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ckparity: Limited post-readtag parity checking to just data

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No reason to keep checking the parity of the tag after we've decoded
things.

Code changes minimal:

                    code          stack
  default before:  36416           2616
  default after:   36416 (+0.0%)   2616 (+0.0%)

  ckparity before: 37996           3040
  ckparity after:  38000 (+0.0%)   3040 (+0.0%)
This commit is contained in:
Christopher Haster
2024-08-20 12:04:13 -05:00
parent e492af7e61
commit 8194fb9602
1 changed files with 13 additions and 11 deletions
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lfs.c
+13 -11
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@@ -1716,13 +1716,13 @@ static lfs_ssize_t lfsr_bd_readtag(lfs_t *lfs,
#ifdef LFS_CKCKSUMS
// if we're checking checksums and not already calculating a
// checksum, we first need to checksum any prefixed data
uint32_t cksum__ = 0;
uint32_t cksum_ = 0;
if (lfsr_m_isckcksums(lfs->flags) && !cksum) {
int err = lfsr_bd_ckprefix(lfs, block, off, hint,
// the actual parity doesn't really matter here
LFSR_CK_PARITY_(off, 0, 0),
&hint,
&cksum__);
&cksum_);
if (err) {
return err;
}
@@ -1802,17 +1802,18 @@ static lfs_ssize_t lfsr_bd_readtag(lfs_t *lfs,
// the data will stick around in the cache
if (lfsr_m_isckparity(lfs->flags) && !cksum) {
// checksum the tag, including our valid bit
uint32_t cksum_ = lfs_crc32c(0, tag_buf, d);
uint32_t cksum__ = lfs_crc32c(0, tag_buf, d);
// checksum the data, if we have any
lfs_size_t hint_ = hint - lfs_min(d, hint);
lfs_size_t d_ = d;
uint32_t cksum___ = cksum__;
if (!lfsr_tag_isalt(tag)) {
err = lfsr_bd_cksum(lfs,
// make sure hint includes our pesky parity byte
block, off+d_, lfs_max(hint_, size+1),
size,
&cksum_);
&cksum___);
if (err) {
return err;
}
@@ -1834,17 +1835,18 @@ static lfs_ssize_t lfsr_bd_readtag(lfs_t *lfs,
}
// does parity match?
if (lfs_parity(cksum_) != parity) {
if (lfs_parity(cksum___) != parity) {
LFS_ERROR("Found ckparity mismatch "
"0x%"PRIx32".%"PRIx32" %"PRId32", "
"parity %01"PRIx32" (!= %01"PRIx32")",
block, off, d_,
lfs_parity(cksum_), parity);
lfs_parity(cksum___), parity);
return LFS_ERR_CORRUPT;
}
// return the parity of just the data;
if (parity_) {
*parity_ = parity;
*parity_ = parity ^ lfs_parity(cksum__);
}
}
#endif
@@ -1856,16 +1858,16 @@ static lfs_ssize_t lfsr_bd_readtag(lfs_t *lfs,
// this uses the rbyd's checksum to check things
if (lfsr_m_isckcksums(lfs->flags) && !cksum) {
// exclude valid bit from checksum
cksum__ ^= tag_buf[0] & 0x00000080;
cksum_ ^= tag_buf[0] & 0x00000080;
// calculate checksum
cksum__ = lfs_crc32c(cksum__, tag_buf, d);
cksum_ = lfs_crc32c(cksum_, tag_buf, d);
err = lfsr_bd_cksuffix(lfs, block, off+d, hint,
// the actual parity doesn't really matter here
LFSR_CK_PARITY_(off,
d + ((!lfsr_tag_isalt(tag)) ? size : 0),
0),
cksum__);
cksum_);
if (err) {
return err;
}
@@ -3271,7 +3273,7 @@ static int lfsr_rbyd_lookupnext(lfs_t *lfs, const lfsr_rbyd_t *rbyd,
if (data_) {
*data_ = LFSR_DATA_DISKPARITY(
rbyd->blocks[0], branch + d, jump,
branch, d + jump,
branch + d, jump,
// we don't really care about the parity if
// we're not checking it
LFS_IFDEF_CKPARITY(parity, false));