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 #ifdef CONFIG_ZRAM_LZ4_COMPRESS
  24         "lz4",
  25 #endif
  26         NULL
  27 };
  28
  29 static const char *find_backend(const char *compress)
  30 {
  31         int i = 0;
  32         while (backends[i]) {
  33                 if (sysfs_streq(compress, backends[i]))
  34                         break;
  35                 i++;
  36         }
  37         return backends[i];
  38 }
  39
  40 static void zcomp_strm_free(struct zcomp_strm *zstrm)
  41 {
  42         if (!IS_ERR_OR_NULL(zstrm->tfm))
  43                 crypto_free_comp(zstrm->tfm);
  44         free_pages((unsigned long)zstrm->buffer, 1);
  45         kfree(zstrm);
  46 }
  47
  48 /*
  49  * allocate new zcomp_strm structure with ->tfm initialized by
  50  * backend, return NULL on error
  51  */
  52 static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp, gfp_t flags)
  53 {
  54         struct zcomp_strm *zstrm = kmalloc(sizeof(*zstrm), flags);
  55         if (!zstrm)
  56                 return NULL;
  57
  58         zstrm->tfm = crypto_alloc_comp(comp->name, 0, 0);
  59         /*
  60          * allocate 2 pages. 1 for compressed data, plus 1 extra for the
  61          * case when compressed size is larger than the original one
  62          */
  63         zstrm->buffer = (void *)__get_free_pages(flags | __GFP_ZERO, 1);
  64         if (IS_ERR_OR_NULL(zstrm->tfm) || !zstrm->buffer) {
  65                 zcomp_strm_free(zstrm);
  66                 zstrm = NULL;
  67         }
  68         return zstrm;
  69 }
  70
  71 /* show available compressors */
  72 ssize_t zcomp_available_show(const char *comp, char *buf)
  73 {
  74         ssize_t sz = 0;
  75         int i = 0;
  76
  77         while (backends[i]) {
  78                 if (!strcmp(comp, backends[i]))
  79                         sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
  80                                         "[%s] ", backends[i]);
  81                 else
  82                         sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
  83                                         "%s ", backends[i]);
  84                 i++;
  85         }
  86         sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");
  87         return sz;
  88 }
  89
  90 bool zcomp_available_algorithm(const char *comp)
  91 {
  92         return find_backend(comp) != NULL;
  93 }
  94
  95 struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
  96 {
  97         return *get_cpu_ptr(comp->stream);
  98 }
  99
 100 void zcomp_stream_put(struct zcomp *comp)
 101 {
 102         put_cpu_ptr(comp->stream);
 103 }
 104
 105 int zcomp_compress(struct zcomp_strm *zstrm,
 106                 const void *src, unsigned int *dst_len)
 107 {
 108         /*
 109          * Our dst memory (zstrm->buffer) is always `2 * PAGE_SIZE' sized
 110          * because sometimes we can endup having a bigger compressed data
 111          * due to various reasons: for example compression algorithms tend
 112          * to add some padding to the compressed buffer. Speaking of padding,
 113          * comp algorithm `842' pads the compressed length to multiple of 8
 114          * and returns -ENOSP when the dst memory is not big enough, which
 115          * is not something that ZRAM wants to see. We can handle the
 116          * `compressed_size > PAGE_SIZE' case easily in ZRAM, but when we
 117          * receive -ERRNO from the compressing backend we can't help it
 118          * anymore. To make `842' happy we need to tell the exact size of
 119          * the dst buffer, zram_drv will take care of the fact that
 120          * compressed buffer is too big.
 121          */
 122         *dst_len = PAGE_SIZE * 2;
 123
 124         return crypto_comp_compress(zstrm->tfm,
 125                         src, PAGE_SIZE,
 126                         zstrm->buffer, dst_len);
 127 }
 128
 129 int zcomp_decompress(struct zcomp_strm *zstrm,
 130                 const void *src, unsigned int src_len, void *dst)
 131 {
 132         unsigned int dst_len = PAGE_SIZE;
 133
 134         return crypto_comp_decompress(zstrm->tfm,
 135                         src, src_len,
 136                         dst, &dst_len);
 137 }
 138
 139 static int __zcomp_cpu_notifier(struct zcomp *comp,
 140                 unsigned long action, unsigned long cpu)
 141 {
 142         struct zcomp_strm *zstrm;
 143
 144         switch (action) {
 145         case CPU_UP_PREPARE:
 146                 if (WARN_ON(*per_cpu_ptr(comp->stream, cpu)))
 147                         break;
 148                 zstrm = zcomp_strm_alloc(comp, GFP_KERNEL);
 149                 if (IS_ERR_OR_NULL(zstrm)) {
 150                         pr_err("Can't allocate a compression stream\n");
 151                         return NOTIFY_BAD;
 152                 }
 153                 *per_cpu_ptr(comp->stream, cpu) = zstrm;
 154                 break;
 155         case CPU_DEAD:
 156         case CPU_UP_CANCELED:
 157                 zstrm = *per_cpu_ptr(comp->stream, cpu);
 158                 if (!IS_ERR_OR_NULL(zstrm))
 159                         zcomp_strm_free(zstrm);
 160                 *per_cpu_ptr(comp->stream, cpu) = NULL;
 161                 break;
 162         default:
 163                 break;
 164         }
 165         return NOTIFY_OK;
 166 }
 167
 168 static int zcomp_cpu_notifier(struct notifier_block *nb,
 169                 unsigned long action, void *pcpu)
 170 {
 171         unsigned long cpu = (unsigned long)pcpu;
 172         struct zcomp *comp = container_of(nb, typeof(*comp), notifier);
 173
 174         return __zcomp_cpu_notifier(comp, action, cpu);
 175 }
 176
 177 static int zcomp_init(struct zcomp *comp)
 178 {
 179         unsigned long cpu;
 180         int ret;
 181
 182         comp->notifier.notifier_call = zcomp_cpu_notifier;
 183
 184         comp->stream = alloc_percpu(struct zcomp_strm *);
 185         if (!comp->stream)
 186                 return -ENOMEM;
 187
 188         cpu_notifier_register_begin();
 189         for_each_online_cpu(cpu) {
 190                 ret = __zcomp_cpu_notifier(comp, CPU_UP_PREPARE, cpu);
 191                 if (ret == NOTIFY_BAD)
 192                         goto cleanup;
 193         }
 194         __register_cpu_notifier(&comp->notifier);
 195         cpu_notifier_register_done();
 196         return 0;
 197
 198 cleanup:
 199         for_each_online_cpu(cpu)
 200                 __zcomp_cpu_notifier(comp, CPU_UP_CANCELED, cpu);
 201         cpu_notifier_register_done();
 202         return -ENOMEM;
 203 }
 204
 205 void zcomp_destroy(struct zcomp *comp)
 206 {
 207         unsigned long cpu;
 208
 209         cpu_notifier_register_begin();
 210         for_each_online_cpu(cpu)
 211                 __zcomp_cpu_notifier(comp, CPU_UP_CANCELED, cpu);
 212         __unregister_cpu_notifier(&comp->notifier);
 213         cpu_notifier_register_done();
 214
 215         free_percpu(comp->stream);
 216         kfree(comp);
 217 }
 218
 219 /*
 220  * search available compressors for requested algorithm.
 221  * allocate new zcomp and initialize it. return compressing
 222  * backend pointer or ERR_PTR if things went bad. ERR_PTR(-EINVAL)
 223  * if requested algorithm is not supported, ERR_PTR(-ENOMEM) in
 224  * case of allocation error, or any other error potentially
 225  * returned by zcomp_init().
 226  */
 227 struct zcomp *zcomp_create(const char *compress)
 228 {
 229         struct zcomp *comp;
 230         const char *backend;
 231         int error;
 232
 233         backend = find_backend(compress);
 234         if (!backend)
 235                 return ERR_PTR(-EINVAL);
 236
 237         comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL);
 238         if (!comp)
 239                 return ERR_PTR(-ENOMEM);
 240
 241         comp->name = backend;
 242         error = zcomp_init(comp);
 243         if (error) {
 244                 kfree(comp);
 245                 return ERR_PTR(error);
 246         }
 247         return comp;
 248 }