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LocalStore: Allow the physical and logical store directories to differ

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This is primarily to subsume the functionality of the
copy-from-other-stores substituter. For example, in the NixOS
installer, we can now do (assuming we're in the target chroot, and the
Nix store of the installation CD is bind-mounted on /tmp/nix):

  $ nix-build ... --option substituters 'local?state=/tmp/nix/var&real=/tmp/nix/store'

However, unlike copy-from-other-stores, this also allows write access
to such a store. One application might be fetching substitutes for
/nix/store in a situation where the user doesn't have sufficient
privileges to create /nix, e.g.:

  $ NIX_REMOTE="local?state=/home/alice/nix/var&real=/home/alice/nix/store" nix-build ...
This commit is contained in:
Eelco Dolstra 2016-06-02 15:08:18 +02:00
parent 064816ab98
commit 4494000e04
7 changed files with 68 additions and 158 deletions
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39
src/libstore/gc.cc
View file

@ -370,7 +370,6 @@ struct LocalStore::GCState
bool gcKeepDerivations;
unsigned long long bytesInvalidated;
bool moveToTrash = true;
Path trashDir;
bool shouldDelete;
GCState(GCResults & results_) : results(results_), bytesInvalidated(0) { }
};
@ -407,10 +406,12 @@ void LocalStore::deletePathRecursive(GCState & state, const Path & path)
invalidatePathChecked(path);
}
Path realPath = realStoreDir + "/" + baseNameOf(path);
struct stat st;
if (lstat(path.c_str(), &st)) {
if (lstat(realPath.c_str(), &st)) {
if (errno == ENOENT) return;
throw SysError(format("getting status of %1%") % path);
throw SysError(format("getting status of %1%") % realPath);
}
printMsg(lvlInfo, format("deleting ‘%1%’") % path);
@ -427,20 +428,20 @@ void LocalStore::deletePathRecursive(GCState & state, const Path & path)
// if the path was not valid, need to determine the actual
// size.
try {
if (chmod(path.c_str(), st.st_mode | S_IWUSR) == -1)
throw SysError(format("making ‘%1%’ writable") % path);
Path tmp = state.trashDir + "/" + baseNameOf(path);
if (rename(path.c_str(), tmp.c_str()))
throw SysError(format("unable to rename ‘%1%’ to ‘%2%’") % path % tmp);
if (chmod(realPath.c_str(), st.st_mode | S_IWUSR) == -1)
throw SysError(format("making ‘%1%’ writable") % realPath);
Path tmp = trashDir + "/" + baseNameOf(path);
if (rename(realPath.c_str(), tmp.c_str()))
throw SysError(format("unable to rename ‘%1%’ to ‘%2%’") % realPath % tmp);
state.bytesInvalidated += size;
} catch (SysError & e) {
if (e.errNo == ENOSPC) {
printMsg(lvlInfo, format("note: can't create move ‘%1%’: %2%") % path % e.msg());
deleteGarbage(state, path);
printMsg(lvlInfo, format("note: can't create move ‘%1%’: %2%") % realPath % e.msg());
deleteGarbage(state, realPath);
}
}
} else
deleteGarbage(state, path);
deleteGarbage(state, realPath);
if (state.results.bytesFreed + state.bytesInvalidated > state.options.maxFreed) {
printMsg(lvlInfo, format("deleted or invalidated more than %1% bytes; stopping") % state.options.maxFreed);
@ -508,7 +509,8 @@ void LocalStore::tryToDelete(GCState & state, const Path & path)
{
checkInterrupt();
if (path == linksDir || path == state.trashDir) return;
auto realPath = realStoreDir + "/" + baseNameOf(path);
if (realPath == linksDir || realPath == trashDir) return;
Activity act(*logger, lvlDebug, format("considering whether to delete ‘%1%’") % path);
@ -590,7 +592,6 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
{
GCState state(results);
state.options = options;
state.trashDir = storeDir + "/trash";
state.gcKeepOutputs = settings.gcKeepOutputs;
state.gcKeepDerivations = settings.gcKeepDerivations;
@ -639,9 +640,9 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
that is not reachable from `roots' is garbage. */
if (state.shouldDelete) {
if (pathExists(state.trashDir)) deleteGarbage(state, state.trashDir);
if (pathExists(trashDir)) deleteGarbage(state, trashDir);
try {
createDirs(state.trashDir);
createDirs(trashDir);
} catch (SysError & e) {
if (e.errNo == ENOSPC) {
printMsg(lvlInfo, format("note: can't create trash directory: %1%") % e.msg());
@ -671,8 +672,8 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
try {
AutoCloseDir dir = opendir(storeDir.c_str());
if (!dir) throw SysError(format("opening directory ‘%1%’") % storeDir);
AutoCloseDir dir = opendir(realStoreDir.c_str());
if (!dir) throw SysError(format("opening directory ‘%1%’") % realStoreDir);
/* Read the store and immediately delete all paths that
aren't valid. When using --max-freed etc., deleting
@ -725,8 +726,8 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
fds.clear();
/* Delete the trash directory. */
printMsg(lvlInfo, format("deleting ‘%1%’") % state.trashDir);
deleteGarbage(state, state.trashDir);
printMsg(lvlInfo, format("deleting ‘%1%’") % trashDir);
deleteGarbage(state, trashDir);
/* Clean up the links directory. */
if (options.action == GCOptions::gcDeleteDead || options.action == GCOptions::gcDeleteSpecific) {