600 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2#include <linux/bitmap.h>3#include <linux/bug.h>4#include <linux/export.h>5#include <linux/idr.h>6#include <linux/slab.h>7#include <linux/spinlock.h>8#include <linux/xarray.h>9 10/**11 * idr_alloc_u32() - Allocate an ID.12 * @idr: IDR handle.13 * @ptr: Pointer to be associated with the new ID.14 * @nextid: Pointer to an ID.15 * @max: The maximum ID to allocate (inclusive).16 * @gfp: Memory allocation flags.17 *18 * Allocates an unused ID in the range specified by @nextid and @max.19 * Note that @max is inclusive whereas the @end parameter to idr_alloc()20 * is exclusive. The new ID is assigned to @nextid before the pointer21 * is inserted into the IDR, so if @nextid points into the object pointed22 * to by @ptr, a concurrent lookup will not find an uninitialised ID.23 *24 * The caller should provide their own locking to ensure that two25 * concurrent modifications to the IDR are not possible. Read-only26 * accesses to the IDR may be done under the RCU read lock or may27 * exclude simultaneous writers.28 *29 * Return: 0 if an ID was allocated, -ENOMEM if memory allocation failed,30 * or -ENOSPC if no free IDs could be found. If an error occurred,31 * @nextid is unchanged.32 */33int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid,34 unsigned long max, gfp_t gfp)35{36 struct radix_tree_iter iter;37 void __rcu **slot;38 unsigned int base = idr->idr_base;39 unsigned int id = *nextid;40 41 if (WARN_ON_ONCE(!(idr->idr_rt.xa_flags & ROOT_IS_IDR)))42 idr->idr_rt.xa_flags |= IDR_RT_MARKER;43 44 id = (id < base) ? 0 : id - base;45 radix_tree_iter_init(&iter, id);46 slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base);47 if (IS_ERR(slot))48 return PTR_ERR(slot);49 50 *nextid = iter.index + base;51 /* there is a memory barrier inside radix_tree_iter_replace() */52 radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);53 radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);54 55 return 0;56}57EXPORT_SYMBOL_GPL(idr_alloc_u32);58 59/**60 * idr_alloc() - Allocate an ID.61 * @idr: IDR handle.62 * @ptr: Pointer to be associated with the new ID.63 * @start: The minimum ID (inclusive).64 * @end: The maximum ID (exclusive).65 * @gfp: Memory allocation flags.66 *67 * Allocates an unused ID in the range specified by @start and @end. If68 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows69 * callers to use @start + N as @end as long as N is within integer range.70 *71 * The caller should provide their own locking to ensure that two72 * concurrent modifications to the IDR are not possible. Read-only73 * accesses to the IDR may be done under the RCU read lock or may74 * exclude simultaneous writers.75 *76 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,77 * or -ENOSPC if no free IDs could be found.78 */79int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)80{81 u32 id = start;82 int ret;83 84 if (WARN_ON_ONCE(start < 0))85 return -EINVAL;86 87 ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp);88 if (ret)89 return ret;90 91 return id;92}93EXPORT_SYMBOL_GPL(idr_alloc);94 95/**96 * idr_alloc_cyclic() - Allocate an ID cyclically.97 * @idr: IDR handle.98 * @ptr: Pointer to be associated with the new ID.99 * @start: The minimum ID (inclusive).100 * @end: The maximum ID (exclusive).101 * @gfp: Memory allocation flags.102 *103 * Allocates an unused ID in the range specified by @start and @end. If104 * @end is <= 0, it is treated as one larger than %INT_MAX. This allows105 * callers to use @start + N as @end as long as N is within integer range.106 * The search for an unused ID will start at the last ID allocated and will107 * wrap around to @start if no free IDs are found before reaching @end.108 *109 * The caller should provide their own locking to ensure that two110 * concurrent modifications to the IDR are not possible. Read-only111 * accesses to the IDR may be done under the RCU read lock or may112 * exclude simultaneous writers.113 *114 * Return: The newly allocated ID, -ENOMEM if memory allocation failed,115 * or -ENOSPC if no free IDs could be found.116 */117int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)118{119 u32 id = idr->idr_next;120 int err, max = end > 0 ? end - 1 : INT_MAX;121 122 if ((int)id < start)123 id = start;124 125 err = idr_alloc_u32(idr, ptr, &id, max, gfp);126 if ((err == -ENOSPC) && (id > start)) {127 id = start;128 err = idr_alloc_u32(idr, ptr, &id, max, gfp);129 }130 if (err)131 return err;132 133 idr->idr_next = id + 1;134 return id;135}136EXPORT_SYMBOL(idr_alloc_cyclic);137 138/**139 * idr_remove() - Remove an ID from the IDR.140 * @idr: IDR handle.141 * @id: Pointer ID.142 *143 * Removes this ID from the IDR. If the ID was not previously in the IDR,144 * this function returns %NULL.145 *146 * Since this function modifies the IDR, the caller should provide their147 * own locking to ensure that concurrent modification of the same IDR is148 * not possible.149 *150 * Return: The pointer formerly associated with this ID.151 */152void *idr_remove(struct idr *idr, unsigned long id)153{154 return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL);155}156EXPORT_SYMBOL_GPL(idr_remove);157 158/**159 * idr_find() - Return pointer for given ID.160 * @idr: IDR handle.161 * @id: Pointer ID.162 *163 * Looks up the pointer associated with this ID. A %NULL pointer may164 * indicate that @id is not allocated or that the %NULL pointer was165 * associated with this ID.166 *167 * This function can be called under rcu_read_lock(), given that the leaf168 * pointers lifetimes are correctly managed.169 *170 * Return: The pointer associated with this ID.171 */172void *idr_find(const struct idr *idr, unsigned long id)173{174 return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base);175}176EXPORT_SYMBOL_GPL(idr_find);177 178/**179 * idr_for_each() - Iterate through all stored pointers.180 * @idr: IDR handle.181 * @fn: Function to be called for each pointer.182 * @data: Data passed to callback function.183 *184 * The callback function will be called for each entry in @idr, passing185 * the ID, the entry and @data.186 *187 * If @fn returns anything other than %0, the iteration stops and that188 * value is returned from this function.189 *190 * idr_for_each() can be called concurrently with idr_alloc() and191 * idr_remove() if protected by RCU. Newly added entries may not be192 * seen and deleted entries may be seen, but adding and removing entries193 * will not cause other entries to be skipped, nor spurious ones to be seen.194 */195int idr_for_each(const struct idr *idr,196 int (*fn)(int id, void *p, void *data), void *data)197{198 struct radix_tree_iter iter;199 void __rcu **slot;200 int base = idr->idr_base;201 202 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {203 int ret;204 unsigned long id = iter.index + base;205 206 if (WARN_ON_ONCE(id > INT_MAX))207 break;208 ret = fn(id, rcu_dereference_raw(*slot), data);209 if (ret)210 return ret;211 }212 213 return 0;214}215EXPORT_SYMBOL(idr_for_each);216 217/**218 * idr_get_next_ul() - Find next populated entry.219 * @idr: IDR handle.220 * @nextid: Pointer to an ID.221 *222 * Returns the next populated entry in the tree with an ID greater than223 * or equal to the value pointed to by @nextid. On exit, @nextid is updated224 * to the ID of the found value. To use in a loop, the value pointed to by225 * nextid must be incremented by the user.226 */227void *idr_get_next_ul(struct idr *idr, unsigned long *nextid)228{229 struct radix_tree_iter iter;230 void __rcu **slot;231 void *entry = NULL;232 unsigned long base = idr->idr_base;233 unsigned long id = *nextid;234 235 id = (id < base) ? 0 : id - base;236 radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, id) {237 entry = rcu_dereference_raw(*slot);238 if (!entry)239 continue;240 if (!xa_is_internal(entry))241 break;242 if (slot != &idr->idr_rt.xa_head && !xa_is_retry(entry))243 break;244 slot = radix_tree_iter_retry(&iter);245 }246 if (!slot)247 return NULL;248 249 *nextid = iter.index + base;250 return entry;251}252EXPORT_SYMBOL(idr_get_next_ul);253 254/**255 * idr_get_next() - Find next populated entry.256 * @idr: IDR handle.257 * @nextid: Pointer to an ID.258 *259 * Returns the next populated entry in the tree with an ID greater than260 * or equal to the value pointed to by @nextid. On exit, @nextid is updated261 * to the ID of the found value. To use in a loop, the value pointed to by262 * nextid must be incremented by the user.263 */264void *idr_get_next(struct idr *idr, int *nextid)265{266 unsigned long id = *nextid;267 void *entry = idr_get_next_ul(idr, &id);268 269 if (WARN_ON_ONCE(id > INT_MAX))270 return NULL;271 *nextid = id;272 return entry;273}274EXPORT_SYMBOL(idr_get_next);275 276/**277 * idr_replace() - replace pointer for given ID.278 * @idr: IDR handle.279 * @ptr: New pointer to associate with the ID.280 * @id: ID to change.281 *282 * Replace the pointer registered with an ID and return the old value.283 * This function can be called under the RCU read lock concurrently with284 * idr_alloc() and idr_remove() (as long as the ID being removed is not285 * the one being replaced!).286 *287 * Returns: the old value on success. %-ENOENT indicates that @id was not288 * found. %-EINVAL indicates that @ptr was not valid.289 */290void *idr_replace(struct idr *idr, void *ptr, unsigned long id)291{292 struct radix_tree_node *node;293 void __rcu **slot = NULL;294 void *entry;295 296 id -= idr->idr_base;297 298 entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);299 if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))300 return ERR_PTR(-ENOENT);301 302 __radix_tree_replace(&idr->idr_rt, node, slot, ptr);303 304 return entry;305}306EXPORT_SYMBOL(idr_replace);307 308/**309 * DOC: IDA description310 *311 * The IDA is an ID allocator which does not provide the ability to312 * associate an ID with a pointer. As such, it only needs to store one313 * bit per ID, and so is more space efficient than an IDR. To use an IDA,314 * define it using DEFINE_IDA() (or embed a &struct ida in a data structure,315 * then initialise it using ida_init()). To allocate a new ID, call316 * ida_alloc(), ida_alloc_min(), ida_alloc_max() or ida_alloc_range().317 * To free an ID, call ida_free().318 *319 * ida_destroy() can be used to dispose of an IDA without needing to320 * free the individual IDs in it. You can use ida_is_empty() to find321 * out whether the IDA has any IDs currently allocated.322 *323 * The IDA handles its own locking. It is safe to call any of the IDA324 * functions without synchronisation in your code.325 *326 * IDs are currently limited to the range [0-INT_MAX]. If this is an awkward327 * limitation, it should be quite straightforward to raise the maximum.328 */329 330/*331 * Developer's notes:332 *333 * The IDA uses the functionality provided by the XArray to store bitmaps in334 * each entry. The XA_FREE_MARK is only cleared when all bits in the bitmap335 * have been set.336 *337 * I considered telling the XArray that each slot is an order-10 node338 * and indexing by bit number, but the XArray can't allow a single multi-index339 * entry in the head, which would significantly increase memory consumption340 * for the IDA. So instead we divide the index by the number of bits in the341 * leaf bitmap before doing a radix tree lookup.342 *343 * As an optimisation, if there are only a few low bits set in any given344 * leaf, instead of allocating a 128-byte bitmap, we store the bits345 * as a value entry. Value entries never have the XA_FREE_MARK cleared346 * because we can always convert them into a bitmap entry.347 *348 * It would be possible to optimise further; once we've run out of a349 * single 128-byte bitmap, we currently switch to a 576-byte node, put350 * the 128-byte bitmap in the first entry and then start allocating extra351 * 128-byte entries. We could instead use the 512 bytes of the node's352 * data as a bitmap before moving to that scheme. I do not believe this353 * is a worthwhile optimisation; Rasmus Villemoes surveyed the current354 * users of the IDA and almost none of them use more than 1024 entries.355 * Those that do use more than the 8192 IDs that the 512 bytes would356 * provide.357 *358 * The IDA always uses a lock to alloc/free. If we add a 'test_bit'359 * equivalent, it will still need locking. Going to RCU lookup would require360 * using RCU to free bitmaps, and that's not trivial without embedding an361 * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte362 * bitmap, which is excessive.363 */364 365/**366 * ida_alloc_range() - Allocate an unused ID.367 * @ida: IDA handle.368 * @min: Lowest ID to allocate.369 * @max: Highest ID to allocate.370 * @gfp: Memory allocation flags.371 *372 * Allocate an ID between @min and @max, inclusive. The allocated ID will373 * not exceed %INT_MAX, even if @max is larger.374 *375 * Context: Any context. It is safe to call this function without376 * locking in your code.377 * Return: The allocated ID, or %-ENOMEM if memory could not be allocated,378 * or %-ENOSPC if there are no free IDs.379 */380int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,381 gfp_t gfp)382{383 XA_STATE(xas, &ida->xa, min / IDA_BITMAP_BITS);384 unsigned bit = min % IDA_BITMAP_BITS;385 unsigned long flags;386 struct ida_bitmap *bitmap, *alloc = NULL;387 388 if ((int)min < 0)389 return -ENOSPC;390 391 if ((int)max < 0)392 max = INT_MAX;393 394retry:395 xas_lock_irqsave(&xas, flags);396next:397 bitmap = xas_find_marked(&xas, max / IDA_BITMAP_BITS, XA_FREE_MARK);398 if (xas.xa_index > min / IDA_BITMAP_BITS)399 bit = 0;400 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)401 goto nospc;402 403 if (xa_is_value(bitmap)) {404 unsigned long tmp = xa_to_value(bitmap);405 406 if (bit < BITS_PER_XA_VALUE) {407 bit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE, bit);408 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)409 goto nospc;410 if (bit < BITS_PER_XA_VALUE) {411 tmp |= 1UL << bit;412 xas_store(&xas, xa_mk_value(tmp));413 goto out;414 }415 }416 bitmap = alloc;417 if (!bitmap)418 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);419 if (!bitmap)420 goto alloc;421 bitmap->bitmap[0] = tmp;422 xas_store(&xas, bitmap);423 if (xas_error(&xas)) {424 bitmap->bitmap[0] = 0;425 goto out;426 }427 }428 429 if (bitmap) {430 bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit);431 if (xas.xa_index * IDA_BITMAP_BITS + bit > max)432 goto nospc;433 if (bit == IDA_BITMAP_BITS)434 goto next;435 436 __set_bit(bit, bitmap->bitmap);437 if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))438 xas_clear_mark(&xas, XA_FREE_MARK);439 } else {440 if (bit < BITS_PER_XA_VALUE) {441 bitmap = xa_mk_value(1UL << bit);442 } else {443 bitmap = alloc;444 if (!bitmap)445 bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT);446 if (!bitmap)447 goto alloc;448 __set_bit(bit, bitmap->bitmap);449 }450 xas_store(&xas, bitmap);451 }452out:453 xas_unlock_irqrestore(&xas, flags);454 if (xas_nomem(&xas, gfp)) {455 xas.xa_index = min / IDA_BITMAP_BITS;456 bit = min % IDA_BITMAP_BITS;457 goto retry;458 }459 if (bitmap != alloc)460 kfree(alloc);461 if (xas_error(&xas))462 return xas_error(&xas);463 return xas.xa_index * IDA_BITMAP_BITS + bit;464alloc:465 xas_unlock_irqrestore(&xas, flags);466 alloc = kzalloc(sizeof(*bitmap), gfp);467 if (!alloc)468 return -ENOMEM;469 xas_set(&xas, min / IDA_BITMAP_BITS);470 bit = min % IDA_BITMAP_BITS;471 goto retry;472nospc:473 xas_unlock_irqrestore(&xas, flags);474 kfree(alloc);475 return -ENOSPC;476}477EXPORT_SYMBOL(ida_alloc_range);478 479/**480 * ida_free() - Release an allocated ID.481 * @ida: IDA handle.482 * @id: Previously allocated ID.483 *484 * Context: Any context. It is safe to call this function without485 * locking in your code.486 */487void ida_free(struct ida *ida, unsigned int id)488{489 XA_STATE(xas, &ida->xa, id / IDA_BITMAP_BITS);490 unsigned bit = id % IDA_BITMAP_BITS;491 struct ida_bitmap *bitmap;492 unsigned long flags;493 494 if ((int)id < 0)495 return;496 497 xas_lock_irqsave(&xas, flags);498 bitmap = xas_load(&xas);499 500 if (xa_is_value(bitmap)) {501 unsigned long v = xa_to_value(bitmap);502 if (bit >= BITS_PER_XA_VALUE)503 goto err;504 if (!(v & (1UL << bit)))505 goto err;506 v &= ~(1UL << bit);507 if (!v)508 goto delete;509 xas_store(&xas, xa_mk_value(v));510 } else {511 if (!bitmap || !test_bit(bit, bitmap->bitmap))512 goto err;513 __clear_bit(bit, bitmap->bitmap);514 xas_set_mark(&xas, XA_FREE_MARK);515 if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {516 kfree(bitmap);517delete:518 xas_store(&xas, NULL);519 }520 }521 xas_unlock_irqrestore(&xas, flags);522 return;523 err:524 xas_unlock_irqrestore(&xas, flags);525 WARN(1, "ida_free called for id=%d which is not allocated.\n", id);526}527EXPORT_SYMBOL(ida_free);528 529/**530 * ida_destroy() - Free all IDs.531 * @ida: IDA handle.532 *533 * Calling this function frees all IDs and releases all resources used534 * by an IDA. When this call returns, the IDA is empty and can be reused535 * or freed. If the IDA is already empty, there is no need to call this536 * function.537 *538 * Context: Any context. It is safe to call this function without539 * locking in your code.540 */541void ida_destroy(struct ida *ida)542{543 XA_STATE(xas, &ida->xa, 0);544 struct ida_bitmap *bitmap;545 unsigned long flags;546 547 xas_lock_irqsave(&xas, flags);548 xas_for_each(&xas, bitmap, ULONG_MAX) {549 if (!xa_is_value(bitmap))550 kfree(bitmap);551 xas_store(&xas, NULL);552 }553 xas_unlock_irqrestore(&xas, flags);554}555EXPORT_SYMBOL(ida_destroy);556 557#ifndef __KERNEL__558extern void xa_dump_index(unsigned long index, unsigned int shift);559#define IDA_CHUNK_SHIFT ilog2(IDA_BITMAP_BITS)560 561static void ida_dump_entry(void *entry, unsigned long index)562{563 unsigned long i;564 565 if (!entry)566 return;567 568 if (xa_is_node(entry)) {569 struct xa_node *node = xa_to_node(entry);570 unsigned int shift = node->shift + IDA_CHUNK_SHIFT +571 XA_CHUNK_SHIFT;572 573 xa_dump_index(index * IDA_BITMAP_BITS, shift);574 xa_dump_node(node);575 for (i = 0; i < XA_CHUNK_SIZE; i++)576 ida_dump_entry(node->slots[i],577 index | (i << node->shift));578 } else if (xa_is_value(entry)) {579 xa_dump_index(index * IDA_BITMAP_BITS, ilog2(BITS_PER_LONG));580 pr_cont("value: data %lx [%px]\n", xa_to_value(entry), entry);581 } else {582 struct ida_bitmap *bitmap = entry;583 584 xa_dump_index(index * IDA_BITMAP_BITS, IDA_CHUNK_SHIFT);585 pr_cont("bitmap: %p data", bitmap);586 for (i = 0; i < IDA_BITMAP_LONGS; i++)587 pr_cont(" %lx", bitmap->bitmap[i]);588 pr_cont("\n");589 }590}591 592static void ida_dump(struct ida *ida)593{594 struct xarray *xa = &ida->xa;595 pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head,596 xa->xa_flags >> ROOT_TAG_SHIFT);597 ida_dump_entry(xa->xa_head, 0);598}599#endif600