Quelle  decompressor_multi_percpu.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2013
 * Phillip Lougher <phillip@squashfs.org.uk>
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/percpu.h>
#include <linux/local_lock.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "decompressor.h"
#include "squashfs.h"

/*
 * This file implements multi-threaded decompression using percpu
 * variables, one thread per cpu core.
 */

struct squashfs_stream {
 void   *stream;
 local_lock_t lock;
};

static void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
      void *comp_opts)
{
 struct squashfs_stream *stream;
 struct squashfs_stream __percpu *percpu;
 int err, cpu;

 percpu = alloc_percpu(struct squashfs_stream);
 if (percpu == NULL)
  return ERR_PTR(-ENOMEM);

 for_each_possible_cpu(cpu) {
  stream = per_cpu_ptr(percpu, cpu);
  stream->stream = msblk->decompressor->init(msblk, comp_opts);
  if (IS_ERR(stream->stream)) {
   err = PTR_ERR(stream->stream);
   goto out;
  }
  local_lock_init(&stream->lock);
 }

 kfree(comp_opts);
 return (void *)(__force unsigned long) percpu;

out:
 for_each_possible_cpu(cpu) {
  stream = per_cpu_ptr(percpu, cpu);
  if (!IS_ERR_OR_NULL(stream->stream))
   msblk->decompressor->free(stream->stream);
 }
 free_percpu(percpu);
 return ERR_PTR(err);
}

static void squashfs_decompressor_destroy(struct squashfs_sb_info *msblk)
{
 struct squashfs_stream __percpu *percpu =
   (void __percpu *)(unsigned long) msblk->stream;
 struct squashfs_stream *stream;
 int cpu;

 if (msblk->stream) {
  for_each_possible_cpu(cpu) {
   stream = per_cpu_ptr(percpu, cpu);
   msblk->decompressor->free(stream->stream);
  }
  free_percpu(percpu);
 }
}

static int squashfs_decompress(struct squashfs_sb_info *msblk, struct bio *bio,
 int offset, int length, struct squashfs_page_actor *output)
{
 struct squashfs_stream *stream;
 struct squashfs_stream __percpu *percpu =
   (void __percpu *)(unsigned long) msblk->stream;
 int res;

 local_lock(&percpu->lock);
 stream = this_cpu_ptr(percpu);

 res = msblk->decompressor->decompress(msblk, stream->stream, bio,
           offset, length, output);

 local_unlock(&percpu->lock);

 if (res < 0)
  ERROR("%s decompression failed, data probably corrupt\n",
   msblk->decompressor->name);

 return res;
}

static int squashfs_max_decompressors(void)
{
 return num_possible_cpus();
}

const struct squashfs_decompressor_thread_ops squashfs_decompressor_percpu = {
 .create = squashfs_decompressor_create,
 .destroy = squashfs_decompressor_destroy,
 .decompress = squashfs_decompress,
 .max_decompressors = squashfs_max_decompressors,
};