drivers/block/zram/zcomp.c

   1 /*
   2  * Copyright (C) 2014 Sergey Senozhatsky.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/string.h>
  12 #include <linux/err.h>
  13 #include <linux/slab.h>
  14 #include <linux/wait.h>
  15 #include <linux/sched.h>
  16 #include <linux/cpu.h>
  17 #include <linux/crypto.h>
  18
  19 #include "zcomp.h"
  20
  21 static const char * const backends[] = {
  22         "lzo",
  23 #if IS_ENABLED(CONFIG_CRYPTO_LZ4)
  24         "lz4",
  25 #endif
  26 #if IS_ENABLED(CONFIG_CRYPTO_DEFLATE)
  27         "deflate",
  28 #endif
  29 #if IS_ENABLED(CONFIG_CRYPTO_LZ4HC)
  30         "lz4hc",
  31 #endif
  32 #if IS_ENABLED(CONFIG_CRYPTO_842)
  33         "842",
  34 #endif
  35         NULL
  36 };
  37
  38 static void zcomp_strm_free(struct zcomp_strm *zstrm)
  39 {
  40         if (!IS_ERR_OR_NULL(zstrm->tfm))
  41                 crypto_free_comp(zstrm->tfm);
  42         free_pages((unsigned long)zstrm->buffer, 1);
  43         kfree(zstrm);
  44 }
  45
  46 /*
  47  * allocate new zcomp_strm structure with ->tfm initialized by
  48  * backend, return NULL on error
  49  */
  50 static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
  51 {
  52         struct zcomp_strm *zstrm = kmalloc(sizeof(*zstrm), GFP_KERNEL);
  53         if (!zstrm)
  54                 return NULL;
  55
  56         zstrm->tfm = crypto_alloc_comp(comp->name, 0, 0);
  57         /*
  58          * allocate 2 pages. 1 for compressed data, plus 1 extra for the
  59          * case when compressed size is larger than the original one
  60          */
  61         zstrm->buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
  62         if (IS_ERR_OR_NULL(zstrm->tfm) || !zstrm->buffer) {
  63                 zcomp_strm_free(zstrm);
  64                 zstrm = NULL;
  65         }
  66         return zstrm;
  67 }
  68
  69 bool zcomp_available_algorithm(const char *comp)
  70 {
  71         int i;
  72
  73         i = __sysfs_match_string(backends, -1, comp);
  74         if (i >= 0)
  75                 return true;
  76
  77         /*
  78          * Crypto does not ignore a trailing new line symbol,
  79          * so make sure you don't supply a string containing
  80          * one.
  81          * This also means that we permit zcomp initialisation
  82          * with any compressing algorithm known to crypto api.
  83          */
  84         return crypto_has_comp(comp, 0, 0) == 1;
  85 }
  86
  87 /* show available compressors */
  88 ssize_t zcomp_available_show(const char *comp, char *buf)
  89 {
  90         bool known_algorithm = false;
  91         ssize_t sz = 0;
  92         int i = 0;
  93
  94         for (; backends[i]; i++) {
  95                 if (!strcmp(comp, backends[i])) {
  96                         known_algorithm = true;
  97                         sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
  98                                         "[%s] ", backends[i]);
  99                 } else {
 100                         sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
 101                                         "%s ", backends[i]);
 102                 }
 103         }
 104
 105         /*
 106          * Out-of-tree module known to crypto api or a missing
 107          * entry in `backends'.
 108          */
 109         if (!known_algorithm && crypto_has_comp(comp, 0, 0) == 1)
 110                 sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
 111                                 "[%s] ", comp);
 112
 113         sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");
 114         return sz;
 115 }
 116
 117 struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
 118 {
 119         return *get_cpu_ptr(comp->stream);
 120 }
 121
 122 void zcomp_stream_put(struct zcomp *comp)
 123 {
 124         put_cpu_ptr(comp->stream);
 125 }
 126
 127 int zcomp_compress(struct zcomp_strm *zstrm,
 128                 const void *src, unsigned int *dst_len)
 129 {
 130         /*
 131          * Our dst memory (zstrm->buffer) is always `2 * PAGE_SIZE' sized
 132          * because sometimes we can endup having a bigger compressed data
 133          * due to various reasons: for example compression algorithms tend
 134          * to add some padding to the compressed buffer. Speaking of padding,
 135          * comp algorithm `842' pads the compressed length to multiple of 8
 136          * and returns -ENOSP when the dst memory is not big enough, which
 137          * is not something that ZRAM wants to see. We can handle the
 138          * `compressed_size > PAGE_SIZE' case easily in ZRAM, but when we
 139          * receive -ERRNO from the compressing backend we can't help it
 140          * anymore. To make `842' happy we need to tell the exact size of
 141          * the dst buffer, zram_drv will take care of the fact that
 142          * compressed buffer is too big.
 143          */
 144         *dst_len = PAGE_SIZE * 2;
 145
 146         return crypto_comp_compress(zstrm->tfm,
 147                         src, PAGE_SIZE,
 148                         zstrm->buffer, dst_len);
 149 }
 150
 151 int zcomp_decompress(struct zcomp_strm *zstrm,
 152                 const void *src, unsigned int src_len, void *dst)
 153 {
 154         unsigned int dst_len = PAGE_SIZE;
 155
 156         return crypto_comp_decompress(zstrm->tfm,
 157                         src, src_len,
 158                         dst, &dst_len);
 159 }
 160
 161 int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
 162 {
 163         struct zcomp *comp = hlist_entry(node, struct zcomp, node);
 164         struct zcomp_strm *zstrm;
 165
 166         if (WARN_ON(*per_cpu_ptr(comp->stream, cpu)))
 167                 return 0;
 168
 169         zstrm = zcomp_strm_alloc(comp);
 170         if (IS_ERR_OR_NULL(zstrm)) {
 171                 pr_err("Can't allocate a compression stream\n");
 172                 return -ENOMEM;
 173         }
 174         *per_cpu_ptr(comp->stream, cpu) = zstrm;
 175         return 0;
 176 }
 177
 178 int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node)
 179 {
 180         struct zcomp *comp = hlist_entry(node, struct zcomp, node);
 181         struct zcomp_strm *zstrm;
 182
 183         zstrm = *per_cpu_ptr(comp->stream, cpu);
 184         if (!IS_ERR_OR_NULL(zstrm))
 185                 zcomp_strm_free(zstrm);
 186         *per_cpu_ptr(comp->stream, cpu) = NULL;
 187         return 0;
 188 }
 189
 190 static int zcomp_init(struct zcomp *comp)
 191 {
 192         int ret;
 193
 194         comp->stream = alloc_percpu(struct zcomp_strm *);
 195         if (!comp->stream)
 196                 return -ENOMEM;
 197
 198         ret = cpuhp_state_add_instance(CPUHP_ZCOMP_PREPARE, &comp->node);
 199         if (ret < 0)
 200                 goto cleanup;
 201         return 0;
 202
 203 cleanup:
 204         free_percpu(comp->stream);
 205         return ret;
 206 }
 207
 208 void zcomp_destroy(struct zcomp *comp)
 209 {
 210         cpuhp_state_remove_instance(CPUHP_ZCOMP_PREPARE, &comp->node);
 211         free_percpu(comp->stream);
 212         kfree(comp);
 213 }
 214
 215 /*
 216  * search available compressors for requested algorithm.
 217  * allocate new zcomp and initialize it. return compressing
 218  * backend pointer or ERR_PTR if things went bad. ERR_PTR(-EINVAL)
 219  * if requested algorithm is not supported, ERR_PTR(-ENOMEM) in
 220  * case of allocation error, or any other error potentially
 221  * returned by zcomp_init().
 222  */
 223 struct zcomp *zcomp_create(const char *compress)
 224 {
 225         struct zcomp *comp;
 226         int error;
 227
 228         if (!zcomp_available_algorithm(compress))
 229                 return ERR_PTR(-EINVAL);
 230
 231         comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL);
 232         if (!comp)
 233                 return ERR_PTR(-ENOMEM);
 234
 235         comp->name = compress;
 236         error = zcomp_init(comp);
 237         if (error) {
 238                 kfree(comp);
 239                 return ERR_PTR(error);
 240         }
 241         return comp;
 242 }