[PATCH 2/2] Remove percpu_ida

[Matthew Wilcox <willy@infradead.org>]

From: Matthew Wilcox <mawilcox@microsoft.com>

With its one user gone, remove the library code.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 include/linux/percpu_ida.h |  83 --------
 lib/Makefile               |   2 +-
 lib/percpu_ida.c           | 391 -------------------------------------
 3 files changed, 1 insertion(+), 475 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 ce20696d5a92..7626dece1d27 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -39,7 +39,7 @@ 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 6016f1deb1f5..000000000000
--- a/lib/percpu_ida.c
+++ /dev/null
@@ -1,391 +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));
-}
-
-static inline unsigned alloc_local_tag(struct percpu_ida_cpu *tags)
-{
-	int tag = -ENOSPC;
-
-	spin_lock(&tags->lock);
-	if (tags->nr_free)
-		tag = tags->freelist[--tags->nr_free];
-	spin_unlock(&tags->lock);
-
-	return tag;
-}
-
-/**
- * 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;
-
-	local_irq_save(flags);
-	tags = this_cpu_ptr(pool->tag_cpu);
-
-	/* Fastpath */
-	tag = alloc_local_tag(tags);
-	if (likely(tag >= 0)) {
-		local_irq_restore(flags);
-		return tag;
-	}
-
-	while (1) {
-		spin_lock(&pool->lock);
-
-		/*
-		 * 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(&pool->lock);
-		local_irq_restore(flags);
-
-		if (tag >= 0 || state == TASK_RUNNING)
-			break;
-
-		if (signal_pending_state(state, current)) {
-			tag = -ERESTARTSYS;
-			break;
-		}
-
-		schedule();
-
-		local_irq_save(flags);
-		tags = this_cpu_ptr(pool->tag_cpu);
-	}
-	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);
-
-	local_irq_save(flags);
-	tags = this_cpu_ptr(pool->tag_cpu);
-
-	spin_lock(&tags->lock);
-	tags->freelist[tags->nr_free++] = tag;
-
-	nr_free = tags->nr_free;
-	spin_unlock(&tags->lock);
-
-	if (nr_free == 1) {
-		cpumask_set_cpu(smp_processor_id(),
-				&pool->cpus_have_tags);
-		wake_up(&pool->wait);
-	}
-
-	if (nr_free == pool->percpu_max_size) {
-		spin_lock(&pool->lock);
-
-		/*
-		 * Global lock held and irqs disabled, don't need percpu
-		 * 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(&pool->lock);
-	}
-
-	local_irq_restore(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;
-
-	local_irq_save(flags);
-	for_each_possible_cpu(cpu) {
-		remote = per_cpu_ptr(pool->tag_cpu, cpu);
-		spin_lock(&remote->lock);
-		for (i = 0; i < remote->nr_free; i++) {
-			err = fn(remote->freelist[i], data);
-			if (err)
-				break;
-		}
-		spin_unlock(&remote->lock);
-		if (err)
-			goto out;
-	}
-
-	spin_lock(&pool->lock);
-	for (i = 0; i < pool->nr_free; i++) {
-		err = fn(pool->freelist[i], data);
-		if (err)
-			break;
-	}
-	spin_unlock(&pool->lock);
-out:
-	local_irq_restore(flags);
-	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);
-- 
2.17.0