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Garbage collect unused links in /nix/store/.links

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Incremental optimisation requires creating links in /nix/store/.links
to all files in the store.  However, this means that if we delete a
store path, no files are actually deleted because links in
/nix/store/.links still exists.  So we need to check /nix/store/.links
for files with a link count of 1 and delete them.
This commit is contained in:
Eelco Dolstra 2012-07-23 15:48:30 -04:00
parent 6193105710
commit 680ab6f83d
2 changed files with 39 additions and 0 deletions
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37
src/libstore/gc.cc
View file

@ -436,6 +436,8 @@ bool LocalStore::tryToDelete(GCState & state, const Path & path)
{
checkInterrupt();
if (path == linksDir) return true;
struct stat st;
if (lstat(path.c_str(), &st)) {
if (errno == ENOENT) return true;
@ -569,6 +571,37 @@ bool LocalStore::tryToDelete(GCState & state, const Path & path)
}
/* 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
might see a link count of 1 just before optimisePath() increases
the link count. */
void LocalStore::removeUnusedLinks()
{
AutoCloseDir dir = opendir(linksDir.c_str());
if (!dir) throw SysError(format("opening directory `%1%'") % linksDir);
struct dirent * dirent;
while (errno = 0, dirent = readdir(dir)) {
checkInterrupt();
string name = dirent->d_name;
if (name == "." || name == "..") continue;
Path path = linksDir + "/" + name;
struct stat st;
if (lstat(path.c_str(), &st) == -1)
throw SysError(format("statting `%1%'") % path);
if (st.st_nlink != 1) continue;
printMsg(lvlTalkative, format("deleting unused link `%1%'") % path);
if (unlink(path.c_str()) == -1)
throw SysError(format("deleting `%1%'") % path);
}
}
void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
{
GCState state(results);
@ -682,6 +715,10 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
released. */
foreach (PathSet::iterator, i, state.invalidated)
deleteGarbage(state, *i);
/* Clean up the links directory. */
printMsg(lvlError, format("deleting unused links..."));
removeUnusedLinks();
}

2
src/libstore/local-store.hh
View file

@ -264,6 +264,8 @@ private:
int openGCLock(LockType lockType);
void removeUnusedLinks();
void startSubstituter(const Path & substituter,
RunningSubstituter & runningSubstituter);