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Make the canReachRoots() traversal non-recursive

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This commit is contained in:
Eelco Dolstra 2021-10-14 12:31:21 +02:00
parent 09b14ea97a
commit eab934cb2a
3 changed files with 115 additions and 111 deletions
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210
src/libstore/gc.cc
View file

@ -499,75 +499,6 @@ void LocalStore::deleteFromStore(GCState & state, std::string_view baseName)
}
bool LocalStore::canReachRoot(
GCState & state,
StorePathSet & visited,
const StorePath & path)
{
checkInterrupt();
//Activity act(*logger, lvlDebug, format("considering whether to delete '%1%'") % path);
if (state.options.action == GCOptions::gcDeleteSpecific
&& !state.options.pathsToDelete.count(path))
return true;
if (!visited.insert(path).second) return false;
if (state.alive.count(path)) return true;
if (state.dead.count(path)) return false;
if (state.roots.count(path)) {
debug("cannot delete '%s' because it's a root", printStorePath(path));
state.alive.insert(path);
return true;
}
if (isValidPath(path)) {
StorePathSet incoming;
/* Don't delete this path if any of its referrers are alive. */
queryReferrers(path, incoming);
/* If keep-derivations is set and this is a derivation, then
don't delete the derivation if any of the outputs are
alive. */
if (state.gcKeepDerivations && path.isDerivation()) {
for (auto & [name, maybeOutPath] : queryPartialDerivationOutputMap(path))
if (maybeOutPath &&
isValidPath(*maybeOutPath) &&
queryPathInfo(*maybeOutPath)->deriver == path)
incoming.insert(*maybeOutPath);
}
/* If keep-outputs is set, then don't delete this path if
there are derivers of this path that are not garbage. */
if (state.gcKeepOutputs) {
auto derivers = queryValidDerivers(path);
for (auto & i : derivers)
incoming.insert(i);
}
for (auto & i : incoming)
if (i != path && canReachRoot(state, visited, i)) {
state.alive.insert(path);
return true;
}
}
{
auto hashPart = std::string(path.hashPart());
auto shared(state.shared.lock());
if (shared->tempRoots.count(hashPart))
return true;
shared->pending = hashPart;
}
return false;
}
/* Unlink all files in /nix/store/.links that have a link count of 1,
which indicates that there are no other links and so they can be
safely deleted. FIXME: race condition with optimisePath(): we
@ -746,28 +677,115 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
state.roots.insert(root.first);
}
/* Now either delete all garbage paths, or just the specified
paths (for gcDeleteSpecific). */
/* Helper function that visits all paths reachable from `start`
via the referrers edges and optionally derivers and derivation
output edges. If any of those paths is a root, then we cannot
delete this path. */
auto deleteReferrersClosure = [&](const StorePath & start) {
StorePathSet visited;
std::queue<StorePath> todo;
/* Wake up any GC client waiting for deletion of the paths in
'visited' to finish. */
Finally releasePending([&]() {
auto shared(state.shared.lock());
shared->pending.reset();
state.wakeup.notify_all();
});
auto enqueue = [&](const StorePath & path) {
if (visited.insert(path).second)
todo.push(path);
};
enqueue(start);
while (auto path = pop(todo)) {
checkInterrupt();
/* Bail out if we've previously discovered that this path
is alive. */
if (state.alive.count(*path)) {
state.alive.insert(start);
return;
}
/* If we've previously deleted this path, we don't have to
handle it again. */
if (state.dead.count(*path)) continue;
/* If this is a root, bail out. */
if (state.roots.count(*path)) {
debug("cannot delete '%s' because it's a root", printStorePath(*path));
state.alive.insert(*path);
state.alive.insert(start);
return;
}
if (state.options.action == GCOptions::gcDeleteSpecific
&& !state.options.pathsToDelete.count(*path))
return;
{
auto hashPart = std::string(path->hashPart());
auto shared(state.shared.lock());
if (shared->tempRoots.count(hashPart)) {
debug("cannot delete '%s' because it's a temporary root", printStorePath(*path));
state.alive.insert(*path);
state.alive.insert(start);
return;
}
shared->pending = hashPart;
}
if (isValidPath(*path)) {
/* Visit the referrers of this path. */
StorePathSet referrers;
queryReferrers(*path, referrers);
for (auto & p : referrers)
enqueue(p);
/* If keep-derivations is set and this is a
derivation, then visit the derivation outputs. */
if (state.gcKeepDerivations && path->isDerivation()) {
for (auto & [name, maybeOutPath] : queryPartialDerivationOutputMap(*path))
if (maybeOutPath &&
isValidPath(*maybeOutPath) &&
queryPathInfo(*maybeOutPath)->deriver == *path)
enqueue(*maybeOutPath);
}
/* If keep-outputs is set, then visit the derivers. */
if (state.gcKeepOutputs) {
auto derivers = queryValidDerivers(*path);
for (auto & i : derivers)
enqueue(i);
}
}
}
for (auto & path : topoSortPaths(visited)) {
if (!state.dead.insert(path).second) continue;
if (state.shouldDelete) {
invalidatePathChecked(path);
deleteFromStore(state, path.to_string());
}
}
};
/* Either delete all garbage paths, or just the specified
paths (for gcDeleteSpecific). */
if (options.action == GCOptions::gcDeleteSpecific) {
for (auto & i : options.pathsToDelete) {
StorePathSet visited;
if (canReachRoot(state, visited, i))
deleteReferrersClosure(i);
if (!state.dead.count(i))
throw Error(
"cannot delete path '%1%' since it is still alive. "
"Cannot delete path '%1%' since it is still alive. "
"To find out why, use: "
"nix-store --query --roots",
printStorePath(i));
auto sorted = topoSortPaths(visited);
for (auto & path : sorted) {
if (state.dead.count(path)) continue;
invalidatePathChecked(path);
deleteFromStore(state, path.to_string());
state.dead.insert(path);
}
}
} else if (options.maxFreed > 0) {
@ -792,29 +810,9 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
string name = dirent->d_name;
if (name == "." || name == ".." || name == linksName) continue;
if (auto storePath = maybeParseStorePath(storeDir + "/" + name)) {
StorePathSet visited;
/* Wake up any GC client waiting for deletion of
the paths in 'visited' to finish. */
Finally releasePending([&]() {
auto shared(state.shared.lock());
shared->pending.reset();
state.wakeup.notify_all();
});
if (!canReachRoot(state, visited, *storePath)) {
auto sorted = topoSortPaths(visited);
for (auto & path : sorted) {
if (state.dead.count(path)) continue;
if (state.shouldDelete) {
invalidatePathChecked(path);
deleteFromStore(state, path.to_string());
}
state.dead.insert(path);
}
}
} else
if (auto storePath = maybeParseStorePath(storeDir + "/" + name))
deleteReferrersClosure(*storePath);
else
deleteFromStore(state, name);
}

5
src/libstore/local-store.hh
View file

@ -240,11 +240,6 @@ private:
struct GCState;
bool canReachRoot(
GCState & state,
StorePathSet & visited,
const StorePath & path);
void deleteFromStore(GCState & state, std::string_view baseName);
void findRoots(const Path & path, unsigned char type, Roots & roots);

11
src/libutil/util.hh
View file

@ -523,6 +523,17 @@ std::optional<typename T::value_type> remove_begin(T & c)
}
/* Remove and return the first item from a container. */
template <class T>
std::optional<typename T::value_type> pop(T & c)
{
if (c.empty()) return {};
auto v = std::move(c.front());
c.pop();
return v;
}
template<typename T>
class Callback;