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Implicitly set the rm-bit in generic grow tags

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Our rbyds support changing the weight of a tag without knowing the
actual tag. This is useful for btrees, which always make weight changes
without knowing if the leading tag is a name or a branch (it depends on
the type of btree).

But to make this work, it needs the rm-bit to be set. This is because
internally the rm-bit indicates we don't want to write-out a tag. Which
we don't for grow tags, because, well, they're not real tags.

Previously this was done by putting LFSR_TAG_GROW(RM) everywhere a
generic grow as needed, but since this is so common we might as well
just set the rm-bit in LFSR_TAG_GROW.

Note that LFSR_TAG_GROW(tag) (the macro) does not set the rm-bit.

This makes the code a bit more readable at the risk of an unintuitive
relationship between LFSR_TAG_GROW and LFSR_TAG_GROW(tag).
This commit is contained in:
Christopher Haster
2023-08-18 13:33:04 -05:00
parent 6088180076
commit bacd09a673
3 changed files with 12 additions and 11 deletions
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lfs.c
+7 -6
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@@ -619,7 +619,7 @@ enum lfsr_tag_type {
// some tag modifiers
// in-device only
LFSR_TAG_WIDE = 0x4000,
LFSR_TAG_GROW = 0x2000,
LFSR_TAG_GROW = 0x3000, // note generic grows need the rm-bit
LFSR_TAG_RM = 0x1000,
// in-device only
@@ -632,8 +632,9 @@ enum lfsr_tag_type {
// some tag modifiers
#define LFSR_TAG_WIDE(tag) (LFSR_TAG_WIDE | LFSR_TAG_##tag)
#define LFSR_TAG_GROW(tag) (LFSR_TAG_GROW | LFSR_TAG_##tag)
#define LFSR_TAG_RM(tag) (LFSR_TAG_RM | LFSR_TAG_##tag)
// if we're growing an explict tag, we don't need the rm-bit
#define LFSR_TAG_GROW(tag) ((LFSR_TAG_GROW & ~LFSR_TAG_RM) | LFSR_TAG_##tag)
#define LFSR_TAG_RM(tag) (LFSR_TAG_RM | LFSR_TAG_##tag)
// some other tag encodings with their own subfields
#define LFSR_TAG_ALT(d, c, key) \
@@ -4090,7 +4091,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
bid+rid, BRANCH, 0,
BUF(scratch_buf, scratch_dsize));
scratch_attrs[1] = LFSR_ATTR(
bid+rid, GROW(RM), -rbyd.weight + rbyd_.weight,
bid+rid, GROW, -rbyd.weight + rbyd_.weight,
NULL);
attrs = scratch_attrs;
attr_count = 2;
@@ -4228,7 +4229,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
bid+rid, BRANCH, 0,
BUF(scratch1_buf, scratch1_dsize));
scratch_attrs[1] = LFSR_ATTR(
bid+rid, GROW(RM), -rbyd.weight + rbyd_.weight,
bid+rid, GROW, -rbyd.weight + rbyd_.weight,
NULL);
}
scratch_attrs[2] = LFSR_ATTR(
@@ -4333,7 +4334,7 @@ static int lfsr_btree_commit(lfs_t *lfs, lfsr_btree_t *btree,
bid+rid, BRANCH, 0,
BUF(scratch_buf, scratch_dsize));
scratch_attrs[2] = LFSR_ATTR(
bid+rid, GROW(RM), -rbyd.weight + rbyd_.weight,
bid+rid, GROW, -rbyd.weight + rbyd_.weight,
NULL);
attrs = scratch_attrs;
attr_count = 3;