drivers/md/dm-verity-fec.h

   1 /*
   2  * Copyright (C) 2015 Google, Inc.
   3  *
   4  * Author: Sami Tolvanen <samitolvanen@google.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the Free
   8  * Software Foundation; either version 2 of the License, or (at your option)
   9  * any later version.
  10  */
  11
  12 #ifndef DM_VERITY_FEC_H
  13 #define DM_VERITY_FEC_H
  14
  15 #include "dm-verity.h"
  16 #include <linux/rslib.h>
  17
  18 /* Reed-Solomon(M, N) parameters */
  19 #define DM_VERITY_FEC_RSM               255
  20 #define DM_VERITY_FEC_MAX_RSN           253
  21 #define DM_VERITY_FEC_MIN_RSN           231     /* ~10% space overhead */
  22
  23 /* buffers for deinterleaving and decoding */
  24 #define DM_VERITY_FEC_BUF_PREALLOC      1       /* buffers to preallocate */
  25 #define DM_VERITY_FEC_BUF_RS_BITS       4       /* 1 << RS blocks per buffer */
  26 /* we need buffers for at most 1 << block size RS blocks */
  27 #define DM_VERITY_FEC_BUF_MAX \
  28         (1 << (PAGE_SHIFT - DM_VERITY_FEC_BUF_RS_BITS))
  29
  30 /* maximum recursion level for verity_fec_decode */
  31 #define DM_VERITY_FEC_MAX_RECURSION     4
  32
  33 #define DM_VERITY_OPT_FEC_DEV           "use_fec_from_device"
  34 #define DM_VERITY_OPT_FEC_BLOCKS        "fec_blocks"
  35 #define DM_VERITY_OPT_FEC_START         "fec_start"
  36 #define DM_VERITY_OPT_FEC_ROOTS         "fec_roots"
  37
  38 /* configuration */
  39 struct dm_verity_fec {
  40         struct dm_dev *dev;     /* parity data device */
  41         struct dm_bufio_client *data_bufio;     /* for data dev access */
  42         struct dm_bufio_client *bufio;          /* for parity data access */
  43         sector_t start;         /* parity data start in blocks */
  44         sector_t blocks;        /* number of blocks covered */
  45         sector_t rounds;        /* number of interleaving rounds */
  46         sector_t hash_blocks;   /* blocks covered after v->hash_start */
  47         unsigned char roots;    /* number of parity bytes, M-N of RS(M, N) */
  48         unsigned char rsn;      /* N of RS(M, N) */
  49         mempool_t *rs_pool;     /* mempool for fio->rs */
  50         mempool_t *prealloc_pool;       /* mempool for preallocated buffers */
  51         mempool_t *extra_pool;  /* mempool for extra buffers */
  52         mempool_t *output_pool; /* mempool for output */
  53         struct kmem_cache *cache;       /* cache for buffers */
  54 };
  55
  56 /* per-bio data */
  57 struct dm_verity_fec_io {
  58         struct rs_control *rs;  /* Reed-Solomon state */
  59         int erasures[DM_VERITY_FEC_MAX_RSN];    /* erasures for decode_rs8 */
  60         u8 *bufs[DM_VERITY_FEC_BUF_MAX];        /* bufs for deinterleaving */
  61         unsigned nbufs;         /* number of buffers allocated */
  62         u8 *output;             /* buffer for corrected output */
  63         size_t output_pos;
  64         unsigned level;         /* recursion level */
  65 };
  66
  67 #ifdef CONFIG_DM_VERITY_FEC
  68
  69 /* each feature parameter requires a value */
  70 #define DM_VERITY_OPTS_FEC      8
  71
  72 extern bool verity_fec_is_enabled(struct dm_verity *v);
  73
  74 extern int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
  75                              enum verity_block_type type, sector_t block,
  76                              u8 *dest, struct bvec_iter *iter);
  77
  78 extern unsigned verity_fec_status_table(struct dm_verity *v, unsigned sz,
  79                                         char *result, unsigned maxlen);
  80
  81 extern void verity_fec_finish_io(struct dm_verity_io *io);
  82 extern void verity_fec_init_io(struct dm_verity_io *io);
  83
  84 extern bool verity_is_fec_opt_arg(const char *arg_name);
  85 extern int verity_fec_parse_opt_args(struct dm_arg_set *as,
  86                                      struct dm_verity *v, unsigned *argc,
  87                                      const char *arg_name);
  88
  89 extern void verity_fec_dtr(struct dm_verity *v);
  90
  91 extern int verity_fec_ctr_alloc(struct dm_verity *v);
  92 extern int verity_fec_ctr(struct dm_verity *v);
  93
  94 #else /* !CONFIG_DM_VERITY_FEC */
  95
  96 #define DM_VERITY_OPTS_FEC      0
  97
  98 static inline bool verity_fec_is_enabled(struct dm_verity *v)
  99 {
 100         return false;
 101 }
 102
 103 static inline int verity_fec_decode(struct dm_verity *v,
 104                                     struct dm_verity_io *io,
 105                                     enum verity_block_type type,
 106                                     sector_t block, u8 *dest,
 107                                     struct bvec_iter *iter)
 108 {
 109         return -EOPNOTSUPP;
 110 }
 111
 112 static inline unsigned verity_fec_status_table(struct dm_verity *v,
 113                                                unsigned sz, char *result,
 114                                                unsigned maxlen)
 115 {
 116         return sz;
 117 }
 118
 119 static inline void verity_fec_finish_io(struct dm_verity_io *io)
 120 {
 121 }
 122
 123 static inline void verity_fec_init_io(struct dm_verity_io *io)
 124 {
 125 }
 126
 127 static inline bool verity_is_fec_opt_arg(const char *arg_name)
 128 {
 129         return false;
 130 }
 131
 132 static inline int verity_fec_parse_opt_args(struct dm_arg_set *as,
 133                                             struct dm_verity *v,
 134                                             unsigned *argc,
 135                                             const char *arg_name)
 136 {
 137         return -EINVAL;
 138 }
 139
 140 static inline void verity_fec_dtr(struct dm_verity *v)
 141 {
 142 }
 143
 144 static inline int verity_fec_ctr_alloc(struct dm_verity *v)
 145 {
 146         return 0;
 147 }
 148
 149 static inline int verity_fec_ctr(struct dm_verity *v)
 150 {
 151         return 0;
 152 }
 153
 154 #endif /* CONFIG_DM_VERITY_FEC */
 155
 156 #endif /* DM_VERITY_FEC_H */