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Fixed incorrect condition preventing left fragment coalescing

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The condition for checking if the left fragment could be coalesced was
wrong, preventing a common coalescing chance in linear rewrites, and
leaving a weird 1-flush-sized alignment issue in the fragments:

Was:        lfsr_data_size(&bptr.data) < lfs->cfg->fragment_size
Should be:  fragment_end - (bid-(weight-1)) <= lfs->cfg->fragment_size

This was correct for the right fragment coalescing, not sure how the
left ended up messed up.

(Actually I do know why, the math here is dense, complex, and subtle,
a nasty combo.)
This commit is contained in:
Christopher Haster
2024-01-02 15:23:08 -06:00
parent b15940461d
commit f14d06b22b
1 changed files with 5 additions and 8 deletions
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lfs.c
+5 -8
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@@ -10380,10 +10380,9 @@ static int lfsr_ftree_flush(lfs_t *lfs, lfsr_ftree_t *ftree,
} }
// can we coalesce? // can we coalesce?
if (bid-(weight-1) + lfsr_data_size(&bptr.data) if (bid-(weight-1) + lfsr_data_size(&bptr.data) >= fragment_start
>= fragment_start && fragment_end - (bid-(weight-1))
&& lfsr_data_size(&bptr.data) <= lfs->cfg->fragment_size) {
< lfs->cfg->fragment_size) {
// coalesce, but truncate to our fragment size // coalesce, but truncate to our fragment size
// TODO this is a bit of a hacky way to prepend data... // TODO this is a bit of a hacky way to prepend data...
LFS_ASSERT(data_count == 1); LFS_ASSERT(data_count == 1);
@@ -10405,8 +10404,7 @@ static int lfsr_ftree_flush(lfs_t *lfs, lfsr_ftree_t *ftree,
// note this may the same as our left sibling // note this may the same as our left sibling
if (fragment_end < lfsr_ftree_size(ftree) if (fragment_end < lfsr_ftree_size(ftree)
// don't bother to lookup right if fragment is already full // don't bother to lookup right if fragment is already full
&& fragment_end - fragment_start && fragment_end - fragment_start < lfs->cfg->fragment_size) {
< lfs->cfg->fragment_size) {
lfsr_bid_t bid; lfsr_bid_t bid;
lfsr_tag_t tag; lfsr_tag_t tag;
lfsr_bid_t weight; lfsr_bid_t weight;
@@ -10420,8 +10418,7 @@ static int lfsr_ftree_flush(lfs_t *lfs, lfsr_ftree_t *ftree,
} }
// can we coalesce? // can we coalesce?
if (fragment_end < bid-(weight-1) if (fragment_end < bid-(weight-1) + lfsr_data_size(&bptr.data)
+ lfsr_data_size(&bptr.data)
&& bid-(weight-1) + lfsr_data_size(&bptr.data) && bid-(weight-1) + lfsr_data_size(&bptr.data)
- fragment_start - fragment_start
<= lfs->cfg->fragment_size) { <= lfs->cfg->fragment_size) {