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578 lines
16 KiB
578 lines
16 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
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/* |
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* Fast and scalable bitmaps. |
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* |
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* Copyright (C) 2016 Facebook |
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* Copyright (C) 2013-2014 Jens Axboe |
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*/ |
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#ifndef __LINUX_SCALE_BITMAP_H |
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#define __LINUX_SCALE_BITMAP_H |
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#include <linux/kernel.h> |
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#include <linux/slab.h> |
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struct seq_file; |
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/** |
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* struct sbitmap_word - Word in a &struct sbitmap. |
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*/ |
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struct sbitmap_word { |
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/** |
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* @depth: Number of bits being used in @word/@cleared |
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*/ |
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unsigned long depth; |
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/** |
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* @word: word holding free bits |
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*/ |
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unsigned long word ____cacheline_aligned_in_smp; |
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/** |
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* @cleared: word holding cleared bits |
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*/ |
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unsigned long cleared ____cacheline_aligned_in_smp; |
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} ____cacheline_aligned_in_smp; |
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/** |
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* struct sbitmap - Scalable bitmap. |
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* |
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* A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This |
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* trades off higher memory usage for better scalability. |
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*/ |
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struct sbitmap { |
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/** |
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* @depth: Number of bits used in the whole bitmap. |
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*/ |
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unsigned int depth; |
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/** |
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* @shift: log2(number of bits used per word) |
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*/ |
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unsigned int shift; |
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/** |
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* @map_nr: Number of words (cachelines) being used for the bitmap. |
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*/ |
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unsigned int map_nr; |
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/** |
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* @map: Allocated bitmap. |
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*/ |
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struct sbitmap_word *map; |
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}; |
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#define SBQ_WAIT_QUEUES 8 |
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#define SBQ_WAKE_BATCH 8 |
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/** |
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* struct sbq_wait_state - Wait queue in a &struct sbitmap_queue. |
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*/ |
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struct sbq_wait_state { |
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/** |
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* @wait_cnt: Number of frees remaining before we wake up. |
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*/ |
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atomic_t wait_cnt; |
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/** |
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* @wait: Wait queue. |
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*/ |
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wait_queue_head_t wait; |
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} ____cacheline_aligned_in_smp; |
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/** |
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* struct sbitmap_queue - Scalable bitmap with the added ability to wait on free |
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* bits. |
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* |
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* A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to |
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* avoid contention on the wait queue spinlock. This ensures that we don't hit a |
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* scalability wall when we run out of free bits and have to start putting tasks |
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* to sleep. |
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*/ |
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struct sbitmap_queue { |
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/** |
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* @sb: Scalable bitmap. |
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*/ |
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struct sbitmap sb; |
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/* |
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* @alloc_hint: Cache of last successfully allocated or freed bit. |
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* |
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* This is per-cpu, which allows multiple users to stick to different |
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* cachelines until the map is exhausted. |
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*/ |
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unsigned int __percpu *alloc_hint; |
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/** |
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* @wake_batch: Number of bits which must be freed before we wake up any |
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* waiters. |
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*/ |
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unsigned int wake_batch; |
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/** |
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* @wake_index: Next wait queue in @ws to wake up. |
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*/ |
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atomic_t wake_index; |
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/** |
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* @ws: Wait queues. |
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*/ |
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struct sbq_wait_state *ws; |
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/* |
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* @ws_active: count of currently active ws waitqueues |
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*/ |
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atomic_t ws_active; |
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/** |
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* @round_robin: Allocate bits in strict round-robin order. |
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*/ |
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bool round_robin; |
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/** |
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* @min_shallow_depth: The minimum shallow depth which may be passed to |
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* sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow(). |
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*/ |
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unsigned int min_shallow_depth; |
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}; |
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/** |
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* sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node. |
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* @sb: Bitmap to initialize. |
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* @depth: Number of bits to allocate. |
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* @shift: Use 2^@shift bits per word in the bitmap; if a negative number if |
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* given, a good default is chosen. |
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* @flags: Allocation flags. |
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* @node: Memory node to allocate on. |
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* |
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* Return: Zero on success or negative errno on failure. |
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*/ |
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int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, |
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gfp_t flags, int node); |
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/** |
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* sbitmap_free() - Free memory used by a &struct sbitmap. |
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* @sb: Bitmap to free. |
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*/ |
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static inline void sbitmap_free(struct sbitmap *sb) |
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{ |
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kfree(sb->map); |
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sb->map = NULL; |
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} |
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/** |
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* sbitmap_resize() - Resize a &struct sbitmap. |
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* @sb: Bitmap to resize. |
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* @depth: New number of bits to resize to. |
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* |
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* Doesn't reallocate anything. It's up to the caller to ensure that the new |
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* depth doesn't exceed the depth that the sb was initialized with. |
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*/ |
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void sbitmap_resize(struct sbitmap *sb, unsigned int depth); |
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/** |
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* sbitmap_get() - Try to allocate a free bit from a &struct sbitmap. |
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* @sb: Bitmap to allocate from. |
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* @alloc_hint: Hint for where to start searching for a free bit. |
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* @round_robin: If true, be stricter about allocation order; always allocate |
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* starting from the last allocated bit. This is less efficient |
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* than the default behavior (false). |
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* |
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* This operation provides acquire barrier semantics if it succeeds. |
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* |
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* Return: Non-negative allocated bit number if successful, -1 otherwise. |
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*/ |
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int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin); |
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/** |
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* sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap, |
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* limiting the depth used from each word. |
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* @sb: Bitmap to allocate from. |
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* @alloc_hint: Hint for where to start searching for a free bit. |
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* @shallow_depth: The maximum number of bits to allocate from a single word. |
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* |
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* This rather specific operation allows for having multiple users with |
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* different allocation limits. E.g., there can be a high-priority class that |
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* uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow() |
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* with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority |
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* class can only allocate half of the total bits in the bitmap, preventing it |
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* from starving out the high-priority class. |
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* |
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* Return: Non-negative allocated bit number if successful, -1 otherwise. |
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*/ |
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int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint, |
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unsigned long shallow_depth); |
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/** |
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* sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap. |
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* @sb: Bitmap to check. |
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* |
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* Return: true if any bit in the bitmap is set, false otherwise. |
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*/ |
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bool sbitmap_any_bit_set(const struct sbitmap *sb); |
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#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift) |
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#define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U)) |
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typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *); |
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/** |
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* __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap. |
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* @start: Where to start the iteration. |
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* @sb: Bitmap to iterate over. |
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* @fn: Callback. Should return true to continue or false to break early. |
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* @data: Pointer to pass to callback. |
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* |
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* This is inline even though it's non-trivial so that the function calls to the |
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* callback will hopefully get optimized away. |
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*/ |
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static inline void __sbitmap_for_each_set(struct sbitmap *sb, |
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unsigned int start, |
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sb_for_each_fn fn, void *data) |
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{ |
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unsigned int index; |
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unsigned int nr; |
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unsigned int scanned = 0; |
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if (start >= sb->depth) |
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start = 0; |
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index = SB_NR_TO_INDEX(sb, start); |
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nr = SB_NR_TO_BIT(sb, start); |
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while (scanned < sb->depth) { |
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unsigned long word; |
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unsigned int depth = min_t(unsigned int, |
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sb->map[index].depth - nr, |
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sb->depth - scanned); |
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scanned += depth; |
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word = sb->map[index].word & ~sb->map[index].cleared; |
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if (!word) |
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goto next; |
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/* |
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* On the first iteration of the outer loop, we need to add the |
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* bit offset back to the size of the word for find_next_bit(). |
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* On all other iterations, nr is zero, so this is a noop. |
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*/ |
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depth += nr; |
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while (1) { |
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nr = find_next_bit(&word, depth, nr); |
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if (nr >= depth) |
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break; |
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if (!fn(sb, (index << sb->shift) + nr, data)) |
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return; |
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nr++; |
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} |
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next: |
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nr = 0; |
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if (++index >= sb->map_nr) |
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index = 0; |
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} |
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} |
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/** |
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* sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap. |
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* @sb: Bitmap to iterate over. |
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* @fn: Callback. Should return true to continue or false to break early. |
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* @data: Pointer to pass to callback. |
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*/ |
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static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn, |
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void *data) |
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{ |
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__sbitmap_for_each_set(sb, 0, fn, data); |
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} |
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static inline unsigned long *__sbitmap_word(struct sbitmap *sb, |
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unsigned int bitnr) |
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{ |
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return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word; |
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} |
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/* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */ |
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static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr) |
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{ |
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set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); |
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} |
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static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr) |
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{ |
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clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); |
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} |
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/* |
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* This one is special, since it doesn't actually clear the bit, rather it |
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* sets the corresponding bit in the ->cleared mask instead. Paired with |
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* the caller doing sbitmap_deferred_clear() if a given index is full, which |
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* will clear the previously freed entries in the corresponding ->word. |
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*/ |
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static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr) |
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{ |
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unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared; |
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set_bit(SB_NR_TO_BIT(sb, bitnr), addr); |
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} |
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static inline void sbitmap_clear_bit_unlock(struct sbitmap *sb, |
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unsigned int bitnr) |
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{ |
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clear_bit_unlock(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); |
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} |
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static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr) |
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{ |
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return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); |
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} |
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/** |
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* sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file. |
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* @sb: Bitmap to show. |
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* @m: struct seq_file to write to. |
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* |
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* This is intended for debugging. The format may change at any time. |
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*/ |
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void sbitmap_show(struct sbitmap *sb, struct seq_file *m); |
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/** |
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* sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct |
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* seq_file. |
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* @sb: Bitmap to show. |
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* @m: struct seq_file to write to. |
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* |
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* This is intended for debugging. The output isn't guaranteed to be internally |
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* consistent. |
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*/ |
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void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m); |
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/** |
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* sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific |
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* memory node. |
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* @sbq: Bitmap queue to initialize. |
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* @depth: See sbitmap_init_node(). |
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* @shift: See sbitmap_init_node(). |
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* @round_robin: See sbitmap_get(). |
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* @flags: Allocation flags. |
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* @node: Memory node to allocate on. |
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* |
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* Return: Zero on success or negative errno on failure. |
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*/ |
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int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, |
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int shift, bool round_robin, gfp_t flags, int node); |
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/** |
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* sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue. |
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* |
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* @sbq: Bitmap queue to free. |
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*/ |
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static inline void sbitmap_queue_free(struct sbitmap_queue *sbq) |
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{ |
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kfree(sbq->ws); |
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free_percpu(sbq->alloc_hint); |
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sbitmap_free(&sbq->sb); |
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} |
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/** |
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* sbitmap_queue_resize() - Resize a &struct sbitmap_queue. |
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* @sbq: Bitmap queue to resize. |
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* @depth: New number of bits to resize to. |
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* |
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* Like sbitmap_resize(), this doesn't reallocate anything. It has to do |
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* some extra work on the &struct sbitmap_queue, so it's not safe to just |
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* resize the underlying &struct sbitmap. |
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*/ |
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void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth); |
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/** |
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* __sbitmap_queue_get() - Try to allocate a free bit from a &struct |
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* sbitmap_queue with preemption already disabled. |
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* @sbq: Bitmap queue to allocate from. |
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* |
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* Return: Non-negative allocated bit number if successful, -1 otherwise. |
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*/ |
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int __sbitmap_queue_get(struct sbitmap_queue *sbq); |
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/** |
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* __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct |
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* sbitmap_queue, limiting the depth used from each word, with preemption |
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* already disabled. |
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* @sbq: Bitmap queue to allocate from. |
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* @shallow_depth: The maximum number of bits to allocate from a single word. |
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* See sbitmap_get_shallow(). |
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* |
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* If you call this, make sure to call sbitmap_queue_min_shallow_depth() after |
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* initializing @sbq. |
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* |
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* Return: Non-negative allocated bit number if successful, -1 otherwise. |
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*/ |
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int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq, |
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unsigned int shallow_depth); |
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/** |
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* sbitmap_queue_get() - Try to allocate a free bit from a &struct |
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* sbitmap_queue. |
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* @sbq: Bitmap queue to allocate from. |
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* @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to |
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* sbitmap_queue_clear()). |
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* |
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* Return: Non-negative allocated bit number if successful, -1 otherwise. |
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*/ |
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static inline int sbitmap_queue_get(struct sbitmap_queue *sbq, |
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unsigned int *cpu) |
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{ |
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int nr; |
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*cpu = get_cpu(); |
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nr = __sbitmap_queue_get(sbq); |
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put_cpu(); |
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return nr; |
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} |
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/** |
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* sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct |
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* sbitmap_queue, limiting the depth used from each word. |
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* @sbq: Bitmap queue to allocate from. |
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* @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to |
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* sbitmap_queue_clear()). |
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* @shallow_depth: The maximum number of bits to allocate from a single word. |
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* See sbitmap_get_shallow(). |
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* |
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* If you call this, make sure to call sbitmap_queue_min_shallow_depth() after |
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* initializing @sbq. |
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* |
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* Return: Non-negative allocated bit number if successful, -1 otherwise. |
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*/ |
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static inline int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq, |
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unsigned int *cpu, |
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unsigned int shallow_depth) |
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{ |
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int nr; |
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*cpu = get_cpu(); |
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nr = __sbitmap_queue_get_shallow(sbq, shallow_depth); |
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put_cpu(); |
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return nr; |
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} |
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/** |
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* sbitmap_queue_min_shallow_depth() - Inform a &struct sbitmap_queue of the |
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* minimum shallow depth that will be used. |
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* @sbq: Bitmap queue in question. |
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* @min_shallow_depth: The minimum shallow depth that will be passed to |
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* sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow(). |
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* |
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* sbitmap_queue_clear() batches wakeups as an optimization. The batch size |
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* depends on the depth of the bitmap. Since the shallow allocation functions |
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* effectively operate with a different depth, the shallow depth must be taken |
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* into account when calculating the batch size. This function must be called |
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* with the minimum shallow depth that will be used. Failure to do so can result |
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* in missed wakeups. |
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*/ |
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void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq, |
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unsigned int min_shallow_depth); |
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/** |
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* sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a |
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* &struct sbitmap_queue. |
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* @sbq: Bitmap to free from. |
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* @nr: Bit number to free. |
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* @cpu: CPU the bit was allocated on. |
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*/ |
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void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, |
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unsigned int cpu); |
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static inline int sbq_index_inc(int index) |
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{ |
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return (index + 1) & (SBQ_WAIT_QUEUES - 1); |
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} |
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static inline void sbq_index_atomic_inc(atomic_t *index) |
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{ |
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int old = atomic_read(index); |
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int new = sbq_index_inc(old); |
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atomic_cmpxchg(index, old, new); |
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} |
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/** |
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* sbq_wait_ptr() - Get the next wait queue to use for a &struct |
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* sbitmap_queue. |
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* @sbq: Bitmap queue to wait on. |
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* @wait_index: A counter per "user" of @sbq. |
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*/ |
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static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq, |
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atomic_t *wait_index) |
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{ |
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struct sbq_wait_state *ws; |
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ws = &sbq->ws[atomic_read(wait_index)]; |
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sbq_index_atomic_inc(wait_index); |
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return ws; |
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} |
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/** |
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* sbitmap_queue_wake_all() - Wake up everything waiting on a &struct |
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* sbitmap_queue. |
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* @sbq: Bitmap queue to wake up. |
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*/ |
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void sbitmap_queue_wake_all(struct sbitmap_queue *sbq); |
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/** |
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* sbitmap_queue_wake_up() - Wake up some of waiters in one waitqueue |
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* on a &struct sbitmap_queue. |
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* @sbq: Bitmap queue to wake up. |
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*/ |
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void sbitmap_queue_wake_up(struct sbitmap_queue *sbq); |
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/** |
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* sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct |
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* seq_file. |
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* @sbq: Bitmap queue to show. |
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* @m: struct seq_file to write to. |
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* |
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* This is intended for debugging. The format may change at any time. |
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*/ |
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void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m); |
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struct sbq_wait { |
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struct sbitmap_queue *sbq; /* if set, sbq_wait is accounted */ |
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struct wait_queue_entry wait; |
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}; |
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#define DEFINE_SBQ_WAIT(name) \ |
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struct sbq_wait name = { \ |
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.sbq = NULL, \ |
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.wait = { \ |
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.private = current, \ |
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.func = autoremove_wake_function, \ |
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.entry = LIST_HEAD_INIT((name).wait.entry), \ |
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} \ |
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} |
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/* |
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* Wrapper around prepare_to_wait_exclusive(), which maintains some extra |
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* internal state. |
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*/ |
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void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq, |
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struct sbq_wait_state *ws, |
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struct sbq_wait *sbq_wait, int state); |
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|
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/* |
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* Must be paired with sbitmap_prepare_to_wait(). |
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*/ |
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void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws, |
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struct sbq_wait *sbq_wait); |
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/* |
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* Wrapper around add_wait_queue(), which maintains some extra internal state |
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*/ |
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void sbitmap_add_wait_queue(struct sbitmap_queue *sbq, |
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struct sbq_wait_state *ws, |
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struct sbq_wait *sbq_wait); |
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/* |
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* Must be paired with sbitmap_add_wait_queue() |
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*/ |
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void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait); |
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#endif /* __LINUX_SCALE_BITMAP_H */
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