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Code Activity

* Move root finding from nix-collect-garbage' to nix-store --gc'.

Browse source 
This was necessary becase root finding must be done after
  acquisition of the global GC lock.

  This makes `nix-collect-garbage' obsolete; it is now just a wrapper
  around `nix-store --gc'.

* Automatically remove stale GC roots (i.e., indirect GC roots that
  point to non-existent paths).
This commit is contained in:
Eelco Dolstra 2005-02-01 15:05:32 +00:00
parent 630ae0c9d7
commit 65b6c8ab4c
4 changed files with 75 additions and 111 deletions
Download patch file Download diff file Expand all files Collapse all files

59
src/libstore/gc.cc
View file

@ -26,7 +26,9 @@ static int openGCLock(LockType lockType)
{
Path fnGCLock = (format("%1%/%2%")
% nixStateDir % gcLockName).str();
debug(format("acquiring global GC lock `%1%'") % fnGCLock);
AutoCloseFD fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT, 0600);
if (fdGCLock == -1)
throw SysError(format("opening global GC lock `%1%'") % fnGCLock);
@ -234,6 +236,46 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
}
static void findRoots(const Path & path, bool recurseSymlinks,
PathSet & roots)
{
struct stat st;
if (lstat(path.c_str(), &st) == -1)
throw SysError(format("statting `%1%'") % path);
printMsg(lvlVomit, format("looking at `%1%'") % path);
if (S_ISDIR(st.st_mode)) {
Strings names = readDirectory(path);
for (Strings::iterator i = names.begin(); i != names.end(); ++i)
findRoots(path + "/" + *i, recurseSymlinks, roots);
}
else if (S_ISLNK(st.st_mode)) {
string target = readLink(path);
Path target2 = absPath(target, dirOf(path));
if (isStorePath(target2)) {
debug(format("found root `%1%' in `%2%'")
% target2 % path);
roots.insert(target2);
}
else if (recurseSymlinks) {
if (pathExists(target2))
findRoots(target2, false, roots);
else {
printMsg(lvlInfo, format("removing stale link from `%1%' to `%2%'") % path % target2);
/* Note that we only delete when recursing, i.e., when
we are still in the `gcroots' tree. We never
delete stuff outside that tree. */
unlink(path.c_str());
}
}
}
}
static void dfsVisit(const PathSet & paths, const Path & path,
PathSet & visited, Paths & sorted)
{
@ -265,8 +307,7 @@ static Paths topoSort(const PathSet & paths)
}
void collectGarbage(const PathSet & roots, GCAction action,
PathSet & result)
void collectGarbage(GCAction action, PathSet & result)
{
result.clear();
@ -275,8 +316,16 @@ void collectGarbage(const PathSet & roots, GCAction action,
b) Processes from creating new temporary root files. */
AutoCloseFD fdGCLock = openGCLock(ltWrite);
/* !!! Find the roots here, after we've grabbed the GC lock, since
the set of permanent roots cannot increase now. */
/* Find the roots. Since we've grabbed the GC lock, the set of
permanent roots cannot increase now. */
Path rootsDir = canonPath((format("%1%/%2%") % nixStateDir % gcRootsDir).str());
PathSet roots;
findRoots(rootsDir, true, roots);
if (action == gcReturnRoots) {
result = roots;
return;
}
/* Determine the live paths which is just the closure of the
roots under the `references' relation. */