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lib/idr.c
17.5 KB
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// SPDX-License-Identifier: GPL-2.0-only |
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#include <linux/bitmap.h> |
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#include <linux/bug.h> |
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#include <linux/export.h> |
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#include <linux/idr.h> |
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#include <linux/slab.h> |
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#include <linux/spinlock.h> |
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#include <linux/xarray.h> |
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/** * idr_alloc_u32() - Allocate an ID. * @idr: IDR handle. * @ptr: Pointer to be associated with the new ID. * @nextid: Pointer to an ID. * @max: The maximum ID to allocate (inclusive). * @gfp: Memory allocation flags. * * Allocates an unused ID in the range specified by @nextid and @max. * Note that @max is inclusive whereas the @end parameter to idr_alloc() |
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* is exclusive. The new ID is assigned to @nextid before the pointer * is inserted into the IDR, so if @nextid points into the object pointed * to by @ptr, a concurrent lookup will not find an uninitialised ID. |
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* * The caller should provide their own locking to ensure that two * concurrent modifications to the IDR are not possible. Read-only * accesses to the IDR may be done under the RCU read lock or may * exclude simultaneous writers. * * Return: 0 if an ID was allocated, -ENOMEM if memory allocation failed, * or -ENOSPC if no free IDs could be found. If an error occurred, * @nextid is unchanged. */ int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid, unsigned long max, gfp_t gfp) { |
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struct radix_tree_iter iter; |
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void __rcu **slot; |
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unsigned int base = idr->idr_base; unsigned int id = *nextid; |
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if (WARN_ON_ONCE(!(idr->idr_rt.xa_flags & ROOT_IS_IDR))) idr->idr_rt.xa_flags |= IDR_RT_MARKER; |
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id = (id < base) ? 0 : id - base; radix_tree_iter_init(&iter, id); slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base); |
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if (IS_ERR(slot)) return PTR_ERR(slot); |
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*nextid = iter.index + base; |
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/* there is a memory barrier inside radix_tree_iter_replace() */ |
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radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr); radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE); |
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return 0; |
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} |
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EXPORT_SYMBOL_GPL(idr_alloc_u32); |
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/** |
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* idr_alloc() - Allocate an ID. * @idr: IDR handle. * @ptr: Pointer to be associated with the new ID. * @start: The minimum ID (inclusive). * @end: The maximum ID (exclusive). * @gfp: Memory allocation flags. |
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* |
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* Allocates an unused ID in the range specified by @start and @end. If * @end is <= 0, it is treated as one larger than %INT_MAX. This allows * callers to use @start + N as @end as long as N is within integer range. * * The caller should provide their own locking to ensure that two * concurrent modifications to the IDR are not possible. Read-only * accesses to the IDR may be done under the RCU read lock or may * exclude simultaneous writers. * * Return: The newly allocated ID, -ENOMEM if memory allocation failed, * or -ENOSPC if no free IDs could be found. |
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*/ |
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int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp) |
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{ |
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u32 id = start; int ret; if (WARN_ON_ONCE(start < 0)) return -EINVAL; ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp); if (ret) return ret; |
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return id; } EXPORT_SYMBOL_GPL(idr_alloc); /** * idr_alloc_cyclic() - Allocate an ID cyclically. * @idr: IDR handle. * @ptr: Pointer to be associated with the new ID. * @start: The minimum ID (inclusive). * @end: The maximum ID (exclusive). * @gfp: Memory allocation flags. * * Allocates an unused ID in the range specified by @nextid and @end. If * @end is <= 0, it is treated as one larger than %INT_MAX. This allows * callers to use @start + N as @end as long as N is within integer range. * The search for an unused ID will start at the last ID allocated and will * wrap around to @start if no free IDs are found before reaching @end. * * The caller should provide their own locking to ensure that two * concurrent modifications to the IDR are not possible. Read-only * accesses to the IDR may be done under the RCU read lock or may * exclude simultaneous writers. * * Return: The newly allocated ID, -ENOMEM if memory allocation failed, * or -ENOSPC if no free IDs could be found. */ int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp) { u32 id = idr->idr_next; int err, max = end > 0 ? end - 1 : INT_MAX; |
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if ((int)id < start) id = start; |
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err = idr_alloc_u32(idr, ptr, &id, max, gfp); if ((err == -ENOSPC) && (id > start)) { id = start; err = idr_alloc_u32(idr, ptr, &id, max, gfp); } if (err) return err; |
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idr->idr_next = id + 1; |
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return id; |
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} |
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EXPORT_SYMBOL(idr_alloc_cyclic); |
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/** |
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* idr_remove() - Remove an ID from the IDR. * @idr: IDR handle. * @id: Pointer ID. * * Removes this ID from the IDR. If the ID was not previously in the IDR, * this function returns %NULL. * * Since this function modifies the IDR, the caller should provide their * own locking to ensure that concurrent modification of the same IDR is * not possible. * * Return: The pointer formerly associated with this ID. */ void *idr_remove(struct idr *idr, unsigned long id) { return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL); } EXPORT_SYMBOL_GPL(idr_remove); /** * idr_find() - Return pointer for given ID. * @idr: IDR handle. * @id: Pointer ID. * * Looks up the pointer associated with this ID. A %NULL pointer may * indicate that @id is not allocated or that the %NULL pointer was * associated with this ID. * * This function can be called under rcu_read_lock(), given that the leaf * pointers lifetimes are correctly managed. * * Return: The pointer associated with this ID. */ void *idr_find(const struct idr *idr, unsigned long id) { return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base); } EXPORT_SYMBOL_GPL(idr_find); /** |
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* idr_for_each() - Iterate through all stored pointers. * @idr: IDR handle. * @fn: Function to be called for each pointer. * @data: Data passed to callback function. |
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* |
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* The callback function will be called for each entry in @idr, passing |
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* the ID, the entry and @data. |
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* |
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* If @fn returns anything other than %0, the iteration stops and that * value is returned from this function. |
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* |
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* idr_for_each() can be called concurrently with idr_alloc() and * idr_remove() if protected by RCU. Newly added entries may not be * seen and deleted entries may be seen, but adding and removing entries * will not cause other entries to be skipped, nor spurious ones to be seen. |
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*/ |
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int idr_for_each(const struct idr *idr, int (*fn)(int id, void *p, void *data), void *data) |
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{ |
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struct radix_tree_iter iter; |
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void __rcu **slot; |
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int base = idr->idr_base; |
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radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) { |
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int ret; |
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unsigned long id = iter.index + base; |
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if (WARN_ON_ONCE(id > INT_MAX)) |
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break; |
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ret = fn(id, rcu_dereference_raw(*slot), data); |
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if (ret) return ret; |
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} |
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return 0; |
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} EXPORT_SYMBOL(idr_for_each); /** |
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* idr_get_next_ul() - Find next populated entry. |
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* @idr: IDR handle. * @nextid: Pointer to an ID. |
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* * Returns the next populated entry in the tree with an ID greater than * or equal to the value pointed to by @nextid. On exit, @nextid is updated * to the ID of the found value. To use in a loop, the value pointed to by * nextid must be incremented by the user. |
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*/ |
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void *idr_get_next_ul(struct idr *idr, unsigned long *nextid) |
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{ |
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struct radix_tree_iter iter; |
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void __rcu **slot; |
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void *entry = NULL; |
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unsigned long base = idr->idr_base; unsigned long id = *nextid; |
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id = (id < base) ? 0 : id - base; |
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radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, id) { entry = rcu_dereference_raw(*slot); if (!entry) continue; if (!xa_is_internal(entry)) break; if (slot != &idr->idr_rt.xa_head && !xa_is_retry(entry)) break; slot = radix_tree_iter_retry(&iter); } |
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if (!slot) |
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return NULL; |
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*nextid = iter.index + base; |
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return entry; |
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} |
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EXPORT_SYMBOL(idr_get_next_ul); |
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/** |
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* idr_get_next() - Find next populated entry. |
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* @idr: IDR handle. * @nextid: Pointer to an ID. * * Returns the next populated entry in the tree with an ID greater than * or equal to the value pointed to by @nextid. On exit, @nextid is updated * to the ID of the found value. To use in a loop, the value pointed to by * nextid must be incremented by the user. */ |
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void *idr_get_next(struct idr *idr, int *nextid) |
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{ |
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unsigned long id = *nextid; |
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void *entry = idr_get_next_ul(idr, &id); |
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if (WARN_ON_ONCE(id > INT_MAX)) |
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return NULL; |
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*nextid = id; return entry; |
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} |
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EXPORT_SYMBOL(idr_get_next); |
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/** |
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* idr_replace() - replace pointer for given ID. * @idr: IDR handle. * @ptr: New pointer to associate with the ID. * @id: ID to change. |
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* |
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* Replace the pointer registered with an ID and return the old value. * This function can be called under the RCU read lock concurrently with * idr_alloc() and idr_remove() (as long as the ID being removed is not * the one being replaced!). |
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* |
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* Returns: the old value on success. %-ENOENT indicates that @id was not |
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* found. %-EINVAL indicates that @ptr was not valid. |
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*/ |
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void *idr_replace(struct idr *idr, void *ptr, unsigned long id) |
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{ |
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struct radix_tree_node *node; |
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void __rcu **slot = NULL; |
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void *entry; |
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id -= idr->idr_base; |
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entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot); if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE)) |
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return ERR_PTR(-ENOENT); |
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__radix_tree_replace(&idr->idr_rt, node, slot, ptr); |
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return entry; |
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} |
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EXPORT_SYMBOL(idr_replace); |
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/** * DOC: IDA description |
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* |
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* The IDA is an ID allocator which does not provide the ability to * associate an ID with a pointer. As such, it only needs to store one * bit per ID, and so is more space efficient than an IDR. To use an IDA, * define it using DEFINE_IDA() (or embed a &struct ida in a data structure, * then initialise it using ida_init()). To allocate a new ID, call |
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* ida_alloc(), ida_alloc_min(), ida_alloc_max() or ida_alloc_range(). * To free an ID, call ida_free(). |
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* |
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* ida_destroy() can be used to dispose of an IDA without needing to * free the individual IDs in it. You can use ida_is_empty() to find * out whether the IDA has any IDs currently allocated. |
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* |
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* The IDA handles its own locking. It is safe to call any of the IDA * functions without synchronisation in your code. * |
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* IDs are currently limited to the range [0-INT_MAX]. If this is an awkward * limitation, it should be quite straightforward to raise the maximum. |
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*/ |
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/* * Developer's notes: * |
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* The IDA uses the functionality provided by the XArray to store bitmaps in * each entry. The XA_FREE_MARK is only cleared when all bits in the bitmap * have been set. |
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* |
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* I considered telling the XArray that each slot is an order-10 node * and indexing by bit number, but the XArray can't allow a single multi-index * entry in the head, which would significantly increase memory consumption * for the IDA. So instead we divide the index by the number of bits in the * leaf bitmap before doing a radix tree lookup. |
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* * As an optimisation, if there are only a few low bits set in any given |
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* leaf, instead of allocating a 128-byte bitmap, we store the bits |
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* as a value entry. Value entries never have the XA_FREE_MARK cleared * because we can always convert them into a bitmap entry. * * It would be possible to optimise further; once we've run out of a * single 128-byte bitmap, we currently switch to a 576-byte node, put * the 128-byte bitmap in the first entry and then start allocating extra * 128-byte entries. We could instead use the 512 bytes of the node's * data as a bitmap before moving to that scheme. I do not believe this * is a worthwhile optimisation; Rasmus Villemoes surveyed the current * users of the IDA and almost none of them use more than 1024 entries. * Those that do use more than the 8192 IDs that the 512 bytes would * provide. * * The IDA always uses a lock to alloc/free. If we add a 'test_bit' |
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* equivalent, it will still need locking. Going to RCU lookup would require * using RCU to free bitmaps, and that's not trivial without embedding an * RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte * bitmap, which is excessive. */ |
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/** * ida_alloc_range() - Allocate an unused ID. * @ida: IDA handle. * @min: Lowest ID to allocate. * @max: Highest ID to allocate. * @gfp: Memory allocation flags. * * Allocate an ID between @min and @max, inclusive. The allocated ID will * not exceed %INT_MAX, even if @max is larger. * |
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* Context: Any context. It is safe to call this function without * locking in your code. |
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* Return: The allocated ID, or %-ENOMEM if memory could not be allocated, * or %-ENOSPC if there are no free IDs. */ int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max, gfp_t gfp) |
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{ |
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XA_STATE(xas, &ida->xa, min / IDA_BITMAP_BITS); unsigned bit = min % IDA_BITMAP_BITS; unsigned long flags; struct ida_bitmap *bitmap, *alloc = NULL; if ((int)min < 0) return -ENOSPC; if ((int)max < 0) max = INT_MAX; retry: xas_lock_irqsave(&xas, flags); next: bitmap = xas_find_marked(&xas, max / IDA_BITMAP_BITS, XA_FREE_MARK); if (xas.xa_index > min / IDA_BITMAP_BITS) bit = 0; if (xas.xa_index * IDA_BITMAP_BITS + bit > max) goto nospc; if (xa_is_value(bitmap)) { unsigned long tmp = xa_to_value(bitmap); if (bit < BITS_PER_XA_VALUE) { bit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE, bit); if (xas.xa_index * IDA_BITMAP_BITS + bit > max) goto nospc; if (bit < BITS_PER_XA_VALUE) { tmp |= 1UL << bit; xas_store(&xas, xa_mk_value(tmp)); goto out; |
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} } |
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bitmap = alloc; if (!bitmap) bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT); if (!bitmap) goto alloc; bitmap->bitmap[0] = tmp; xas_store(&xas, bitmap); if (xas_error(&xas)) { bitmap->bitmap[0] = 0; goto out; |
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} |
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} |
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if (bitmap) { bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit); if (xas.xa_index * IDA_BITMAP_BITS + bit > max) goto nospc; if (bit == IDA_BITMAP_BITS) goto next; |
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__set_bit(bit, bitmap->bitmap); if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS)) xas_clear_mark(&xas, XA_FREE_MARK); } else { if (bit < BITS_PER_XA_VALUE) { bitmap = xa_mk_value(1UL << bit); |
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} else { |
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bitmap = alloc; if (!bitmap) bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT); if (!bitmap) goto alloc; __set_bit(bit, bitmap->bitmap); |
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} |
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xas_store(&xas, bitmap); } out: xas_unlock_irqrestore(&xas, flags); if (xas_nomem(&xas, gfp)) { xas.xa_index = min / IDA_BITMAP_BITS; bit = min % IDA_BITMAP_BITS; goto retry; |
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} |
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if (bitmap != alloc) kfree(alloc); if (xas_error(&xas)) return xas_error(&xas); return xas.xa_index * IDA_BITMAP_BITS + bit; alloc: xas_unlock_irqrestore(&xas, flags); alloc = kzalloc(sizeof(*bitmap), gfp); if (!alloc) return -ENOMEM; xas_set(&xas, min / IDA_BITMAP_BITS); bit = min % IDA_BITMAP_BITS; goto retry; nospc: xas_unlock_irqrestore(&xas, flags); |
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kfree(alloc); |
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return -ENOSPC; |
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} |
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EXPORT_SYMBOL(ida_alloc_range); |
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/** * ida_free() - Release an allocated ID. * @ida: IDA handle. * @id: Previously allocated ID. * |
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* Context: Any context. It is safe to call this function without * locking in your code. |
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*/ void ida_free(struct ida *ida, unsigned int id) |
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{ |
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485 486 |
XA_STATE(xas, &ida->xa, id / IDA_BITMAP_BITS); unsigned bit = id % IDA_BITMAP_BITS; |
72dba584b
|
487 |
struct ida_bitmap *bitmap; |
f32f004cd
|
488 |
unsigned long flags; |
72dba584b
|
489 |
|
f32f004cd
|
490 491 492 493 |
BUG_ON((int)id < 0); xas_lock_irqsave(&xas, flags); bitmap = xas_load(&xas); |
8f9f665a7
|
494 |
|
3159f943a
|
495 |
if (xa_is_value(bitmap)) { |
f32f004cd
|
496 497 498 499 |
unsigned long v = xa_to_value(bitmap); if (bit >= BITS_PER_XA_VALUE) goto err; if (!(v & (1UL << bit))) |
d37cacc5a
|
500 |
goto err; |
f32f004cd
|
501 502 503 504 |
v &= ~(1UL << bit); if (!v) goto delete; xas_store(&xas, xa_mk_value(v)); |
d37cacc5a
|
505 |
} else { |
f32f004cd
|
506 507 508 509 510 511 512 513 514 |
if (!test_bit(bit, bitmap->bitmap)) goto err; __clear_bit(bit, bitmap->bitmap); xas_set_mark(&xas, XA_FREE_MARK); if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) { kfree(bitmap); delete: xas_store(&xas, NULL); } |
72dba584b
|
515 |
} |
f32f004cd
|
516 |
xas_unlock_irqrestore(&xas, flags); |
72dba584b
|
517 |
return; |
72dba584b
|
518 |
err: |
f32f004cd
|
519 |
xas_unlock_irqrestore(&xas, flags); |
b03f8e43c
|
520 521 |
WARN(1, "ida_free called for id=%d which is not allocated. ", id); |
72dba584b
|
522 |
} |
f32f004cd
|
523 |
EXPORT_SYMBOL(ida_free); |
72dba584b
|
524 525 |
/** |
50d97d507
|
526 527 528 529 530 531 532 |
* ida_destroy() - Free all IDs. * @ida: IDA handle. * * Calling this function frees all IDs and releases all resources used * by an IDA. When this call returns, the IDA is empty and can be reused * or freed. If the IDA is already empty, there is no need to call this * function. |
0a835c4f0
|
533 |
* |
3b6742618
|
534 535 |
* Context: Any context. It is safe to call this function without * locking in your code. |
72dba584b
|
536 537 538 |
*/ void ida_destroy(struct ida *ida) { |
f32f004cd
|
539 540 |
XA_STATE(xas, &ida->xa, 0); struct ida_bitmap *bitmap; |
50d97d507
|
541 |
unsigned long flags; |
0a835c4f0
|
542 |
|
f32f004cd
|
543 544 |
xas_lock_irqsave(&xas, flags); xas_for_each(&xas, bitmap, ULONG_MAX) { |
3159f943a
|
545 |
if (!xa_is_value(bitmap)) |
d37cacc5a
|
546 |
kfree(bitmap); |
f32f004cd
|
547 |
xas_store(&xas, NULL); |
0a835c4f0
|
548 |
} |
f32f004cd
|
549 |
xas_unlock_irqrestore(&xas, flags); |
72dba584b
|
550 551 |
} EXPORT_SYMBOL(ida_destroy); |
f32f004cd
|
552 553 554 |
#ifndef __KERNEL__ extern void xa_dump_index(unsigned long index, unsigned int shift); #define IDA_CHUNK_SHIFT ilog2(IDA_BITMAP_BITS) |
88eca0207
|
555 |
|
f32f004cd
|
556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 |
static void ida_dump_entry(void *entry, unsigned long index) { unsigned long i; if (!entry) return; if (xa_is_node(entry)) { struct xa_node *node = xa_to_node(entry); unsigned int shift = node->shift + IDA_CHUNK_SHIFT + XA_CHUNK_SHIFT; xa_dump_index(index * IDA_BITMAP_BITS, shift); xa_dump_node(node); for (i = 0; i < XA_CHUNK_SIZE; i++) ida_dump_entry(node->slots[i], index | (i << node->shift)); } else if (xa_is_value(entry)) { xa_dump_index(index * IDA_BITMAP_BITS, ilog2(BITS_PER_LONG)); pr_cont("value: data %lx [%px] ", xa_to_value(entry), entry); } else { struct ida_bitmap *bitmap = entry; |
88eca0207
|
579 |
|
f32f004cd
|
580 581 582 583 584 585 |
xa_dump_index(index * IDA_BITMAP_BITS, IDA_CHUNK_SHIFT); pr_cont("bitmap: %p data", bitmap); for (i = 0; i < IDA_BITMAP_LONGS; i++) pr_cont(" %lx", bitmap->bitmap[i]); pr_cont(" "); |
5ade60dda
|
586 |
} |
88eca0207
|
587 |
} |
88eca0207
|
588 |
|
f32f004cd
|
589 |
static void ida_dump(struct ida *ida) |
88eca0207
|
590 |
{ |
f32f004cd
|
591 592 593 594 595 |
struct xarray *xa = &ida->xa; pr_debug("ida: %p node %p free %d ", ida, xa->xa_head, xa->xa_flags >> ROOT_TAG_SHIFT); ida_dump_entry(xa->xa_head, 0); |
88eca0207
|
596 |
} |
f32f004cd
|
597 |
#endif |