target/linux/generic/pending-4.19/411-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 @@ -36,6 +36,8 @@
  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 @@ -220,11 +222,77 @@ static int part_erase(struct mtd_info *m
  23  {
  24         struct mtd_part *part = mtd_to_part(mtd);
  25         int ret;
  26 +       size_t wrlen = 0;
  27 +       u8 *erase_buf = NULL;
  28 +       u32 erase_buf_ofs = 0;
  29 +       bool partial_start = false;
  30 +
  31 +       if (mtd->flags & MTD_ERASE_PARTIAL) {
  32 +               size_t readlen = 0;
  33 +               u64 mtd_ofs;
  34 +
  35 +               erase_buf = kmalloc(part->parent->erasesize, GFP_ATOMIC);
  36 +               if (!erase_buf)
  37 +                       return -ENOMEM;
  38 +
  39 +               mtd_ofs = part->offset + instr->addr;
  40 +               erase_buf_ofs = do_div(mtd_ofs, part->parent->erasesize);
  41 +
  42 +               if (erase_buf_ofs > 0) {
  43 +                       instr->addr -= erase_buf_ofs;
  44 +                       ret = mtd_read(part->parent,
  45 +                               instr->addr + part->offset,
  46 +                               part->parent->erasesize,
  47 +                               &readlen, erase_buf);
  48 +
  49 +                       instr->len += erase_buf_ofs;
  50 +                       partial_start = true;
  51 +               } else {
  52 +                       mtd_ofs = part->offset + part->mtd.size;
  53 +                       erase_buf_ofs = part->parent->erasesize -
  54 +                               do_div(mtd_ofs, part->parent->erasesize);
  55 +
  56 +                       if (erase_buf_ofs > 0) {
  57 +                               instr->len += erase_buf_ofs;
  58 +                               ret = mtd_read(part->parent,
  59 +                                       part->offset + instr->addr +
  60 +                                       instr->len - part->parent->erasesize,
  61 +                                       part->parent->erasesize, &readlen,
  62 +                                       erase_buf);
  63 +                       } else {
  64 +                               ret = 0;
  65 +                       }
  66 +               }
  67 +               if (ret < 0) {
  68 +                       kfree(erase_buf);
  69 +                       return ret;
  70 +               }
  71 +
  72 +       }
  73
  74         instr->addr += part->offset;
  75         ret = part->parent->_erase(part->parent, instr);
  76         if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
  77                 instr->fail_addr -= part->offset;
  78 +
  79 +       if (mtd->flags & MTD_ERASE_PARTIAL) {
  80 +               if (partial_start) {
  81 +                       part->parent->_write(part->parent,
  82 +                               instr->addr, erase_buf_ofs,
  83 +                               &wrlen, erase_buf);
  84 +                       instr->addr += erase_buf_ofs;
  85 +               } else {
  86 +                       instr->len -= erase_buf_ofs;
  87 +                       part->parent->_write(part->parent,
  88 +                               instr->addr + instr->len,
  89 +                               erase_buf_ofs, &wrlen,
  90 +                               erase_buf +
  91 +                               part->parent->erasesize -
  92 +                               erase_buf_ofs);
  93 +               }
  94 +               kfree(erase_buf);
  95 +       }
  96 +
  97         instr->addr -= part->offset;
  98
  99         return ret;
 100 @@ -539,19 +607,22 @@ static struct mtd_part *allocate_partiti
 101         remainder = do_div(tmp, wr_alignment);
 102         if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
 103                 /* Doesn't start on a boundary of major erase size */
 104 -               /* FIXME: Let it be writable if it is on a boundary of
 105 -                * _minor_ erase size though */
 106 -               slave->mtd.flags &= ~MTD_WRITEABLE;
 107 -               printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase/write block boundary -- force read-only\n",
 108 -                       part->name);
 109 +               slave->mtd.flags |= MTD_ERASE_PARTIAL;
 110 +               if (((u32)slave->mtd.size) > parent->erasesize)
 111 +                       slave->mtd.flags &= ~MTD_WRITEABLE;
 112 +               else
 113 +                       slave->mtd.erasesize = slave->mtd.size;
 114         }
 115
 116         tmp = part_absolute_offset(parent) + slave->offset + slave->mtd.size;
 117         remainder = do_div(tmp, wr_alignment);
 118         if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
 119 -               slave->mtd.flags &= ~MTD_WRITEABLE;
 120 -               printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase/write block -- force read-only\n",
 121 -                       part->name);
 122 +               slave->mtd.flags |= MTD_ERASE_PARTIAL;
 123 +
 124 +               if ((u32)slave->mtd.size > parent->erasesize)
 125 +                       slave->mtd.flags &= ~MTD_WRITEABLE;
 126 +               else
 127 +                       slave->mtd.erasesize = slave->mtd.size;
 128         }
 129
 130         mtd_set_ooblayout(&slave->mtd, &part_ooblayout_ops);