231 lines
6.7 KiB
C
231 lines
6.7 KiB
C
/*
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* include/linux/idr.h
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*
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* 2002-10-18 written by Jim Houston jim.houston@ccur.com
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* Copyright (C) 2002 by Concurrent Computer Corporation
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* Distributed under the GNU GPL license version 2.
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*
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* Small id to pointer translation service avoiding fixed sized
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* tables.
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*/
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#ifndef __IDR_H__
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#define __IDR_H__
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#include <linux/types.h>
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#include <linux/bitops.h>
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#include <linux/init.h>
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#include <linux/rcupdate.h>
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/*
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* Using 6 bits at each layer allows us to allocate 7 layers out of each page.
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* 8 bits only gave us 3 layers out of every pair of pages, which is less
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* efficient except for trees with a largest element between 192-255 inclusive.
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*/
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#define IDR_BITS 6
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#define IDR_SIZE (1 << IDR_BITS)
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#define IDR_MASK ((1 << IDR_BITS)-1)
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struct idr_layer {
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int prefix; /* the ID prefix of this idr_layer */
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int layer; /* distance from leaf */
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struct idr_layer __rcu *ary[1<<IDR_BITS];
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int count; /* When zero, we can release it */
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union {
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/* A zero bit means "space here" */
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DECLARE_BITMAP(bitmap, IDR_SIZE);
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struct rcu_head rcu_head;
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};
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};
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struct idr {
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struct idr_layer __rcu *hint; /* the last layer allocated from */
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struct idr_layer __rcu *top;
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int layers; /* only valid w/o concurrent changes */
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int cur; /* current pos for cyclic allocation */
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spinlock_t lock;
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int id_free_cnt;
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struct idr_layer *id_free;
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};
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#define IDR_INIT(name) \
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{ \
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.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
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}
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#define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
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/**
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* idr_get_cursor - Return the current position of the cyclic allocator
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* @idr: idr handle
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*
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* The value returned is the value that will be next returned from
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* idr_alloc_cyclic() if it is free (otherwise the search will start from
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* this position).
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*/
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static inline unsigned int idr_get_cursor(struct idr *idr)
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{
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return READ_ONCE(idr->cur);
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}
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/**
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* idr_set_cursor - Set the current position of the cyclic allocator
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* @idr: idr handle
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* @val: new position
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*
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* The next call to idr_alloc_cyclic() will return @val if it is free
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* (otherwise the search will start from this position).
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*/
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static inline void idr_set_cursor(struct idr *idr, unsigned int val)
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{
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WRITE_ONCE(idr->cur, val);
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}
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/**
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* DOC: idr sync
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* idr synchronization (stolen from radix-tree.h)
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*
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* idr_find() is able to be called locklessly, using RCU. The caller must
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* ensure calls to this function are made within rcu_read_lock() regions.
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* Other readers (lock-free or otherwise) and modifications may be running
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* concurrently.
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*
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* It is still required that the caller manage the synchronization and
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* lifetimes of the items. So if RCU lock-free lookups are used, typically
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* this would mean that the items have their own locks, or are amenable to
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* lock-free access; and that the items are freed by RCU (or only freed after
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* having been deleted from the idr tree *and* a synchronize_rcu() grace
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* period).
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*/
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/*
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* This is what we export.
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*/
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void *idr_find_slowpath(struct idr *idp, int id);
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void idr_preload(gfp_t gfp_mask);
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int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
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int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
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int idr_for_each(struct idr *idp,
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int (*fn)(int id, void *p, void *data), void *data);
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void *idr_get_next(struct idr *idp, int *nextid);
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void *idr_replace(struct idr *idp, void *ptr, int id);
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void idr_remove(struct idr *idp, int id);
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void idr_destroy(struct idr *idp);
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void idr_init(struct idr *idp);
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bool idr_is_empty(struct idr *idp);
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/**
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* idr_preload_end - end preload section started with idr_preload()
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*
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* Each idr_preload() should be matched with an invocation of this
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* function. See idr_preload() for details.
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*/
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static inline void idr_preload_end(void)
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{
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preempt_enable();
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}
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/**
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* idr_find - return pointer for given id
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* @idr: idr handle
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* @id: lookup key
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*
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* Return the pointer given the id it has been registered with. A %NULL
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* return indicates that @id is not valid or you passed %NULL in
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* idr_get_new().
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*
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* This function can be called under rcu_read_lock(), given that the leaf
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* pointers lifetimes are correctly managed.
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*/
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static inline void *idr_find(struct idr *idr, int id)
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{
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struct idr_layer *hint = rcu_dereference_raw(idr->hint);
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if (hint && (id & ~IDR_MASK) == hint->prefix)
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return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
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return idr_find_slowpath(idr, id);
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}
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/**
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* idr_for_each_entry - iterate over an idr's elements of a given type
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* @idp: idr handle
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* @entry: the type * to use as cursor
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* @id: id entry's key
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*
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* @entry and @id do not need to be initialized before the loop, and
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* after normal terminatinon @entry is left with the value NULL. This
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* is convenient for a "not found" value.
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*/
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#define idr_for_each_entry(idp, entry, id) \
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for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
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/**
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* idr_for_each_entry - continue iteration over an idr's elements of a given type
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* @idp: idr handle
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* @entry: the type * to use as cursor
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* @id: id entry's key
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*
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* Continue to iterate over list of given type, continuing after
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* the current position.
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*/
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#define idr_for_each_entry_continue(idp, entry, id) \
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for ((entry) = idr_get_next((idp), &(id)); \
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entry; \
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++id, (entry) = idr_get_next((idp), &(id)))
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/*
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* IDA - IDR based id allocator, use when translation from id to
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* pointer isn't necessary.
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*
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* IDA_BITMAP_LONGS is calculated to be one less to accommodate
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* ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
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*/
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#define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
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#define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
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#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
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struct ida_bitmap {
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long nr_busy;
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unsigned long bitmap[IDA_BITMAP_LONGS];
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};
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struct ida {
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struct idr idr;
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struct ida_bitmap *free_bitmap;
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};
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#define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
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#define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
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int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
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int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
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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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/**
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* ida_get_new - allocate new ID
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* @ida: idr handle
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* @p_id: pointer to the allocated handle
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*
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* Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
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*/
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static inline int ida_get_new(struct ida *ida, int *p_id)
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{
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return ida_get_new_above(ida, 0, p_id);
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}
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static inline bool ida_is_empty(struct ida *ida)
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{
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return idr_is_empty(&ida->idr);
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}
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void __init idr_init_cache(void);
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#endif /* __IDR_H__ */
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