cregit-Linux how code gets into the kernel

Release 4.12 mm/percpu-km.c

Directory: mm
/*
 * mm/percpu-km.c - kernel memory based chunk allocation
 *
 * Copyright (C) 2010           SUSE Linux Products GmbH
 * Copyright (C) 2010           Tejun Heo <tj@kernel.org>
 *
 * This file is released under the GPLv2.
 *
 * Chunks are allocated as a contiguous kernel memory using gfp
 * allocation.  This is to be used on nommu architectures.
 *
 * To use percpu-km,
 *
 * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
 *
 * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined.  It's
 *   not compatible with PER_CPU_KM.  EMBED_FIRST_CHUNK should work
 *   fine.
 *
 * - NUMA is not supported.  When setting up the first chunk,
 *   @cpu_distance_fn should be NULL or report all CPUs to be nearer
 *   than or at LOCAL_DISTANCE.
 *
 * - It's best if the chunk size is power of two multiple of
 *   PAGE_SIZE.  Because each chunk is allocated as a contiguous
 *   kernel memory block using alloc_pages(), memory will be wasted if
 *   chunk size is not aligned.  percpu-km code will whine about it.
 */

#if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
#error "contiguous percpu allocation is incompatible with paged first chunk"
#endif

#include <linux/log2.h>


static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int page_start, int page_end) { return 0; }

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static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int page_start, int page_end) { /* nada */ }

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static struct pcpu_chunk *pcpu_create_chunk(void) { const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; struct pcpu_chunk *chunk; struct page *pages; int i; chunk = pcpu_alloc_chunk(); if (!chunk) return NULL; pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages)); if (!pages) { pcpu_free_chunk(chunk); return NULL; } for (i = 0; i < nr_pages; i++) pcpu_set_page_chunk(nth_page(pages, i), chunk); chunk->data = pages; chunk->base_addr = page_address(pages) - pcpu_group_offsets[0]; spin_lock_irq(&pcpu_lock); pcpu_chunk_populated(chunk, 0, nr_pages); spin_unlock_irq(&pcpu_lock); return chunk; }

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static void pcpu_destroy_chunk(struct pcpu_chunk *chunk) { const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; if (chunk && chunk->data) __free_pages(chunk->data, order_base_2(nr_pages)); pcpu_free_chunk(chunk); }

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static struct page *pcpu_addr_to_page(void *addr) { return virt_to_page(addr); }

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static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai) { size_t nr_pages, alloc_pages; /* all units must be in a single group */ if (ai->nr_groups != 1) { pr_crit("can't handle more than one group\n"); return -EINVAL; } nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT; alloc_pages = roundup_pow_of_two(nr_pages); if (alloc_pages > nr_pages) pr_warn("wasting %zu pages per chunk\n", alloc_pages - nr_pages); return 0; }

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Tejun Heo7895.12%133.33%
Joe Perches44.88%266.67%
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Tejun Heo34498.85%675.00%
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Directory: mm
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