forked from lix-project/lix
753 lines
24 KiB
C++
753 lines
24 KiB
C++
#include "globals.hh"
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#include "misc.hh"
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#include "local-store.hh"
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#include <boost/shared_ptr.hpp>
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#include <functional>
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#include <queue>
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#include <algorithm>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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namespace nix {
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static string gcLockName = "gc.lock";
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static string tempRootsDir = "temproots";
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static string gcRootsDir = "gcroots";
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static const int defaultGcLevel = 1000;
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/* Acquire the global GC lock. This is used to prevent new Nix
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processes from starting after the temporary root files have been
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read. To be precise: when they try to create a new temporary root
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file, they will block until the garbage collector has finished /
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yielded the GC lock. */
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int LocalStore::openGCLock(LockType lockType)
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{
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Path fnGCLock = (format("%1%/%2%")
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% settings.nixStateDir % gcLockName).str();
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debug(format("acquiring global GC lock `%1%'") % fnGCLock);
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AutoCloseFD fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT, 0600);
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if (fdGCLock == -1)
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throw SysError(format("opening global GC lock `%1%'") % fnGCLock);
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closeOnExec(fdGCLock);
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if (!lockFile(fdGCLock, lockType, false)) {
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printMsg(lvlError, format("waiting for the big garbage collector lock..."));
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lockFile(fdGCLock, lockType, true);
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}
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/* !!! Restrict read permission on the GC root. Otherwise any
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process that can open the file for reading can DoS the
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collector. */
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return fdGCLock.borrow();
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}
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void createSymlink(const Path & link, const Path & target)
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{
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/* Create directories up to `gcRoot'. */
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createDirs(dirOf(link));
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/* Create the new symlink. */
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Path tempLink = (format("%1%.tmp-%2%-%3%")
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% link % getpid() % rand()).str();
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if (symlink(target.c_str(), tempLink.c_str()) == -1)
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throw SysError(format("symlinking `%1%' to `%2%'")
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% tempLink % target);
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/* Atomically replace the old one. */
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if (rename(tempLink.c_str(), link.c_str()) == -1)
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throw SysError(format("cannot rename `%1%' to `%2%'")
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% tempLink % link);
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}
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void LocalStore::syncWithGC()
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{
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AutoCloseFD fdGCLock = openGCLock(ltRead);
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}
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void LocalStore::addIndirectRoot(const Path & path)
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{
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string hash = printHash32(hashString(htSHA1, path));
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Path realRoot = canonPath((format("%1%/%2%/auto/%3%")
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% settings.nixStateDir % gcRootsDir % hash).str());
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createSymlink(realRoot, path);
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}
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Path addPermRoot(StoreAPI & store, const Path & _storePath,
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const Path & _gcRoot, bool indirect, bool allowOutsideRootsDir)
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{
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Path storePath(canonPath(_storePath));
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Path gcRoot(canonPath(_gcRoot));
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assertStorePath(storePath);
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if (isInStore(gcRoot))
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throw Error(format(
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"creating a garbage collector root (%1%) in the Nix store is forbidden "
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"(are you running nix-build inside the store?)") % gcRoot);
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if (indirect) {
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/* Don't clobber the the link if it already exists and doesn't
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point to the Nix store. */
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if (pathExists(gcRoot) && (!isLink(gcRoot) || !isInStore(readLink(gcRoot))))
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throw Error(format("cannot create symlink `%1%'; already exists") % gcRoot);
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createSymlink(gcRoot, storePath);
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store.addIndirectRoot(gcRoot);
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}
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else {
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if (!allowOutsideRootsDir) {
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Path rootsDir = canonPath((format("%1%/%2%") % settings.nixStateDir % gcRootsDir).str());
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if (string(gcRoot, 0, rootsDir.size() + 1) != rootsDir + "/")
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throw Error(format(
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"path `%1%' is not a valid garbage collector root; "
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"it's not in the directory `%2%'")
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% gcRoot % rootsDir);
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}
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createSymlink(gcRoot, storePath);
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}
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/* Check that the root can be found by the garbage collector.
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!!! This can be very slow on machines that have many roots.
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Instead of reading all the roots, it would be more efficient to
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check if the root is in a directory in or linked from the
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gcroots directory. */
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if (settings.checkRootReachability) {
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Roots roots = store.findRoots();
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if (roots.find(gcRoot) == roots.end())
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printMsg(lvlError,
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format(
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"warning: `%1%' is not in a directory where the garbage collector looks for roots; "
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"therefore, `%2%' might be removed by the garbage collector")
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% gcRoot % storePath);
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}
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/* Grab the global GC root, causing us to block while a GC is in
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progress. This prevents the set of permanent roots from
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increasing while a GC is in progress. */
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store.syncWithGC();
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return gcRoot;
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}
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/* The file to which we write our temporary roots. */
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static Path fnTempRoots;
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static AutoCloseFD fdTempRoots;
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void LocalStore::addTempRoot(const Path & path)
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{
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/* Create the temporary roots file for this process. */
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if (fdTempRoots == -1) {
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while (1) {
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Path dir = (format("%1%/%2%") % settings.nixStateDir % tempRootsDir).str();
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createDirs(dir);
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fnTempRoots = (format("%1%/%2%")
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% dir % getpid()).str();
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AutoCloseFD fdGCLock = openGCLock(ltRead);
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if (pathExists(fnTempRoots))
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/* It *must* be stale, since there can be no two
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processes with the same pid. */
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unlink(fnTempRoots.c_str());
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fdTempRoots = openLockFile(fnTempRoots, true);
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fdGCLock.close();
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debug(format("acquiring read lock on `%1%'") % fnTempRoots);
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lockFile(fdTempRoots, ltRead, true);
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/* Check whether the garbage collector didn't get in our
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way. */
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struct stat st;
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if (fstat(fdTempRoots, &st) == -1)
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throw SysError(format("statting `%1%'") % fnTempRoots);
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if (st.st_size == 0) break;
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/* The garbage collector deleted this file before we could
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get a lock. (It won't delete the file after we get a
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lock.) Try again. */
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}
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}
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/* Upgrade the lock to a write lock. This will cause us to block
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if the garbage collector is holding our lock. */
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debug(format("acquiring write lock on `%1%'") % fnTempRoots);
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lockFile(fdTempRoots, ltWrite, true);
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string s = path + '\0';
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writeFull(fdTempRoots, (const unsigned char *) s.data(), s.size());
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/* Downgrade to a read lock. */
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debug(format("downgrading to read lock on `%1%'") % fnTempRoots);
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lockFile(fdTempRoots, ltRead, true);
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}
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void removeTempRoots()
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{
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if (fdTempRoots != -1) {
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fdTempRoots.close();
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unlink(fnTempRoots.c_str());
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}
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}
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/* Automatically clean up the temporary roots file when we exit. */
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struct RemoveTempRoots
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{
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~RemoveTempRoots()
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{
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removeTempRoots();
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}
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};
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static RemoveTempRoots autoRemoveTempRoots __attribute__((unused));
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typedef boost::shared_ptr<AutoCloseFD> FDPtr;
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typedef list<FDPtr> FDs;
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static void readTempRoots(PathSet & tempRoots, FDs & fds)
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{
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/* Read the `temproots' directory for per-process temporary root
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files. */
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Strings tempRootFiles = readDirectory(
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(format("%1%/%2%") % settings.nixStateDir % tempRootsDir).str());
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foreach (Strings::iterator, i, tempRootFiles) {
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Path path = (format("%1%/%2%/%3%") % settings.nixStateDir % tempRootsDir % *i).str();
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debug(format("reading temporary root file `%1%'") % path);
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FDPtr fd(new AutoCloseFD(open(path.c_str(), O_RDWR, 0666)));
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if (*fd == -1) {
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/* It's okay if the file has disappeared. */
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if (errno == ENOENT) continue;
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throw SysError(format("opening temporary roots file `%1%'") % path);
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}
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/* This should work, but doesn't, for some reason. */
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//FDPtr fd(new AutoCloseFD(openLockFile(path, false)));
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//if (*fd == -1) continue;
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/* Try to acquire a write lock without blocking. This can
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only succeed if the owning process has died. In that case
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we don't care about its temporary roots. */
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if (lockFile(*fd, ltWrite, false)) {
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printMsg(lvlError, format("removing stale temporary roots file `%1%'")
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% path);
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unlink(path.c_str());
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writeFull(*fd, (const unsigned char *) "d", 1);
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continue;
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}
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/* Acquire a read lock. This will prevent the owning process
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from upgrading to a write lock, therefore it will block in
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addTempRoot(). */
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debug(format("waiting for read lock on `%1%'") % path);
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lockFile(*fd, ltRead, true);
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/* Read the entire file. */
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string contents = readFile(*fd);
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/* Extract the roots. */
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string::size_type pos = 0, end;
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while ((end = contents.find((char) 0, pos)) != string::npos) {
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Path root(contents, pos, end - pos);
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debug(format("got temporary root `%1%'") % root);
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assertStorePath(root);
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tempRoots.insert(root);
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pos = end + 1;
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}
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fds.push_back(fd); /* keep open */
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}
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}
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static void findRoots(StoreAPI & store, const Path & path,
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bool recurseSymlinks, bool deleteStale, Roots & roots)
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{
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try {
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struct stat st;
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if (lstat(path.c_str(), &st) == -1)
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throw SysError(format("statting `%1%'") % path);
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printMsg(lvlVomit, format("looking at `%1%'") % path);
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if (S_ISDIR(st.st_mode)) {
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Strings names = readDirectory(path);
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foreach (Strings::iterator, i, names)
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findRoots(store, path + "/" + *i, recurseSymlinks, deleteStale, roots);
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}
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else if (S_ISLNK(st.st_mode)) {
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Path target = absPath(readLink(path), dirOf(path));
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if (isInStore(target)) {
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debug(format("found root `%1%' in `%2%'")
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% target % path);
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Path storePath = toStorePath(target);
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if (store.isValidPath(storePath))
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roots[path] = storePath;
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else
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printMsg(lvlInfo, format("skipping invalid root from `%1%' to `%2%'")
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% path % storePath);
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}
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else if (recurseSymlinks) {
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if (pathExists(target))
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findRoots(store, target, false, deleteStale, roots);
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else if (deleteStale) {
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printMsg(lvlInfo, format("removing stale link from `%1%' to `%2%'") % path % target);
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/* Note that we only delete when recursing, i.e.,
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when we are still in the `gcroots' tree. We
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never delete stuff outside that tree. */
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unlink(path.c_str());
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}
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}
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}
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}
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catch (SysError & e) {
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/* We only ignore permanent failures. */
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if (e.errNo == EACCES || e.errNo == ENOENT || e.errNo == ENOTDIR)
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printMsg(lvlInfo, format("cannot read potential root `%1%'") % path);
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else
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throw;
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}
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}
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static Roots findRoots(StoreAPI & store, bool deleteStale)
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{
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Roots roots;
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Path rootsDir = canonPath((format("%1%/%2%") % settings.nixStateDir % gcRootsDir).str());
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findRoots(store, rootsDir, true, deleteStale, roots);
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return roots;
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}
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Roots LocalStore::findRoots()
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{
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return nix::findRoots(*this, false);
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}
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static void addAdditionalRoots(StoreAPI & store, PathSet & roots)
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{
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Path rootFinder = getEnv("NIX_ROOT_FINDER",
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settings.nixLibexecDir + "/nix/find-runtime-roots.pl");
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if (rootFinder.empty()) return;
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debug(format("executing `%1%' to find additional roots") % rootFinder);
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string result = runProgram(rootFinder);
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Strings paths = tokenizeString<Strings>(result, "\n");
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foreach (Strings::iterator, i, paths) {
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if (isInStore(*i)) {
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Path path = toStorePath(*i);
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if (roots.find(path) == roots.end() && store.isValidPath(path)) {
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debug(format("got additional root `%1%'") % path);
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roots.insert(path);
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}
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}
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}
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}
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struct GCLimitReached { };
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struct LocalStore::GCState
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{
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GCOptions options;
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GCResults & results;
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PathSet roots;
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PathSet tempRoots;
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PathSet dead;
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PathSet alive;
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bool gcKeepOutputs;
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bool gcKeepDerivations;
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unsigned long long bytesInvalidated;
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Path trashDir;
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bool shouldDelete;
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GCState(GCResults & results_) : results(results_), bytesInvalidated(0) { }
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};
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bool LocalStore::isActiveTempFile(const GCState & state,
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const Path & path, const string & suffix)
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{
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return hasSuffix(path, suffix)
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&& state.tempRoots.find(string(path, 0, path.size() - suffix.size())) != state.tempRoots.end();
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}
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void LocalStore::deleteGarbage(GCState & state, const Path & path)
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{
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unsigned long long bytesFreed;
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deletePathWrapped(path, bytesFreed);
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state.results.bytesFreed += bytesFreed;
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}
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void LocalStore::deletePathRecursive(GCState & state, const Path & path)
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{
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checkInterrupt();
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unsigned long long size = 0;
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if (isValidPath(path)) {
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PathSet referrers;
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queryReferrers(path, referrers);
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foreach (PathSet::iterator, i, referrers)
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if (*i != path) deletePathRecursive(state, *i);
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size = queryPathInfo(path).narSize;
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invalidatePathChecked(path);
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}
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struct stat st;
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if (lstat(path.c_str(), &st)) {
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if (errno == ENOENT) return;
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throw SysError(format("getting status of %1%") % path);
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}
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printMsg(lvlInfo, format("deleting `%1%'") % path);
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state.results.paths.insert(path);
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/* If the path is not a regular file or symlink, move it to the
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trash directory. The move is to ensure that later (when we're
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not holding the global GC lock) we can delete the path without
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being afraid that the path has become alive again. Otherwise
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delete it right away. */
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if (S_ISDIR(st.st_mode)) {
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// Estimate the amount freed using the narSize field. FIXME:
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// if the path was not valid, need to determine the actual
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// size.
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state.bytesInvalidated += size;
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// Mac OS X cannot rename directories if they are read-only.
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if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
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throw SysError(format("making `%1%' writable") % path);
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Path tmp = state.trashDir + "/" + baseNameOf(path);
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if (rename(path.c_str(), tmp.c_str()))
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throw SysError(format("unable to rename `%1%' to `%2%'") % path % tmp);
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} else
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deleteGarbage(state, path);
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if (state.results.bytesFreed + state.bytesInvalidated > state.options.maxFreed) {
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printMsg(lvlInfo, format("deleted or invalidated more than %1% bytes; stopping") % state.options.maxFreed);
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throw GCLimitReached();
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}
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}
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bool LocalStore::canReachRoot(GCState & state, PathSet & visited, const Path & path)
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{
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if (visited.find(path) != visited.end()) return false;
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if (state.alive.find(path) != state.alive.end()) {
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return true;
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}
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if (state.dead.find(path) != state.dead.end()) {
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return false;
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}
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if (state.roots.find(path) != state.roots.end()) {
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printMsg(lvlDebug, format("cannot delete `%1%' because it's a root") % path);
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state.alive.insert(path);
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return true;
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}
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visited.insert(path);
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if (!isValidPath(path)) return false;
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PathSet incoming;
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/* Don't delete this path if any of its referrers are alive. */
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queryReferrers(path, incoming);
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/* If gc-keep-derivations is set and this is a derivation, then
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don't delete the derivation if any of the outputs are alive. */
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if (state.gcKeepDerivations && isDerivation(path)) {
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PathSet outputs = queryDerivationOutputs(path);
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foreach (PathSet::iterator, i, outputs)
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if (isValidPath(*i) && queryDeriver(*i) == path)
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incoming.insert(*i);
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}
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/* If gc-keep-outputs is set, then don't delete this path if there
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are derivers of this path that are not garbage. */
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if (state.gcKeepOutputs) {
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PathSet derivers = queryValidDerivers(path);
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foreach (PathSet::iterator, i, derivers)
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incoming.insert(*i);
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}
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foreach (PathSet::iterator, i, incoming)
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if (*i != path)
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if (canReachRoot(state, visited, *i)) {
|
||
state.alive.insert(path);
|
||
return true;
|
||
}
|
||
|
||
return false;
|
||
}
|
||
|
||
|
||
void LocalStore::tryToDelete(GCState & state, const Path & path)
|
||
{
|
||
checkInterrupt();
|
||
|
||
if (path == linksDir || path == state.trashDir) return;
|
||
|
||
startNest(nest, lvlDebug, format("considering whether to delete `%1%'") % path);
|
||
|
||
if (!isValidPath(path)) {
|
||
/* A lock file belonging to a path that we're building right
|
||
now isn't garbage. */
|
||
if (isActiveTempFile(state, path, ".lock")) return;
|
||
|
||
/* Don't delete .chroot directories for derivations that are
|
||
currently being built. */
|
||
if (isActiveTempFile(state, path, ".chroot")) return;
|
||
}
|
||
|
||
PathSet visited;
|
||
|
||
if (canReachRoot(state, visited, path)) {
|
||
printMsg(lvlDebug, format("cannot delete `%1%' because it's still reachable") % path);
|
||
} else {
|
||
/* No path we visited was a root, so everything is garbage.
|
||
But we only delete ‘path’ and its referrers here so that
|
||
‘nix-store --delete’ doesn't have the unexpected effect of
|
||
recursing into derivations and outputs. */
|
||
state.dead.insert(visited.begin(), visited.end());
|
||
if (state.shouldDelete)
|
||
deletePathRecursive(state, 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(const GCState & state)
|
||
{
|
||
AutoCloseDir dir = opendir(linksDir.c_str());
|
||
if (!dir) throw SysError(format("opening directory `%1%'") % linksDir);
|
||
|
||
long long actualSize = 0, unsharedSize = 0;
|
||
|
||
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) {
|
||
unsigned long long size = st.st_blocks * 512ULL;
|
||
actualSize += size;
|
||
unsharedSize += (st.st_nlink - 1) * size;
|
||
continue;
|
||
}
|
||
|
||
printMsg(lvlTalkative, format("deleting unused link `%1%'") % path);
|
||
|
||
if (unlink(path.c_str()) == -1)
|
||
throw SysError(format("deleting `%1%'") % path);
|
||
|
||
state.results.bytesFreed += st.st_blocks * 512;
|
||
}
|
||
|
||
struct stat st;
|
||
if (stat(linksDir.c_str(), &st) == -1)
|
||
throw SysError(format("statting `%1%'") % linksDir);
|
||
long long overhead = st.st_blocks * 512ULL;
|
||
|
||
printMsg(lvlInfo, format("note: currently hard linking saves %.2f MiB")
|
||
% ((unsharedSize - actualSize - overhead) / (1024.0 * 1024.0)));
|
||
}
|
||
|
||
|
||
void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
|
||
{
|
||
GCState state(results);
|
||
state.options = options;
|
||
state.trashDir = settings.nixStore + "/trash";
|
||
state.gcKeepOutputs = settings.gcKeepOutputs;
|
||
state.gcKeepDerivations = settings.gcKeepDerivations;
|
||
|
||
/* Using `--ignore-liveness' with `--delete' can have unintended
|
||
consequences if `gc-keep-outputs' or `gc-keep-derivations' are
|
||
true (the garbage collector will recurse into deleting the
|
||
outputs or derivers, respectively). So disable them. */
|
||
if (options.action == GCOptions::gcDeleteSpecific && options.ignoreLiveness) {
|
||
state.gcKeepOutputs = false;
|
||
state.gcKeepDerivations = false;
|
||
}
|
||
|
||
state.shouldDelete = options.action == GCOptions::gcDeleteDead || options.action == GCOptions::gcDeleteSpecific;
|
||
|
||
/* Acquire the global GC root. This prevents
|
||
a) New roots from being added.
|
||
b) Processes from creating new temporary root files. */
|
||
AutoCloseFD fdGCLock = openGCLock(ltWrite);
|
||
|
||
/* Find the roots. Since we've grabbed the GC lock, the set of
|
||
permanent roots cannot increase now. */
|
||
printMsg(lvlError, format("finding garbage collector roots..."));
|
||
Roots rootMap = options.ignoreLiveness ? Roots() : nix::findRoots(*this, true);
|
||
|
||
foreach (Roots::iterator, i, rootMap) state.roots.insert(i->second);
|
||
|
||
/* Add additional roots returned by the program specified by the
|
||
NIX_ROOT_FINDER environment variable. This is typically used
|
||
to add running programs to the set of roots (to prevent them
|
||
from being garbage collected). */
|
||
if (!options.ignoreLiveness)
|
||
addAdditionalRoots(*this, state.roots);
|
||
|
||
/* Read the temporary roots. This acquires read locks on all
|
||
per-process temporary root files. So after this point no paths
|
||
can be added to the set of temporary roots. */
|
||
FDs fds;
|
||
readTempRoots(state.tempRoots, fds);
|
||
state.roots.insert(state.tempRoots.begin(), state.tempRoots.end());
|
||
|
||
/* After this point the set of roots or temporary roots cannot
|
||
increase, since we hold locks on everything. So everything
|
||
that is not reachable from `roots'. */
|
||
|
||
if (state.shouldDelete) createDirs(state.trashDir);
|
||
|
||
/* Now either delete all garbage paths, or just the specified
|
||
paths (for gcDeleteSpecific). */
|
||
|
||
if (options.action == GCOptions::gcDeleteSpecific) {
|
||
|
||
foreach (PathSet::iterator, i, options.pathsToDelete) {
|
||
assertStorePath(*i);
|
||
tryToDelete(state, *i);
|
||
if (state.dead.find(*i) == state.dead.end())
|
||
throw Error(format("cannot delete path `%1%' since it is still alive") % *i);
|
||
}
|
||
|
||
} else if (options.maxFreed > 0) {
|
||
|
||
if (state.shouldDelete)
|
||
printMsg(lvlError, format("deleting garbage..."));
|
||
else
|
||
printMsg(lvlError, format("determining live/dead paths..."));
|
||
|
||
try {
|
||
|
||
AutoCloseDir dir = opendir(settings.nixStore.c_str());
|
||
if (!dir) throw SysError(format("opening directory `%1%'") % settings.nixStore);
|
||
|
||
/* Read the store and immediately delete all paths that
|
||
aren't valid. When using --max-freed etc., deleting
|
||
invalid paths is preferred over deleting unreachable
|
||
paths, since unreachable paths could become reachable
|
||
again. We don't use readDirectory() here so that GCing
|
||
can start faster. */
|
||
Paths entries;
|
||
struct dirent * dirent;
|
||
while (errno = 0, dirent = readdir(dir)) {
|
||
checkInterrupt();
|
||
string name = dirent->d_name;
|
||
if (name == "." || name == "..") continue;
|
||
Path path = settings.nixStore + "/" + name;
|
||
if (isValidPath(path))
|
||
entries.push_back(path);
|
||
else
|
||
tryToDelete(state, path);
|
||
}
|
||
|
||
dir.close();
|
||
|
||
/* Now delete the unreachable valid paths. Randomise the
|
||
order in which we delete entries to make the collector
|
||
less biased towards deleting paths that come
|
||
alphabetically first (e.g. /nix/store/000...). This
|
||
matters when using --max-freed etc. */
|
||
vector<Path> entries_(entries.begin(), entries.end());
|
||
random_shuffle(entries_.begin(), entries_.end());
|
||
|
||
foreach (vector<Path>::iterator, i, entries_)
|
||
tryToDelete(state, *i);
|
||
|
||
} catch (GCLimitReached & e) {
|
||
}
|
||
}
|
||
|
||
if (state.options.action == GCOptions::gcReturnLive) {
|
||
state.results.paths = state.alive;
|
||
return;
|
||
}
|
||
|
||
if (state.options.action == GCOptions::gcReturnDead) {
|
||
state.results.paths = state.dead;
|
||
return;
|
||
}
|
||
|
||
/* Allow other processes to add to the store from here on. */
|
||
fdGCLock.close();
|
||
|
||
/* Delete the trash directory. */
|
||
printMsg(lvlInfo, format("deleting `%1%'") % state.trashDir);
|
||
deleteGarbage(state, state.trashDir);
|
||
|
||
/* Clean up the links directory. */
|
||
if (options.action == GCOptions::gcDeleteDead || options.action == GCOptions::gcDeleteSpecific) {
|
||
printMsg(lvlError, format("deleting unused links..."));
|
||
removeUnusedLinks(state);
|
||
}
|
||
|
||
/* While we're at it, vacuum the database. */
|
||
if (options.action == GCOptions::gcDeleteDead) vacuumDB();
|
||
}
|
||
|
||
|
||
}
|