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    Subject[PATCH 3/3] Remove percpu_ida
    Date
    With its one user gone, remove the library code.

    Signed-off-by: Matthew Wilcox <willy@infradead.org>
    ---
    include/linux/percpu_ida.h | 83 ---------
    lib/Makefile | 2 +-
    lib/percpu_ida.c | 370 -------------------------------------
    3 files changed, 1 insertion(+), 454 deletions(-)
    delete mode 100644 include/linux/percpu_ida.h
    delete mode 100644 lib/percpu_ida.c

    diff --git a/include/linux/percpu_ida.h b/include/linux/percpu_ida.h
    deleted file mode 100644
    index 07d78e4653bc..000000000000
    --- a/include/linux/percpu_ida.h
    +++ /dev/null
    @@ -1,83 +0,0 @@
    -/* SPDX-License-Identifier: GPL-2.0 */
    -#ifndef __PERCPU_IDA_H__
    -#define __PERCPU_IDA_H__
    -
    -#include <linux/types.h>
    -#include <linux/bitops.h>
    -#include <linux/init.h>
    -#include <linux/sched.h>
    -#include <linux/spinlock_types.h>
    -#include <linux/wait.h>
    -#include <linux/cpumask.h>
    -
    -struct percpu_ida_cpu;
    -
    -struct percpu_ida {
    - /*
    - * number of tags available to be allocated, as passed to
    - * percpu_ida_init()
    - */
    - unsigned nr_tags;
    - unsigned percpu_max_size;
    - unsigned percpu_batch_size;
    -
    - struct percpu_ida_cpu __percpu *tag_cpu;
    -
    - /*
    - * Bitmap of cpus that (may) have tags on their percpu freelists:
    - * steal_tags() uses this to decide when to steal tags, and which cpus
    - * to try stealing from.
    - *
    - * It's ok for a freelist to be empty when its bit is set - steal_tags()
    - * will just keep looking - but the bitmap _must_ be set whenever a
    - * percpu freelist does have tags.
    - */
    - cpumask_t cpus_have_tags;
    -
    - struct {
    - spinlock_t lock;
    - /*
    - * When we go to steal tags from another cpu (see steal_tags()),
    - * we want to pick a cpu at random. Cycling through them every
    - * time we steal is a bit easier and more or less equivalent:
    - */
    - unsigned cpu_last_stolen;
    -
    - /* For sleeping on allocation failure */
    - wait_queue_head_t wait;
    -
    - /*
    - * Global freelist - it's a stack where nr_free points to the
    - * top
    - */
    - unsigned nr_free;
    - unsigned *freelist;
    - } ____cacheline_aligned_in_smp;
    -};
    -
    -/*
    - * Number of tags we move between the percpu freelist and the global freelist at
    - * a time
    - */
    -#define IDA_DEFAULT_PCPU_BATCH_MOVE 32U
    -/* Max size of percpu freelist, */
    -#define IDA_DEFAULT_PCPU_SIZE ((IDA_DEFAULT_PCPU_BATCH_MOVE * 3) / 2)
    -
    -int percpu_ida_alloc(struct percpu_ida *pool, int state);
    -void percpu_ida_free(struct percpu_ida *pool, unsigned tag);
    -
    -void percpu_ida_destroy(struct percpu_ida *pool);
    -int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
    - unsigned long max_size, unsigned long batch_size);
    -static inline int percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags)
    -{
    - return __percpu_ida_init(pool, nr_tags, IDA_DEFAULT_PCPU_SIZE,
    - IDA_DEFAULT_PCPU_BATCH_MOVE);
    -}
    -
    -typedef int (*percpu_ida_cb)(unsigned, void *);
    -int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
    - void *data);
    -
    -unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu);
    -#endif /* __PERCPU_IDA_H__ */
    diff --git a/lib/Makefile b/lib/Makefile
    index 84c6dcb31fbb..f4722a7fa62c 100644
    --- a/lib/Makefile
    +++ b/lib/Makefile
    @@ -40,7 +40,7 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \
    bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \
    gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
    bsearch.o find_bit.o llist.o memweight.o kfifo.o \
    - percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \
    + percpu-refcount.o rhashtable.o reciprocal_div.o \
    once.o refcount.o usercopy.o errseq.o bucket_locks.o
    obj-$(CONFIG_STRING_SELFTEST) += test_string.o
    obj-y += string_helpers.o
    diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c
    deleted file mode 100644
    index 9bbd9c5d375a..000000000000
    --- a/lib/percpu_ida.c
    +++ /dev/null
    @@ -1,370 +0,0 @@
    -/*
    - * Percpu IDA library
    - *
    - * Copyright (C) 2013 Datera, Inc. Kent Overstreet
    - *
    - * This program is free software; you can redistribute it and/or
    - * modify it under the terms of the GNU General Public License as
    - * published by the Free Software Foundation; either version 2, or (at
    - * your option) any later version.
    - *
    - * This program is distributed in the hope that it will be useful, but
    - * WITHOUT ANY WARRANTY; without even the implied warranty of
    - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    - * General Public License for more details.
    - */
    -
    -#include <linux/mm.h>
    -#include <linux/bitmap.h>
    -#include <linux/bitops.h>
    -#include <linux/bug.h>
    -#include <linux/err.h>
    -#include <linux/export.h>
    -#include <linux/init.h>
    -#include <linux/kernel.h>
    -#include <linux/percpu.h>
    -#include <linux/sched/signal.h>
    -#include <linux/string.h>
    -#include <linux/spinlock.h>
    -#include <linux/percpu_ida.h>
    -
    -struct percpu_ida_cpu {
    - /*
    - * Even though this is percpu, we need a lock for tag stealing by remote
    - * CPUs:
    - */
    - spinlock_t lock;
    -
    - /* nr_free/freelist form a stack of free IDs */
    - unsigned nr_free;
    - unsigned freelist[];
    -};
    -
    -static inline void move_tags(unsigned *dst, unsigned *dst_nr,
    - unsigned *src, unsigned *src_nr,
    - unsigned nr)
    -{
    - *src_nr -= nr;
    - memcpy(dst + *dst_nr, src + *src_nr, sizeof(unsigned) * nr);
    - *dst_nr += nr;
    -}
    -
    -/*
    - * Try to steal tags from a remote cpu's percpu freelist.
    - *
    - * We first check how many percpu freelists have tags
    - *
    - * Then we iterate through the cpus until we find some tags - we don't attempt
    - * to find the "best" cpu to steal from, to keep cacheline bouncing to a
    - * minimum.
    - */
    -static inline void steal_tags(struct percpu_ida *pool,
    - struct percpu_ida_cpu *tags)
    -{
    - unsigned cpus_have_tags, cpu = pool->cpu_last_stolen;
    - struct percpu_ida_cpu *remote;
    -
    - for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags);
    - cpus_have_tags; cpus_have_tags--) {
    - cpu = cpumask_next(cpu, &pool->cpus_have_tags);
    -
    - if (cpu >= nr_cpu_ids) {
    - cpu = cpumask_first(&pool->cpus_have_tags);
    - if (cpu >= nr_cpu_ids)
    - BUG();
    - }
    -
    - pool->cpu_last_stolen = cpu;
    - remote = per_cpu_ptr(pool->tag_cpu, cpu);
    -
    - cpumask_clear_cpu(cpu, &pool->cpus_have_tags);
    -
    - if (remote == tags)
    - continue;
    -
    - spin_lock(&remote->lock);
    -
    - if (remote->nr_free) {
    - memcpy(tags->freelist,
    - remote->freelist,
    - sizeof(unsigned) * remote->nr_free);
    -
    - tags->nr_free = remote->nr_free;
    - remote->nr_free = 0;
    - }
    -
    - spin_unlock(&remote->lock);
    -
    - if (tags->nr_free)
    - break;
    - }
    -}
    -
    -/*
    - * Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them onto
    - * our percpu freelist:
    - */
    -static inline void alloc_global_tags(struct percpu_ida *pool,
    - struct percpu_ida_cpu *tags)
    -{
    - move_tags(tags->freelist, &tags->nr_free,
    - pool->freelist, &pool->nr_free,
    - min(pool->nr_free, pool->percpu_batch_size));
    -}
    -
    -/**
    - * percpu_ida_alloc - allocate a tag
    - * @pool: pool to allocate from
    - * @state: task state for prepare_to_wait
    - *
    - * Returns a tag - an integer in the range [0..nr_tags) (passed to
    - * tag_pool_init()), or otherwise -ENOSPC on allocation failure.
    - *
    - * Safe to be called from interrupt context (assuming it isn't passed
    - * TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, of course).
    - *
    - * @gfp indicates whether or not to wait until a free id is available (it's not
    - * used for internal memory allocations); thus if passed __GFP_RECLAIM we may sleep
    - * however long it takes until another thread frees an id (same semantics as a
    - * mempool).
    - *
    - * Will not fail if passed TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE.
    - */
    -int percpu_ida_alloc(struct percpu_ida *pool, int state)
    -{
    - DEFINE_WAIT(wait);
    - struct percpu_ida_cpu *tags;
    - unsigned long flags;
    - int tag = -ENOSPC;
    -
    - tags = raw_cpu_ptr(pool->tag_cpu);
    - spin_lock_irqsave(&tags->lock, flags);
    -
    - /* Fastpath */
    - if (likely(tags->nr_free >= 0)) {
    - tag = tags->freelist[--tags->nr_free];
    - spin_unlock_irqrestore(&tags->lock, flags);
    - return tag;
    - }
    - spin_unlock_irqrestore(&tags->lock, flags);
    -
    - while (1) {
    - spin_lock_irqsave(&pool->lock, flags);
    - tags = this_cpu_ptr(pool->tag_cpu);
    -
    - /*
    - * prepare_to_wait() must come before steal_tags(), in case
    - * percpu_ida_free() on another cpu flips a bit in
    - * cpus_have_tags
    - *
    - * global lock held and irqs disabled, don't need percpu lock
    - */
    - if (state != TASK_RUNNING)
    - prepare_to_wait(&pool->wait, &wait, state);
    -
    - if (!tags->nr_free)
    - alloc_global_tags(pool, tags);
    - if (!tags->nr_free)
    - steal_tags(pool, tags);
    -
    - if (tags->nr_free) {
    - tag = tags->freelist[--tags->nr_free];
    - if (tags->nr_free)
    - cpumask_set_cpu(smp_processor_id(),
    - &pool->cpus_have_tags);
    - }
    -
    - spin_unlock_irqrestore(&pool->lock, flags);
    -
    - if (tag >= 0 || state == TASK_RUNNING)
    - break;
    -
    - if (signal_pending_state(state, current)) {
    - tag = -ERESTARTSYS;
    - break;
    - }
    -
    - schedule();
    - }
    - if (state != TASK_RUNNING)
    - finish_wait(&pool->wait, &wait);
    -
    - return tag;
    -}
    -EXPORT_SYMBOL_GPL(percpu_ida_alloc);
    -
    -/**
    - * percpu_ida_free - free a tag
    - * @pool: pool @tag was allocated from
    - * @tag: a tag previously allocated with percpu_ida_alloc()
    - *
    - * Safe to be called from interrupt context.
    - */
    -void percpu_ida_free(struct percpu_ida *pool, unsigned tag)
    -{
    - struct percpu_ida_cpu *tags;
    - unsigned long flags;
    - unsigned nr_free;
    -
    - BUG_ON(tag >= pool->nr_tags);
    -
    - tags = raw_cpu_ptr(pool->tag_cpu);
    -
    - spin_lock_irqsave(&tags->lock, flags);
    - tags->freelist[tags->nr_free++] = tag;
    -
    - nr_free = tags->nr_free;
    -
    - if (nr_free == 1) {
    - cpumask_set_cpu(smp_processor_id(),
    - &pool->cpus_have_tags);
    - wake_up(&pool->wait);
    - }
    - spin_unlock_irqrestore(&tags->lock, flags);
    -
    - if (nr_free == pool->percpu_max_size) {
    - spin_lock_irqsave(&pool->lock, flags);
    - spin_lock(&tags->lock);
    -
    - if (tags->nr_free == pool->percpu_max_size) {
    - move_tags(pool->freelist, &pool->nr_free,
    - tags->freelist, &tags->nr_free,
    - pool->percpu_batch_size);
    -
    - wake_up(&pool->wait);
    - }
    - spin_unlock(&tags->lock);
    - spin_unlock_irqrestore(&pool->lock, flags);
    - }
    -}
    -EXPORT_SYMBOL_GPL(percpu_ida_free);
    -
    -/**
    - * percpu_ida_destroy - release a tag pool's resources
    - * @pool: pool to free
    - *
    - * Frees the resources allocated by percpu_ida_init().
    - */
    -void percpu_ida_destroy(struct percpu_ida *pool)
    -{
    - free_percpu(pool->tag_cpu);
    - free_pages((unsigned long) pool->freelist,
    - get_order(pool->nr_tags * sizeof(unsigned)));
    -}
    -EXPORT_SYMBOL_GPL(percpu_ida_destroy);
    -
    -/**
    - * percpu_ida_init - initialize a percpu tag pool
    - * @pool: pool to initialize
    - * @nr_tags: number of tags that will be available for allocation
    - *
    - * Initializes @pool so that it can be used to allocate tags - integers in the
    - * range [0, nr_tags). Typically, they'll be used by driver code to refer to a
    - * preallocated array of tag structures.
    - *
    - * Allocation is percpu, but sharding is limited by nr_tags - for best
    - * performance, the workload should not span more cpus than nr_tags / 128.
    - */
    -int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
    - unsigned long max_size, unsigned long batch_size)
    -{
    - unsigned i, cpu, order;
    -
    - memset(pool, 0, sizeof(*pool));
    -
    - init_waitqueue_head(&pool->wait);
    - spin_lock_init(&pool->lock);
    - pool->nr_tags = nr_tags;
    - pool->percpu_max_size = max_size;
    - pool->percpu_batch_size = batch_size;
    -
    - /* Guard against overflow */
    - if (nr_tags > (unsigned) INT_MAX + 1) {
    - pr_err("percpu_ida_init(): nr_tags too large\n");
    - return -EINVAL;
    - }
    -
    - order = get_order(nr_tags * sizeof(unsigned));
    - pool->freelist = (void *) __get_free_pages(GFP_KERNEL, order);
    - if (!pool->freelist)
    - return -ENOMEM;
    -
    - for (i = 0; i < nr_tags; i++)
    - pool->freelist[i] = i;
    -
    - pool->nr_free = nr_tags;
    -
    - pool->tag_cpu = __alloc_percpu(sizeof(struct percpu_ida_cpu) +
    - pool->percpu_max_size * sizeof(unsigned),
    - sizeof(unsigned));
    - if (!pool->tag_cpu)
    - goto err;
    -
    - for_each_possible_cpu(cpu)
    - spin_lock_init(&per_cpu_ptr(pool->tag_cpu, cpu)->lock);
    -
    - return 0;
    -err:
    - percpu_ida_destroy(pool);
    - return -ENOMEM;
    -}
    -EXPORT_SYMBOL_GPL(__percpu_ida_init);
    -
    -/**
    - * percpu_ida_for_each_free - iterate free ids of a pool
    - * @pool: pool to iterate
    - * @fn: interate callback function
    - * @data: parameter for @fn
    - *
    - * Note, this doesn't guarantee to iterate all free ids restrictly. Some free
    - * ids might be missed, some might be iterated duplicated, and some might
    - * be iterated and not free soon.
    - */
    -int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
    - void *data)
    -{
    - unsigned long flags;
    - struct percpu_ida_cpu *remote;
    - unsigned cpu, i, err = 0;
    -
    - for_each_possible_cpu(cpu) {
    - remote = per_cpu_ptr(pool->tag_cpu, cpu);
    - spin_lock_irqsave(&remote->lock, flags);
    - for (i = 0; i < remote->nr_free; i++) {
    - err = fn(remote->freelist[i], data);
    - if (err)
    - break;
    - }
    - spin_unlock_irqrestore(&remote->lock, flags);
    - if (err)
    - goto out;
    - }
    -
    - spin_lock_irqsave(&pool->lock, flags);
    - for (i = 0; i < pool->nr_free; i++) {
    - err = fn(pool->freelist[i], data);
    - if (err)
    - break;
    - }
    - spin_unlock_irqrestore(&pool->lock, flags);
    -out:
    - return err;
    -}
    -EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);
    -
    -/**
    - * percpu_ida_free_tags - return free tags number of a specific cpu or global pool
    - * @pool: pool related
    - * @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
    - *
    - * Note: this just returns a snapshot of free tags number.
    - */
    -unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu)
    -{
    - struct percpu_ida_cpu *remote;
    - if (cpu == nr_cpu_ids)
    - return pool->nr_free;
    - remote = per_cpu_ptr(pool->tag_cpu, cpu);
    - return remote->nr_free;
    -}
    -EXPORT_SYMBOL_GPL(percpu_ida_free_tags);
    --
    2.17.1
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      Last update: 2018-06-12 21:08    [W:2.326 / U:0.132 seconds]
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