diff options
| -rw-r--r-- | src/libstore/gc.cc | 34 |
1 files changed, 18 insertions, 16 deletions
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc index a21ccc9d299c..f6ed7dd2264e 100644 --- a/src/libstore/gc.cc +++ b/src/libstore/gc.cc @@ -56,24 +56,22 @@ int LocalStore::openGCLock(LockType lockType) } -void createSymlink(const Path & link, const Path & target, bool careful) +void createSymlink(const Path & link, const Path & target) { /* Create directories up to `gcRoot'. */ createDirs(dirOf(link)); - /* !!! shouldn't removing and creating the symlink be atomic? */ - - /* Remove the old symlink. */ - if (pathExists(link)) { - if (careful && (!isLink(link) || !isInStore(readLink(link)))) - throw Error(format("cannot create symlink `%1%'; already exists") % link); - unlink(link.c_str()); - } - - /* And create the new one. */ - if (symlink(target.c_str(), link.c_str()) == -1) + /* Create the new symlink. */ + Path tempLink = (format("%1%.tmp-%2%-%3%") + % link % getpid() % rand()).str(); + if (symlink(target.c_str(), tempLink.c_str()) == -1) throw SysError(format("symlinking `%1%' to `%2%'") - % link % target); + % tempLink % target); + + /* Atomically replace the old one. */ + if (rename(tempLink.c_str(), link.c_str()) == -1) + throw SysError(format("cannot rename `%1%' to `%2%'") + % tempLink % link); } @@ -88,7 +86,7 @@ void LocalStore::addIndirectRoot(const Path & path) string hash = printHash32(hashString(htSHA1, path)); Path realRoot = canonPath((format("%1%/%2%/auto/%3%") % nixStateDir % gcRootsDir % hash).str()); - createSymlink(realRoot, path, false); + createSymlink(realRoot, path); } @@ -105,7 +103,11 @@ Path addPermRoot(StoreAPI & store, const Path & _storePath, "(are you running nix-build inside the store?)") % gcRoot); if (indirect) { - createSymlink(gcRoot, storePath, true); + /* Don't clobber the the link if it already exists and doesn't + point to the Nix store. */ + if (pathExists(gcRoot) && (!isLink(gcRoot) || !isInStore(readLink(gcRoot)))) + throw Error(format("cannot create symlink `%1%'; already exists") % gcRoot); + createSymlink(gcRoot, storePath); store.addIndirectRoot(gcRoot); } @@ -120,7 +122,7 @@ Path addPermRoot(StoreAPI & store, const Path & _storePath, % gcRoot % rootsDir); } - createSymlink(gcRoot, storePath, false); + createSymlink(gcRoot, storePath); } /* Check that the root can be found by the garbage collector. |