target/linux/generic/pending-4.9/411-mtd-partial_eraseblock_write.patch

   1 From: Felix Fietkau <nbd@nbd.name>
   2 Subject: mtd: implement write support for partitions covering only a part of an eraseblock (buffer data that would otherwise be erased)
   3
   4 lede-commit: 87a8e8ac1067f58ba831c4aae443f3655c31cd80
   5 Signed-off-by: Felix Fietkau <nbd@nbd.name>
   6 ---
   7  drivers/mtd/mtdpart.c   | 90 ++++++++++++++++++++++++++++++++++++++++++++-----
   8  include/linux/mtd/mtd.h |  4 +++
   9  2 files changed, 85 insertions(+), 9 deletions(-)
  10
  11 --- a/drivers/mtd/mtdpart.c
  12 +++ b/drivers/mtd/mtdpart.c
  13 @@ -37,6 +37,8 @@
  14  #include "mtdcore.h"
  15  #include "mtdsplit/mtdsplit.h"
  16
  17 +#define MTD_ERASE_PARTIAL      0x8000 /* partition only covers parts of an erase block */
  18 +
  19  /* Our partition linked list */
  20  static LIST_HEAD(mtd_partitions);
  21  static DEFINE_MUTEX(mtd_partitions_mutex);
  22 @@ -246,13 +248,61 @@ static int part_erase(struct mtd_info *m
  23         struct mtd_part *part = mtd_to_part(mtd);
  24         int ret;
  25
  26 +
  27 +       instr->partial_start = false;
  28 +       if (mtd->flags & MTD_ERASE_PARTIAL) {
  29 +               size_t readlen = 0;
  30 +               u64 mtd_ofs;
  31 +
  32 +               instr->erase_buf = kmalloc(part->parent->erasesize, GFP_ATOMIC);
  33 +               if (!instr->erase_buf)
  34 +                       return -ENOMEM;
  35 +
  36 +               mtd_ofs = part->offset + instr->addr;
  37 +               instr->erase_buf_ofs = do_div(mtd_ofs, part->parent->erasesize);
  38 +
  39 +               if (instr->erase_buf_ofs > 0) {
  40 +                       instr->addr -= instr->erase_buf_ofs;
  41 +                       ret = mtd_read(part->parent,
  42 +                               instr->addr + part->offset,
  43 +                               part->parent->erasesize,
  44 +                               &readlen, instr->erase_buf);
  45 +
  46 +                       instr->len += instr->erase_buf_ofs;
  47 +                       instr->partial_start = true;
  48 +               } else {
  49 +                       mtd_ofs = part->offset + part->mtd.size;
  50 +                       instr->erase_buf_ofs = part->parent->erasesize -
  51 +                               do_div(mtd_ofs, part->parent->erasesize);
  52 +
  53 +                       if (instr->erase_buf_ofs > 0) {
  54 +                               instr->len += instr->erase_buf_ofs;
  55 +                               ret = mtd_read(part->parent,
  56 +                                       part->offset + instr->addr +
  57 +                                       instr->len - part->parent->erasesize,
  58 +                                       part->parent->erasesize, &readlen,
  59 +                                       instr->erase_buf);
  60 +                       } else {
  61 +                               ret = 0;
  62 +                       }
  63 +               }
  64 +               if (ret < 0) {
  65 +                       kfree(instr->erase_buf);
  66 +                       return ret;
  67 +               }
  68 +
  69 +       }
  70 +
  71         instr->addr += part->offset;
  72         ret = part->parent->_erase(part->parent, instr);
  73         if (ret) {
  74                 if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
  75                         instr->fail_addr -= part->offset;
  76                 instr->addr -= part->offset;
  77 +               if (mtd->flags & MTD_ERASE_PARTIAL)
  78 +                       kfree(instr->erase_buf);
  79         }
  80 +
  81         return ret;
  82  }
  83
  84 @@ -260,6 +310,25 @@ void mtd_erase_callback(struct erase_inf
  85  {
  86         if (instr->mtd->_erase == part_erase) {
  87                 struct mtd_part *part = mtd_to_part(instr->mtd);
  88 +               size_t wrlen = 0;
  89 +
  90 +               if (instr->mtd->flags & MTD_ERASE_PARTIAL) {
  91 +                       if (instr->partial_start) {
  92 +                               part->parent->_write(part->parent,
  93 +                                       instr->addr, instr->erase_buf_ofs,
  94 +                                       &wrlen, instr->erase_buf);
  95 +                               instr->addr += instr->erase_buf_ofs;
  96 +                       } else {
  97 +                               instr->len -= instr->erase_buf_ofs;
  98 +                               part->parent->_write(part->parent,
  99 +                                       instr->addr + instr->len,
 100 +                                       instr->erase_buf_ofs, &wrlen,
 101 +                                       instr->erase_buf +
 102 +                                       part->parent->erasesize -
 103 +                                       instr->erase_buf_ofs);
 104 +                       }
 105 +                       kfree(instr->erase_buf);
 106 +               }
 107
 108                 if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
 109                         instr->fail_addr -= part->offset;
 110 @@ -566,19 +635,22 @@ static struct mtd_part *allocate_partiti
 111         remainder = do_div(tmp, wr_alignment);
 112         if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
 113                 /* Doesn't start on a boundary of major erase size */
 114 -               /* FIXME: Let it be writable if it is on a boundary of
 115 -                * _minor_ erase size though */
 116 -               slave->mtd.flags &= ~MTD_WRITEABLE;
 117 -               printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase/write block boundary -- force read-only\n",
 118 -                       part->name);
 119 +               slave->mtd.flags |= MTD_ERASE_PARTIAL;
 120 +               if (((u32)slave->mtd.size) > parent->erasesize)
 121 +                       slave->mtd.flags &= ~MTD_WRITEABLE;
 122 +               else
 123 +                       slave->mtd.erasesize = slave->mtd.size;
 124         }
 125
 126 -       tmp = slave->mtd.size;
 127 +       tmp = slave->offset + slave->mtd.size;
 128         remainder = do_div(tmp, wr_alignment);
 129         if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
 130 -               slave->mtd.flags &= ~MTD_WRITEABLE;
 131 -               printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase/write block -- force read-only\n",
 132 -                       part->name);
 133 +               slave->mtd.flags |= MTD_ERASE_PARTIAL;
 134 +
 135 +               if ((u32)slave->mtd.size > parent->erasesize)
 136 +                       slave->mtd.flags &= ~MTD_WRITEABLE;
 137 +               else
 138 +                       slave->mtd.erasesize = slave->mtd.size;
 139         }
 140
 141         mtd_set_ooblayout(&slave->mtd, &part_ooblayout_ops);
 142 --- a/include/linux/mtd/mtd.h
 143 +++ b/include/linux/mtd/mtd.h
 144 @@ -55,6 +55,10 @@ struct erase_info {
 145         u_long priv;
 146         u_char state;
 147         struct erase_info *next;
 148 +
 149 +       u8 *erase_buf;
 150 +       u32 erase_buf_ofs;
 151 +       bool partial_start;
 152  };
 153
 154  struct mtd_erase_region_info {