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Passing down the original edata on the expand path.

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Instead of passing down the new_addr, pass down the active edata which allows us
to always use a neighbor-acquiring semantic.  In other words, this tells us both
the original edata and neighbor address.  With this change, only neighbors of a
"known" edata can be acquired, i.e. acquiring an edata based on an arbitrary
address isn't possible anymore.
This commit is contained in:
Qi Wang
2021-03-11 00:21:47 -08:00
committed by Qi Wang
parent 1784939688
commit 49b7d7f0a4
6 changed files with 116 additions and 101 deletions
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84
src/emap.c
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@@ -70,7 +70,8 @@ edata_neighbor_head_state_mergeable(bool edata_is_head,
static inline bool
edata_can_acquire_neighbor(edata_t *edata, rtree_contents_t contents,
extent_pai_t pai, extent_state_t expected_state, bool forward) {
extent_pai_t pai, extent_state_t expected_state, bool forward,
bool expanding) {
edata_t *neighbor = contents.edata;
if (neighbor == NULL) {
return false;
@@ -87,8 +88,8 @@ edata_can_acquire_neighbor(edata_t *edata, rtree_contents_t contents,
return false;
}
/* From this point, it's safe to access *neighbor. */
if (edata_committed_get(edata) !=
edata_committed_get(neighbor)) {
if (!expanding && (edata_committed_get(edata) !=
edata_committed_get(neighbor))) {
/*
* Some platforms (e.g. Windows) require an explicit
* commit step (and writing to uncomitted memory is not
@@ -125,47 +126,13 @@ edata_can_acquire_neighbor(edata_t *edata, rtree_contents_t contents,
return true;
}
/* Will be removed in the next commit. */
edata_t *
emap_try_acquire_edata(tsdn_t *tsdn, emap_t *emap, void *addr,
extent_state_t expected_state, bool allow_head_extent) {
EMAP_DECLARE_RTREE_CTX;
rtree_leaf_elm_t *elm = rtree_leaf_elm_lookup(tsdn, &emap->rtree,
rtree_ctx, (uintptr_t)addr, false, false);
if (elm == NULL) {
return NULL;
}
rtree_contents_t contents = rtree_leaf_elm_read(tsdn, &emap->rtree, elm,
/* dependent */ true);
if (!allow_head_extent && contents.metadata.is_head) {
/* !allow_head_extent indicates the expanding path. */
return NULL;
}
edata_t *edata = contents.edata;
if (edata == NULL || contents.metadata.state != expected_state) {
return NULL;
}
assert(edata_state_get(edata) == expected_state);
emap_update_edata_state(tsdn, emap, edata, extent_state_updating);
return edata;
}
void
emap_release_edata(tsdn_t *tsdn, emap_t *emap, edata_t *edata,
extent_state_t new_state) {
assert(emap_edata_in_transition(tsdn, emap, edata));
assert(emap_edata_is_acquired(tsdn, emap, edata));
emap_update_edata_state(tsdn, emap, edata, new_state);
}
edata_t *
emap_try_acquire_edata_neighbor(tsdn_t *tsdn, emap_t *emap, edata_t *edata,
extent_pai_t pai, extent_state_t expected_state, bool forward) {
static inline edata_t *
emap_try_acquire_edata_neighbor_impl(tsdn_t *tsdn, emap_t *emap, edata_t *edata,
extent_pai_t pai, extent_state_t expected_state, bool forward,
bool expanding) {
witness_assert_positive_depth_to_rank(tsdn_witness_tsdp_get(tsdn),
WITNESS_RANK_CORE);
assert(!expanding || forward);
assert(!edata_state_in_transition(expected_state));
assert(expected_state == extent_state_dirty ||
expected_state == extent_state_muzzy ||
@@ -196,18 +163,47 @@ emap_try_acquire_edata_neighbor(tsdn_t *tsdn, emap_t *emap, edata_t *edata,
rtree_contents_t neighbor_contents = rtree_leaf_elm_read(tsdn,
&emap->rtree, elm, /* dependent */ true);
if (!edata_can_acquire_neighbor(edata, neighbor_contents, pai,
expected_state, forward)) {
expected_state, forward, expanding)) {
return NULL;
}
/* From this point, the neighbor edata can be safely acquired. */
edata_t *neighbor = neighbor_contents.edata;
assert(edata_state_get(neighbor) == expected_state);
emap_update_edata_state(tsdn, emap, neighbor, extent_state_merging);
extent_assert_can_coalesce(edata, neighbor);
if (expanding) {
extent_assert_can_expand(edata, neighbor);
} else {
extent_assert_can_coalesce(edata, neighbor);
}
return neighbor;
}
edata_t *
emap_try_acquire_edata_neighbor(tsdn_t *tsdn, emap_t *emap, edata_t *edata,
extent_pai_t pai, extent_state_t expected_state, bool forward) {
return emap_try_acquire_edata_neighbor_impl(tsdn, emap, edata, pai,
expected_state, forward, /* expand */ false);
}
edata_t *
emap_try_acquire_edata_neighbor_expand(tsdn_t *tsdn, emap_t *emap,
edata_t *edata, extent_pai_t pai, extent_state_t expected_state) {
/* Try expanding forward. */
return emap_try_acquire_edata_neighbor_impl(tsdn, emap, edata, pai,
expected_state, /* forward */ true, /* expand */ true);
}
void
emap_release_edata(tsdn_t *tsdn, emap_t *emap, edata_t *edata,
extent_state_t new_state) {
assert(emap_edata_in_transition(tsdn, emap, edata));
assert(emap_edata_is_acquired(tsdn, emap, edata));
emap_update_edata_state(tsdn, emap, edata, new_state);
}
static bool
emap_rtree_leaf_elms_lookup(tsdn_t *tsdn, emap_t *emap, rtree_ctx_t *rtree_ctx,
const edata_t *edata, bool dependent, bool init_missing,