1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* General filesystem local caching manager
  3 *
  4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
  5 * Written by David Howells (dhowells@redhat.com)
  6 */
  7
  8#define FSCACHE_DEBUG_LEVEL CACHE
  9#include <linux/module.h>
 10#include <linux/init.h>
 11#include "internal.h"
 12#define CREATE_TRACE_POINTS
 13#include <trace/events/fscache.h>
 14
 15EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache);
 16EXPORT_TRACEPOINT_SYMBOL(fscache_access_volume);
 17EXPORT_TRACEPOINT_SYMBOL(fscache_access);
 18
 19struct workqueue_struct *fscache_wq;
 20EXPORT_SYMBOL(fscache_wq);
 21
 22/*
 23 * Mixing scores (in bits) for (7,20):
 24 * Input delta: 1-bit      2-bit
 25 * 1 round:     330.3     9201.6
 26 * 2 rounds:   1246.4    25475.4
 27 * 3 rounds:   1907.1    31295.1
 28 * 4 rounds:   2042.3    31718.6
 29 * Perfect:    2048      31744
 30 *            (32*64)   (32*31/2 * 64)
 31 */
 32#define HASH_MIX(x, y, a)	\
 33	(	x ^= (a),	\
 34	y ^= x,	x = rol32(x, 7),\
 35	x += y,	y = rol32(y,20),\
 36	y *= 9			)
 37
 38static inline unsigned int fold_hash(unsigned long x, unsigned long y)
 39{
 40	/* Use arch-optimized multiply if one exists */
 41	return __hash_32(y ^ __hash_32(x));
 42}
 43
 44/*
 45 * Generate a hash.  This is derived from full_name_hash(), but we want to be
 46 * sure it is arch independent and that it doesn't change as bits of the
 47 * computed hash value might appear on disk.  The caller must guarantee that
 48 * the source data is a multiple of four bytes in size.
 49 */
 50unsigned int fscache_hash(unsigned int salt, const void *data, size_t len)
 51{
 52	const __le32 *p = data;
 53	unsigned int a, x = 0, y = salt, n = len / sizeof(__le32);
 54
 55	for (; n; n--) {
 56		a = le32_to_cpu(*p++);
 57		HASH_MIX(x, y, a);
 58	}
 59	return fold_hash(x, y);
 60}
 61
 62/*
 63 * initialise the fs caching module
 64 */
 65int __init fscache_init(void)
 66{
 67	int ret = -ENOMEM;
 68
 69	fscache_wq = alloc_workqueue("fscache", WQ_UNBOUND | WQ_FREEZABLE, 0);
 70	if (!fscache_wq)
 71		goto error_wq;
 72
 73	ret = fscache_proc_init();
 74	if (ret < 0)
 75		goto error_proc;
 76
 77	fscache_cookie_jar = kmem_cache_create("fscache_cookie_jar",
 78					       sizeof(struct fscache_cookie),
 79					       0, 0, NULL);
 80	if (!fscache_cookie_jar) {
 81		pr_notice("Failed to allocate a cookie jar\n");
 82		ret = -ENOMEM;
 83		goto error_cookie_jar;
 84	}
 85
 86	pr_notice("FS-Cache loaded\n");
 87	return 0;
 88
 89error_cookie_jar:
 90	fscache_proc_cleanup();
 91error_proc:
 92	destroy_workqueue(fscache_wq);
 93error_wq:
 94	return ret;
 95}
 96
 97/*
 98 * clean up on module removal
 99 */
100void __exit fscache_exit(void)
101{
102	_enter("");
103
104	kmem_cache_destroy(fscache_cookie_jar);
105	fscache_proc_cleanup();
106	destroy_workqueue(fscache_wq);
107	pr_notice("FS-Cache unloaded\n");
108}