if (!new)

				return -ENOMEM;

			new->layer = l-1;

			new->prefix = id & idr_layer_prefix_mask(new->layer);

			rcu_assign_pointer(p->ary[m], new);

			p->count++;

		}
@@ -313,6 +324,7 @@ static int idr_get_empty_slot(struct idr *idp, int starting_id, 
			 * upwards.

			 */

			p->layer++;

			WARN_ON_ONCE(p->prefix);

			continue;

		}

		if (!(new = idr_layer_alloc(gfp_mask, layer_idr))) {
@@ -334,6 +346,7 @@ static int idr_get_empty_slot(struct idr *idp, int starting_id, 
		new->ary[0] = p;

		new->count = 1;

		new->layer = layers-1;

		new->prefix = id & idr_layer_prefix_mask(new->layer);

		if (bitmap_full(p->bitmap, IDR_SIZE))

			__set_bit(0, new->bitmap);

		p = new;