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Separate cgroup support from auto-uid-allocation

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The new experimental feature 'cgroups' enables the use of cgroups for
all builds. This allows better containment and enables setting
resource limits and getting some build stats.
This commit is contained in:
Eelco Dolstra 2022-11-18 10:39:28 +01:00
parent f1ab082ac4
commit 128910ba23
6 changed files with 93 additions and 108 deletions
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71
src/libstore/lock.cc
View file

@ -1,7 +1,6 @@
#include "lock.hh"
#include "globals.hh"
#include "pathlocks.hh"
#include "cgroup.hh"
#include <pwd.h>
#include <grp.h>
@ -15,11 +14,6 @@ struct SimpleUserLock : UserLock
gid_t gid;
std::vector<gid_t> supplementaryGIDs;
void kill() override
{
killUser(uid);
}
uid_t getUID() override { assert(uid); return uid; }
uid_t getUIDCount() override { return 1; }
gid_t getGID() override { assert(gid); return gid; }
@ -116,32 +110,6 @@ struct AutoUserLock : UserLock
AutoCloseFD fdUserLock;
uid_t firstUid = 0;
uid_t nrIds = 1;
#if __linux__
std::optional<Path> cgroup;
#endif
~AutoUserLock()
{
#if __linux__
// Get rid of our cgroup, ignoring errors.
if (cgroup) rmdir(cgroup->c_str());
#endif
}
void kill() override
{
#if __linux__
if (cgroup) {
destroyCgroup(*cgroup);
if (mkdir(cgroup->c_str(), 0755) == -1)
throw SysError("creating cgroup '%s'", *cgroup);
} else
#endif
{
assert(firstUid);
killUser(firstUid);
}
}
uid_t getUID() override { assert(firstUid); return firstUid; }
@ -183,55 +151,16 @@ struct AutoUserLock : UserLock
throw SysError("opening user lock '%s'", fnUserLock);
if (lockFile(fd.get(), ltWrite, false)) {
auto s = drainFD(fd.get());
#if __linux__
if (s != "") {
/* Kill the old cgroup, to ensure there are no
processes left over from an interrupted build. */
destroyCgroup(s);
}
#endif
if (ftruncate(fd.get(), 0) == -1)
throw Error("truncating user lock");
auto lock = std::make_unique<AutoUserLock>();
lock->fdUserLock = std::move(fd);
lock->firstUid = settings.startId + i * maxIdsPerBuild;
lock->nrIds = nrIds;
#if __linux__
if (nrIds > 1) {
auto ourCgroups = getCgroups("/proc/self/cgroup");
auto ourCgroup = ourCgroups[""];
if (ourCgroup == "")
throw Error("cannot determine cgroup name from /proc/self/cgroup");
auto ourCgroupPath = canonPath("/sys/fs/cgroup/" + ourCgroup);
if (!pathExists(ourCgroupPath))
throw Error("expected cgroup directory '%s'", ourCgroupPath);
lock->cgroup = fmt("%s/nix-build-%d", ourCgroupPath, lock->firstUid);
/* Record the cgroup in the lock file. This ensures that
if we subsequently get executed under a different parent
cgroup, we kill the previous cgroup first. */
writeFull(lock->fdUserLock.get(), *lock->cgroup);
}
#endif
return lock;
}
}
return nullptr;
}
#if __linux__
std::optional<Path> getCgroup() override { return cgroup; }
#endif
};
std::unique_ptr<UserLock> acquireUserLock(uid_t nrIds)