forked from lix-project/lix
723 lines
24 KiB
C++
723 lines
24 KiB
C++
#include "globals.hh"
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#include "misc.hh"
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#include "pathlocks.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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#ifdef __CYGWIN__
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#include <windows.h>
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#include <sys/cygwin.h>
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#endif
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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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static int openGCLock(LockType lockType)
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{
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Path fnGCLock = (format("%1%/%2%")
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% 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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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, bool careful)
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{
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/* Create directories up to `gcRoot'. */
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createDirs(dirOf(link));
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/* !!! shouldn't removing and creating the symlink be atomic? */
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/* Remove the old symlink. */
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if (pathExists(link)) {
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if (careful && (!isLink(link) || !isInStore(readLink(link))))
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throw Error(format("cannot create symlink `%1%'; already exists") % link);
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unlink(link.c_str());
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}
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/* And create the new one. */
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if (symlink(target.c_str(), link.c_str()) == -1)
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throw SysError(format("symlinking `%1%' to `%2%'")
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% link % target);
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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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% nixStateDir % gcRootsDir % hash).str());
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createSymlink(realRoot, path, false);
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}
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Path addPermRoot(const Path & _storePath, const Path & _gcRoot,
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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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createSymlink(gcRoot, storePath, true);
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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%") % 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, false);
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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 (queryBoolSetting("gc-check-reachability", true)) {
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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%") % 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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deletePath(fnTempRoots);
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fdTempRoots = openLockFile(fnTempRoots, true);
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fdGCLock.close();
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/* Note that on Cygwin a lot of the following complexity
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is unnecessary, since we cannot delete open lock
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files. If we have the lock file open, then it's valid;
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if we can delete it, then it wasn't in use any more.
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Also note that on Cygwin we cannot "upgrade" a lock
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from a read lock to a write lock. */
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#ifndef __CYGWIN__
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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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#else
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break;
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#endif
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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.c_str(), s.size());
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#ifndef __CYGWIN__
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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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#else
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debug(format("releasing write lock on `%1%'") % fnTempRoots);
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lockFile(fdTempRoots, ltNone, true);
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#endif
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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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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%") % nixStateDir % tempRootsDir).str());
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foreach (Strings::iterator, i, tempRootFiles) {
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Path path = (format("%1%/%2%/%3%") % nixStateDir % tempRootsDir % *i).str();
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debug(format("reading temporary root file `%1%'") % path);
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#ifdef __CYGWIN__
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/* On Cygwin we just try to delete the lock file. */
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char win32Path[MAX_PATH];
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cygwin_conv_to_full_win32_path(path.c_str(), win32Path);
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if (DeleteFile(win32Path)) {
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printMsg(lvlError, format("removed stale temporary roots file `%1%'")
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% path);
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continue;
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} else
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debug(format("delete of `%1%' failed: %2%") % path % GetLastError());
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#endif
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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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#ifndef __CYGWIN__
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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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#endif
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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(const Path & path, bool recurseSymlinks,
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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(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(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(bool deleteStale)
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{
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Roots roots;
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Path rootsDir = canonPath((format("%1%/%2%") % nixStateDir % gcRootsDir).str());
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findRoots(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(false);
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}
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static void addAdditionalRoots(PathSet & roots)
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{
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Path rootFinder = getEnv("NIX_ROOT_FINDER",
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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(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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static void dfsVisit(const PathSet & paths, const Path & path,
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PathSet & visited, Paths & sorted)
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{
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if (visited.find(path) != visited.end()) return;
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visited.insert(path);
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PathSet references;
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if (store->isValidPath(path))
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store->queryReferences(path, references);
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foreach (PathSet::iterator, i, references)
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/* Don't traverse into paths that don't exist. That can
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happen due to substitutes for non-existent paths. */
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if (*i != path && paths.find(*i) != paths.end())
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dfsVisit(paths, *i, visited, sorted);
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sorted.push_front(path);
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}
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Paths topoSortPaths(const PathSet & paths)
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{
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Paths sorted;
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PathSet visited;
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foreach (PathSet::const_iterator, i, paths)
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dfsVisit(paths, *i, visited, sorted);
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return sorted;
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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 deleted;
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PathSet live;
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PathSet busy;
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bool gcKeepOutputs;
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bool gcKeepDerivations;
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bool drvsIndexed;
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typedef std::multimap<string, Path> DrvsByName;
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DrvsByName drvsByName; // derivation paths hashed by name attribute
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GCState(GCResults & results_) : results(results_), drvsIndexed(false)
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{
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}
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};
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static bool doDelete(GCOptions::GCAction action)
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{
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return action == GCOptions::gcDeleteDead
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|| action == GCOptions::gcDeleteSpecific;
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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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/* Return all the derivations in the Nix store that have `path' as an
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output. This function assumes that derivations have the same name
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as their outputs. */
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PathSet LocalStore::findDerivers(GCState & state, const Path & path)
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{
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PathSet derivers;
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Path deriver = queryDeriver(path);
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if (deriver != "") derivers.insert(deriver);
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if (!state.drvsIndexed) {
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Paths entries = readDirectory(nixStore);
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foreach (Paths::iterator, i, entries)
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if (isDerivation(*i))
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state.drvsByName.insert(std::pair<string, Path>(
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getNameOfStorePath(*i), nixStore + "/" + *i));
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state.drvsIndexed = true;
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}
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string name = getNameOfStorePath(path);
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// Urgh, I should have used Haskell...
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std::pair<GCState::DrvsByName::iterator, GCState::DrvsByName::iterator> range =
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state.drvsByName.equal_range(name);
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for (GCState::DrvsByName::iterator i = range.first; i != range.second; ++i)
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if (isValidPath(i->second)) {
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Derivation drv = derivationFromPath(i->second);
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foreach (DerivationOutputs::iterator, j, drv.outputs)
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if (j->second.path == path) derivers.insert(i->second);
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}
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return derivers;
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}
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bool LocalStore::tryToDelete(GCState & state, const Path & path)
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{
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if (!pathExists(path)) return true;
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if (state.deleted.find(path) != state.deleted.end()) return true;
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if (state.live.find(path) != state.live.end()) return false;
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startNest(nest, lvlDebug, format("considering whether to delete `%1%'") % path);
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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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goto isLive;
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}
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|
|
if (isValidPath(path)) {
|
|
|
|
/* Recursively try to delete the referrers of this path. If
|
|
any referrer can't be deleted, then this path can't be
|
|
deleted either. */
|
|
PathSet referrers;
|
|
queryReferrers(path, referrers);
|
|
foreach (PathSet::iterator, i, referrers)
|
|
if (*i != path && !tryToDelete(state, *i)) {
|
|
printMsg(lvlDebug, format("cannot delete `%1%' because it has live referrers") % path);
|
|
goto isLive;
|
|
}
|
|
|
|
/* If gc-keep-derivations is set and this is a derivation,
|
|
then don't delete the derivation if any of the outputs are
|
|
live. */
|
|
if (state.gcKeepDerivations && isDerivation(path)) {
|
|
Derivation drv = derivationFromPath(path);
|
|
foreach (DerivationOutputs::iterator, i, drv.outputs)
|
|
if (!tryToDelete(state, i->second.path)) {
|
|
printMsg(lvlDebug, format("cannot delete derivation `%1%' because its output is alive") % path);
|
|
goto isLive;
|
|
}
|
|
}
|
|
|
|
/* If gc-keep-derivations and gc-keep-outputs are both set,
|
|
it's possible that the path has already been deleted (due
|
|
to the recursion below), so bail out. */
|
|
if (!pathExists(path)) return true;
|
|
|
|
/* If gc-keep-outputs is set, then don't delete this path if
|
|
its deriver is not garbage. !!! Nix does not reliably
|
|
store derivers, so we have to look at all derivations to
|
|
determine which of them derive `path'. Since this makes
|
|
the garbage collector very slow to start on large Nix
|
|
stores, here we just look for all derivations that have the
|
|
same name as `path' (where the name is the part of the
|
|
filename after the hash, i.e. the `name' attribute of the
|
|
derivation). This is somewhat hacky: currently, the
|
|
deriver of a path always has the same name as the output,
|
|
but this might change in the future. */
|
|
if (state.gcKeepOutputs) {
|
|
PathSet derivers = findDerivers(state, path);
|
|
foreach (PathSet::iterator, deriver, derivers) {
|
|
/* Break an infinite recursion if gc-keep-derivations
|
|
and gc-keep-outputs are both set by tentatively
|
|
assuming that this path is garbage. This is a safe
|
|
assumption because at this point, the only thing
|
|
that can prevent it from being garbage is the
|
|
deriver. Since tryToDelete() works "upwards"
|
|
through the dependency graph, it won't encouter
|
|
this path except in the call to tryToDelete() in
|
|
the gc-keep-derivation branch. */
|
|
state.deleted.insert(path);
|
|
if (!tryToDelete(state, *deriver)) {
|
|
state.deleted.erase(path);
|
|
printMsg(lvlDebug, format("cannot delete `%1%' because its deriver `%2%' is alive") % path % *deriver);
|
|
goto isLive;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
else {
|
|
|
|
/* A lock file belonging to a path that we're building right
|
|
now isn't garbage. */
|
|
if (isActiveTempFile(state, path, ".lock")) return false;
|
|
|
|
/* Don't delete .chroot directories for derivations that are
|
|
currently being built. */
|
|
if (isActiveTempFile(state, path, ".chroot")) return false;
|
|
|
|
}
|
|
|
|
/* The path is garbage, so delete it. */
|
|
if (doDelete(state.options.action)) {
|
|
printMsg(lvlInfo, format("deleting `%1%'") % path);
|
|
|
|
unsigned long long bytesFreed, blocksFreed;
|
|
deleteFromStore(path, bytesFreed, blocksFreed);
|
|
state.results.bytesFreed += bytesFreed;
|
|
state.results.blocksFreed += blocksFreed;
|
|
|
|
if (state.options.maxFreed && state.results.bytesFreed > state.options.maxFreed) {
|
|
printMsg(lvlInfo, format("deleted more than %1% bytes; stopping") % state.options.maxFreed);
|
|
throw GCLimitReached();
|
|
}
|
|
|
|
if (state.options.maxLinks) {
|
|
struct stat st;
|
|
if (stat(nixStore.c_str(), &st) == -1)
|
|
throw SysError(format("statting `%1%'") % nixStore);
|
|
if (st.st_nlink < state.options.maxLinks) {
|
|
printMsg(lvlInfo, format("link count on the store has dropped below %1%; stopping") % state.options.maxLinks);
|
|
throw GCLimitReached();
|
|
}
|
|
}
|
|
|
|
} else
|
|
printMsg(lvlTalkative, format("would delete `%1%'") % path);
|
|
|
|
state.deleted.insert(path);
|
|
if (state.options.action != GCOptions::gcReturnLive)
|
|
state.results.paths.insert(path);
|
|
return true;
|
|
|
|
isLive:
|
|
state.live.insert(path);
|
|
if (state.options.action == GCOptions::gcReturnLive)
|
|
state.results.paths.insert(path);
|
|
return false;
|
|
}
|
|
|
|
|
|
void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
|
|
{
|
|
GCState state(results);
|
|
state.options = options;
|
|
|
|
state.gcKeepOutputs = queryBoolSetting("gc-keep-outputs", false);
|
|
state.gcKeepDerivations = queryBoolSetting("gc-keep-derivations", true);
|
|
|
|
/* 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(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(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'. */
|
|
|
|
/* 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);
|
|
if (!tryToDelete(state, *i))
|
|
throw Error(format("cannot delete path `%1%' since it is still alive") % *i);
|
|
}
|
|
|
|
} else {
|
|
|
|
printMsg(lvlError, format("reading the Nix store..."));
|
|
Paths entries = readDirectory(nixStore);
|
|
|
|
/* 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());
|
|
|
|
if (doDelete(state.options.action))
|
|
printMsg(lvlError, format("deleting garbage..."));
|
|
else
|
|
printMsg(lvlError, format("determining live/dead paths..."));
|
|
|
|
try {
|
|
foreach (vector<Path>::iterator, i, entries_)
|
|
tryToDelete(state, canonPath(nixStore + "/" + *i));
|
|
} catch (GCLimitReached & e) {
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
}
|