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 = 0;
  72
  73         while (backends[i]) {
  74                 if (sysfs_streq(comp, backends[i]))
  75                         return true;
  76                 i++;
  77         }
  78
  79         /*
  80          * Crypto does not ignore a trailing new line symbol,
  81          * so make sure you don't supply a string containing
  82          * one.
  83          * This also means that we permit zcomp initialisation
  84          * with any compressing algorithm known to crypto api.
  85          */
  86         return crypto_has_comp(comp, 0, 0) == 1;
  87 }
  88
  89 /* show available compressors */
  90 ssize_t zcomp_available_show(const char *comp, char *buf)
  91 {
  92         bool known_algorithm = false;
  93         ssize_t sz = 0;
  94         int i = 0;
  95
  96         for (; backends[i]; i++) {
  97                 if (!strcmp(comp, backends[i])) {
  98                         known_algorithm = true;
  99                         sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
 100                                         "[%s] ", backends[i]);
 101                 } else {
 102                         sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
 103                                         "%s ", backends[i]);
 104                 }
 105         }
 106
 107         /*
 108          * Out-of-tree module known to crypto api or a missing
 109          * entry in `backends'.
 110          */
 111         if (!known_algorithm && crypto_has_comp(comp, 0, 0) == 1)
 112                 sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
 113                                 "[%s] ", comp);
 114
 115         sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");
 116         return sz;
 117 }
 118
 119 struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
 120 {
 121         return *get_cpu_ptr(comp->stream);
 122 }
 123
 124 void zcomp_stream_put(struct zcomp *comp)
 125 {
 126         put_cpu_ptr(comp->stream);
 127 }
 128
 129 int zcomp_compress(struct zcomp_strm *zstrm,
 130                 const void *src, unsigned int *dst_len)
 131 {
 132         /*
 133          * Our dst memory (zstrm->buffer) is always `2 * PAGE_SIZE' sized
 134          * because sometimes we can endup having a bigger compressed data
 135          * due to various reasons: for example compression algorithms tend
 136          * to add some padding to the compressed buffer. Speaking of padding,
 137          * comp algorithm `842' pads the compressed length to multiple of 8
 138          * and returns -ENOSP when the dst memory is not big enough, which
 139          * is not something that ZRAM wants to see. We can handle the
 140          * `compressed_size > PAGE_SIZE' case easily in ZRAM, but when we
 141          * receive -ERRNO from the compressing backend we can't help it
 142          * anymore. To make `842' happy we need to tell the exact size of
 143          * the dst buffer, zram_drv will take care of the fact that
 144          * compressed buffer is too big.
 145          */
 146         *dst_len = PAGE_SIZE * 2;
 147
 148         return crypto_comp_compress(zstrm->tfm,
 149                         src, PAGE_SIZE,
 150                         zstrm->buffer, dst_len);
 151 }
 152
 153 int zcomp_decompress(struct zcomp_strm *zstrm,
 154                 const void *src, unsigned int src_len, void *dst)
 155 {
 156         unsigned int dst_len = PAGE_SIZE;
 157
 158         return crypto_comp_decompress(zstrm->tfm,
 159                         src, src_len,
 160                         dst, &dst_len);
 161 }
 162
 163 static int __zcomp_cpu_notifier(struct zcomp *comp,
 164                 unsigned long action, unsigned long cpu)
 165 {
 166         struct zcomp_strm *zstrm;
 167
 168         switch (action) {
 169         case CPU_UP_PREPARE:
 170                 if (WARN_ON(*per_cpu_ptr(comp->stream, cpu)))
 171                         break;
 172                 zstrm = zcomp_strm_alloc(comp);
 173                 if (IS_ERR_OR_NULL(zstrm)) {
 174                         pr_err("Can't allocate a compression stream\n");
 175                         return NOTIFY_BAD;
 176                 }
 177                 *per_cpu_ptr(comp->stream, cpu) = zstrm;
 178                 break;
 179         case CPU_DEAD:
 180         case CPU_UP_CANCELED:
 181                 zstrm = *per_cpu_ptr(comp->stream, cpu);
 182                 if (!IS_ERR_OR_NULL(zstrm))
 183                         zcomp_strm_free(zstrm);
 184                 *per_cpu_ptr(comp->stream, cpu) = NULL;
 185                 break;
 186         default:
 187                 break;
 188         }
 189         return NOTIFY_OK;
 190 }
 191
 192 static int zcomp_cpu_notifier(struct notifier_block *nb,
 193                 unsigned long action, void *pcpu)
 194 {
 195         unsigned long cpu = (unsigned long)pcpu;
 196         struct zcomp *comp = container_of(nb, typeof(*comp), notifier);
 197
 198         return __zcomp_cpu_notifier(comp, action, cpu);
 199 }
 200
 201 static int zcomp_init(struct zcomp *comp)
 202 {
 203         unsigned long cpu;
 204         int ret;
 205
 206         comp->notifier.notifier_call = zcomp_cpu_notifier;
 207
 208         comp->stream = alloc_percpu(struct zcomp_strm *);
 209         if (!comp->stream)
 210                 return -ENOMEM;
 211
 212         cpu_notifier_register_begin();
 213         for_each_online_cpu(cpu) {
 214                 ret = __zcomp_cpu_notifier(comp, CPU_UP_PREPARE, cpu);
 215                 if (ret == NOTIFY_BAD)
 216                         goto cleanup;
 217         }
 218         __register_cpu_notifier(&comp->notifier);
 219         cpu_notifier_register_done();
 220         return 0;
 221
 222 cleanup:
 223         for_each_online_cpu(cpu)
 224                 __zcomp_cpu_notifier(comp, CPU_UP_CANCELED, cpu);
 225         cpu_notifier_register_done();
 226         return -ENOMEM;
 227 }
 228
 229 void zcomp_destroy(struct zcomp *comp)
 230 {
 231         unsigned long cpu;
 232
 233         cpu_notifier_register_begin();
 234         for_each_online_cpu(cpu)
 235                 __zcomp_cpu_notifier(comp, CPU_UP_CANCELED, cpu);
 236         __unregister_cpu_notifier(&comp->notifier);
 237         cpu_notifier_register_done();
 238
 239         free_percpu(comp->stream);
 240         kfree(comp);
 241 }
 242
 243 /*
 244  * search available compressors for requested algorithm.
 245  * allocate new zcomp and initialize it. return compressing
 246  * backend pointer or ERR_PTR if things went bad. ERR_PTR(-EINVAL)
 247  * if requested algorithm is not supported, ERR_PTR(-ENOMEM) in
 248  * case of allocation error, or any other error potentially
 249  * returned by zcomp_init().
 250  */
 251 struct zcomp *zcomp_create(const char *compress)
 252 {
 253         struct zcomp *comp;
 254         int error;
 255
 256         if (!zcomp_available_algorithm(compress))
 257                 return ERR_PTR(-EINVAL);
 258
 259         comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL);
 260         if (!comp)
 261                 return ERR_PTR(-ENOMEM);
 262
 263         comp->name = compress;
 264         error = zcomp_init(comp);
 265         if (error) {
 266                 kfree(comp);
 267                 return ERR_PTR(error);
 268         }
 269         return comp;
 270 }