LXR linux/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 */
  39struct 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 */
  57struct 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
  72extern bool verity_fec_is_enabled(struct dm_verity *v);
  73
  74extern 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
  78extern unsigned verity_fec_status_table(struct dm_verity *v, unsigned sz,
  79                                        char *result, unsigned maxlen);
  80
  81extern void verity_fec_finish_io(struct dm_verity_io *io);
  82extern void verity_fec_init_io(struct dm_verity_io *io);
  83
  84extern bool verity_is_fec_opt_arg(const char *arg_name);
  85extern int verity_fec_parse_opt_args(struct dm_arg_set *as,
  86                                     struct dm_verity *v, unsigned *argc,
  87                                     const char *arg_name);
  88
  89extern void verity_fec_dtr(struct dm_verity *v);
  90
  91extern int verity_fec_ctr_alloc(struct dm_verity *v);
  92extern int verity_fec_ctr(struct dm_verity *v);
  93
  94#else /* !CONFIG_DM_VERITY_FEC */
  95
  96#define DM_VERITY_OPTS_FEC      0
  97
  98static inline bool verity_fec_is_enabled(struct dm_verity *v)
  99{
 100        return false;
 101}
 102
 103static 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
 112static inline unsigned verity_fec_status_table(struct dm_verity *v,
 113                                               unsigned sz, char *result,
 114                                               unsigned maxlen)
 115{
 116        return sz;
 117}
 118
 119static inline void verity_fec_finish_io(struct dm_verity_io *io)
 120{
 121}
 122
 123static inline void verity_fec_init_io(struct dm_verity_io *io)
 124{
 125}
 126
 127static inline bool verity_is_fec_opt_arg(const char *arg_name)
 128{
 129        return false;
 130}
 131
 132static 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
 140static inline void verity_fec_dtr(struct dm_verity *v)
 141{
 142}
 143
 144static inline int verity_fec_ctr_alloc(struct dm_verity *v)
 145{
 146        return 0;
 147}
 148
 149static 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 */
 157