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Reworked tag encoding a little bit

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Mainly to make room for some future planned stuff:

- Moved the mroot's redund bits from LFSR_TAG_GEOMETRY to
  LFSR_TAG_MAGIC:

    LFSR_TAG_MAGIC        0x003r  v--- ---- --11 --rr

  This has the benefit of living in a fixed location (off=0x5), which
  may make mounting/debugging easier. It also makes LFSR_TAG_GEOMETRY
  less of a special case (LFSR_TAG_MAGIC is already a _very_ special
  case).

  Unfortunately, this does get in the way of our previous magic=0x3
  encoding. To compensate (and to avoid conflicts with LFSR_TAG_NULL),
  I've added the 0x3_ prefix. This has the funny side-effect of
  rendering redunds 0-3 as ascii 0-3 (0x30-0x33), which is a complete
  accident but may actually be useful when debugging.

  Currently all config tags fit in the 0x3_ prefix, which is nice for
  debugging but not a hard requirement.

- Flipped LFSR_TAG_FILELIMIT/NAMELIMIT:

    LFSR_TAG_FILELIMIT    0x0039  v--- ---- --11 1--1
    LFSR_TAG_NAMELIMIT    0x003a  v--- ---- --11 1-1-

  The file limit is a _bit_ more fundamental. It's effectively the
  required integer size for the filesystem.

  These may also be followed by LFSR_TAG_ATTRLIMIT based on how future
  attr revisits go.

- Rearranged struct tags so that LFSR_TAG_BRANCH = 0x300:

    LFSR_TAG_BRANCH       0x030r  v--- --11 ---- --rr
    LFSR_TAG_DATA         0x0304  v--- --11 ---- -1--
    LFSR_TAG_BLOCK        0x0308  v--- --11 ---- 1err
    LFSR_TAG_DDKEY*       0x0310  v--- --11 ---1 ----
    LFSR_TAG_DID          0x0314  v--- --11 ---1 -1--
    LFSR_TAG_BSHRUB       0x0318  v--- --11 ---1 1---
    LFSR_TAG_BTREE        0x031c  v--- --11 ---1 11rr
    LFSR_TAG_MROOT        0x032r  v--- --11 --1- --rr
    LFSR_TAG_MDIR         0x0324  v--- --11 --1- -1rr
    LFSR_TAG_MTREE        0x032c  v--- --11 --1- 11rr

    *Planned

  LFSR_TAG_BRANCH is a very special tag when it comes to bshrub/btree
  traversal, so I think it deserves the subtype=0 slot.

  This also just makes everything fit together better, and makes room
  for the future planned ddkey tag.

Code changes minimal:

           code          stack          ctx
  before: 35728           2440          640
  after:  35732 (+0.0%)   2440 (+0.0%)  640 (+0.0%)
This commit is contained in:
Christopher Haster
2025-04-27 11:25:53 -05:00
parent 237ca859d5
commit d308ec8322
9 changed files with 212 additions and 211 deletions
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lfs.c
+47 -46
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@@ -1096,14 +1096,15 @@ enum lfsr_tag {
// config tags
LFSR_TAG_CONFIG = 0x0000,
LFSR_TAG_MAGIC = 0x0003,
LFSR_TAG_VERSION = 0x0004,
LFSR_TAG_RCOMPAT = 0x0005,
LFSR_TAG_WCOMPAT = 0x0006,
LFSR_TAG_OCOMPAT = 0x0007,
LFSR_TAG_GEOMETRY = 0x0009,
LFSR_TAG_NAMELIMIT = 0x000c,
LFSR_TAG_FILELIMIT = 0x000d,
LFSR_TAG_MAGIC = 0x0031,
LFSR_TAG_VERSION = 0x0034,
LFSR_TAG_RCOMPAT = 0x0035,
LFSR_TAG_WCOMPAT = 0x0036,
LFSR_TAG_OCOMPAT = 0x0037,
LFSR_TAG_GEOMETRY = 0x0038,
LFSR_TAG_FILELIMIT = 0x0039,
LFSR_TAG_NAMELIMIT = 0x003a,
LFSR_TAG_UNKNOWNCONFIG = 0x003b,
// global-state tags
LFSR_TAG_GDELTA = 0x0100,
@@ -1123,15 +1124,15 @@ enum lfsr_tag {
// struct tags
LFSR_TAG_STRUCT = 0x0300,
LFSR_TAG_DATA = 0x0300,
LFSR_TAG_BLOCK = 0x0304,
LFSR_TAG_BSHRUB = 0x0308,
LFSR_TAG_BTREE = 0x030c,
LFSR_TAG_MROOT = 0x0311,
LFSR_TAG_MDIR = 0x0315,
LFSR_TAG_MTREE = 0x031c,
LFSR_TAG_DID = 0x0320,
LFSR_TAG_BRANCH = 0x032c,
LFSR_TAG_BRANCH = 0x0300,
LFSR_TAG_DATA = 0x0304,
LFSR_TAG_BLOCK = 0x0308,
LFSR_TAG_DID = 0x0314,
LFSR_TAG_BSHRUB = 0x0318,
LFSR_TAG_BTREE = 0x031c,
LFSR_TAG_MROOT = 0x0321,
LFSR_TAG_MDIR = 0x0325,
LFSR_TAG_MTREE = 0x032c,
// user/sys attributes
LFSR_TAG_ATTR = 0x0400,
@@ -3508,8 +3509,8 @@ static int lfsr_rbyd_appendrattr_(lfs_t *lfs, lfsr_rbyd_t *rbyd,
// leb128?
} else if (rattr.count >= 0
&& (rattr.tag == LFSR_TAG_NAMELIMIT
|| rattr.tag == LFSR_TAG_FILELIMIT
&& (rattr.tag == LFSR_TAG_FILELIMIT
|| rattr.tag == LFSR_TAG_NAMELIMIT
|| rattr.tag == LFSR_TAG_DID)) {
// leb128s should not exceed 31-bits
LFS_ASSERT(rattr.u.leb128 <= 0x7fffffff);
@@ -13818,32 +13819,6 @@ static int lfsr_mountmroot(lfs_t *lfs, const lfsr_mdir_t *mroot) {
lfs->block_count = geometry.block_count;
// read the name limit
lfs_size_t name_limit = 0xff;
err = lfsr_mdir_lookup(lfs, mroot, LFSR_TAG_NAMELIMIT,
NULL, &data);
if (err && err != LFS_ERR_NOENT) {
return err;
}
if (err != LFS_ERR_NOENT) {
err = lfsr_data_readleb128(lfs, &data, &name_limit);
if (err && err != LFS_ERR_CORRUPT) {
return err;
}
if (err == LFS_ERR_CORRUPT) {
name_limit = -1;
}
}
if (name_limit > lfs->name_limit) {
LFS_ERROR("Incompatible name limit %"PRId32" (> %"PRId32")",
name_limit,
lfs->name_limit);
return LFS_ERR_NOTSUP;
}
lfs->name_limit = name_limit;
// read the file limit
lfs_off_t file_limit = 0x7fffffff;
err = lfsr_mdir_lookup(lfs, mroot, LFSR_TAG_FILELIMIT,
@@ -13870,9 +13845,35 @@ static int lfsr_mountmroot(lfs_t *lfs, const lfsr_mdir_t *mroot) {
lfs->file_limit = file_limit;
// read the name limit
lfs_size_t name_limit = 0xff;
err = lfsr_mdir_lookup(lfs, mroot, LFSR_TAG_NAMELIMIT,
NULL, &data);
if (err && err != LFS_ERR_NOENT) {
return err;
}
if (err != LFS_ERR_NOENT) {
err = lfsr_data_readleb128(lfs, &data, &name_limit);
if (err && err != LFS_ERR_CORRUPT) {
return err;
}
if (err == LFS_ERR_CORRUPT) {
name_limit = -1;
}
}
if (name_limit > lfs->name_limit) {
LFS_ERROR("Incompatible name limit %"PRId32" (> %"PRId32")",
name_limit,
lfs->name_limit);
return LFS_ERR_NOTSUP;
}
lfs->name_limit = name_limit;
// check for unknown configs
lfsr_tag_t tag;
err = lfsr_mdir_lookupnext(lfs, mroot, LFSR_TAG_FILELIMIT+1,
err = lfsr_mdir_lookupnext(lfs, mroot, LFSR_TAG_UNKNOWNCONFIG,
&tag, NULL);
if (err && err != LFS_ERR_NOENT) {
return err;