diff options
| -rw-r--r-- | include/linux/idr.h | 29 | ||||
| -rw-r--r-- | lib/idr.c | 245 |
2 files changed, 274 insertions, 0 deletions
diff --git a/include/linux/idr.h b/include/linux/idr.h index 826803449db7..915572fa030b 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -83,4 +83,33 @@ void idr_remove(struct idr *idp, int id); void idr_destroy(struct idr *idp); void idr_init(struct idr *idp); + +/* + * IDA - IDR based id allocator, use when translation from id to + * pointer isn't necessary. + */ +#define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ +#define IDA_BITMAP_LONGS (128 / sizeof(long) - 1) +#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) + +struct ida_bitmap { + long nr_busy; + unsigned long bitmap[IDA_BITMAP_LONGS]; +}; + +struct ida { + struct idr idr; + struct ida_bitmap *free_bitmap; +}; + +#define IDA_INIT(name) { .idr = IDR_INIT(name), .free_bitmap = NULL, } +#define DEFINE_IDA(name) struct ida name = IDA_INIT(name) + +int ida_pre_get(struct ida *ida, gfp_t gfp_mask); +int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); +int ida_get_new(struct ida *ida, int *p_id); +void ida_remove(struct ida *ida, int id); +void ida_destroy(struct ida *ida); +void ida_init(struct ida *ida); + #endif /* __IDR_H__ */ diff --git a/lib/idr.c b/lib/idr.c index 30b33e2e7a50..b98f01a2eb94 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -506,3 +506,248 @@ void idr_init(struct idr *idp) spin_lock_init(&idp->lock); } EXPORT_SYMBOL(idr_init); + + +/* + * IDA - IDR based ID allocator + * + * this is id allocator without id -> pointer translation. Memory + * usage is much lower than full blown idr because each id only + * occupies a bit. ida uses a custom leaf node which contains + * IDA_BITMAP_BITS slots. + * + * 2007-04-25 written by Tejun Heo <htejun@gmail.com> + */ + +static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap) +{ + unsigned long flags; + + if (!ida->free_bitmap) { + spin_lock_irqsave(&ida->idr.lock, flags); + if (!ida->free_bitmap) { + ida->free_bitmap = bitmap; + bitmap = NULL; + } + spin_unlock_irqrestore(&ida->idr.lock, flags); + } + + kfree(bitmap); +} + +/** + * ida_pre_get - reserve resources for ida allocation + * @ida: ida handle + * @gfp_mask: memory allocation flag + * + * This function should be called prior to locking and calling the + * following function. It preallocates enough memory to satisfy the + * worst possible allocation. + * + * If the system is REALLY out of memory this function returns 0, + * otherwise 1. + */ +int ida_pre_get(struct ida *ida, gfp_t gfp_mask) +{ + /* allocate idr_layers */ + if (!idr_pre_get(&ida->idr, gfp_mask)) + return 0; + + /* allocate free_bitmap */ + if (!ida->free_bitmap) { + struct ida_bitmap *bitmap; + + bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask); + if (!bitmap) + return 0; + + free_bitmap(ida, bitmap); + } + + return 1; +} +EXPORT_SYMBOL(ida_pre_get); + +/** + * ida_get_new_above - allocate new ID above or equal to a start id + * @ida: ida handle + * @staring_id: id to start search at + * @p_id: pointer to the allocated handle + * + * Allocate new ID above or equal to @ida. It should be called with + * any required locks. + * + * If memory is required, it will return -EAGAIN, you should unlock + * and go back to the ida_pre_get() call. If the ida is full, it will + * return -ENOSPC. + * + * @p_id returns a value in the range 0 ... 0x7fffffff. + */ +int ida_get_new_above(struct ida *ida, int starting_id, int *p_id) +{ + struct idr_layer *pa[MAX_LEVEL]; + struct ida_bitmap *bitmap; + unsigned long flags; + int idr_id = starting_id / IDA_BITMAP_BITS; + int offset = starting_id % IDA_BITMAP_BITS; + int t, id; + + restart: + /* get vacant slot */ + t = idr_get_empty_slot(&ida->idr, idr_id, pa); + if (t < 0) { + if (t == -1) + return -EAGAIN; + else /* will be -3 */ + return -ENOSPC; + } + + if (t * IDA_BITMAP_BITS >= MAX_ID_BIT) + return -ENOSPC; + + if (t != idr_id) + offset = 0; + idr_id = t; + + /* if bitmap isn't there, create a new one */ + bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK]; + if (!bitmap) { + spin_lock_irqsave(&ida->idr.lock, flags); + bitmap = ida->free_bitmap; + ida->free_bitmap = NULL; + spin_unlock_irqrestore(&ida->idr.lock, flags); + + if (!bitmap) + return -EAGAIN; + + memset(bitmap, 0, sizeof(struct ida_bitmap)); + pa[0]->ary[idr_id & IDR_MASK] = (void *)bitmap; + pa[0]->count++; + } + + /* lookup for empty slot */ + t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset); + if (t == IDA_BITMAP_BITS) { + /* no empty slot after offset, continue to the next chunk */ + idr_id++; + offset = 0; + goto restart; + } + + id = idr_id * IDA_BITMAP_BITS + t; + if (id >= MAX_ID_BIT) + return -ENOSPC; + + __set_bit(t, bitmap->bitmap); + if (++bitmap->nr_busy == IDA_BITMAP_BITS) + idr_mark_full(pa, idr_id); + + *p_id = id; + + /* Each leaf node can handle nearly a thousand slots and the + * whole idea of ida is to have small memory foot print. + * Throw away extra resources one by one after each successful + * allocation. + */ + if (ida->idr.id_free_cnt || ida->free_bitmap) { + struct idr_layer *p = alloc_layer(&ida->idr); + if (p) + kmem_cache_free(idr_layer_cache, p); + } + + return 0; +} +EXPORT_SYMBOL(ida_get_new_above); + +/** + * ida_get_new - allocate new ID + * @ida: idr handle + * @p_id: pointer to the allocated handle + * + * Allocate new ID. It should be called with any required locks. + * + * If memory is required, it will return -EAGAIN, you should unlock + * and go back to the idr_pre_get() call. If the idr is full, it will + * return -ENOSPC. + * + * @id returns a value in the range 0 ... 0x7fffffff. + */ +int ida_get_new(struct ida *ida, int *p_id) +{ + return ida_get_new_above(ida, 0, p_id); +} +EXPORT_SYMBOL(ida_get_new); + +/** + * ida_remove - remove the given ID + * @ida: ida handle + * @id: ID to free + */ +void ida_remove(struct ida *ida, int id) +{ + struct idr_layer *p = ida->idr.top; + int shift = (ida->idr.layers - 1) * IDR_BITS; + int idr_id = id / IDA_BITMAP_BITS; + int offset = id % IDA_BITMAP_BITS; + int n; + struct ida_bitmap *bitmap; + + /* clear full bits while looking up the leaf idr_layer */ + while ((shift > 0) && p) { + n = (idr_id >> shift) & IDR_MASK; + __clear_bit(n, &p->bitmap); + p = p->ary[n]; + shift -= IDR_BITS; + } + + if (p == NULL) + goto err; + + n = idr_id & IDR_MASK; + __clear_bit(n, &p->bitmap); + + bitmap = (void *)p->ary[n]; + if (!test_bit(offset, bitmap->bitmap)) + goto err; + + /* update bitmap and remove it if empty */ + __clear_bit(offset, bitmap->bitmap); + if (--bitmap->nr_busy == 0) { + __set_bit(n, &p->bitmap); /* to please idr_remove() */ + idr_remove(&ida->idr, idr_id); + free_bitmap(ida, bitmap); + } + + return; + + err: + printk(KERN_WARNING + "ida_remove called for id=%d which is not allocated.\n", id); +} +EXPORT_SYMBOL(ida_remove); + +/** + * ida_destroy - release all cached layers within an ida tree + * ida: ida handle + */ +void ida_destroy(struct ida *ida) +{ + idr_destroy(&ida->idr); + kfree(ida->free_bitmap); +} +EXPORT_SYMBOL(ida_destroy); + +/** + * ida_init - initialize ida handle + * @ida: ida handle + * + * This function is use to set up the handle (@ida) that you will pass + * to the rest of the functions. + */ +void ida_init(struct ida *ida) +{ + memset(ida, 0, sizeof(struct ida)); + idr_init(&ida->idr); + +} +EXPORT_SYMBOL(ida_init); |