On Feb 14, 2025 / 13:13, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@xxxxxxxxxx> > > As mentioned in the previous patch, trying to isolate processes from > separate test instances through the use of distinct Unix process > sessions is annoying due to the many complications with signal handling. > > Instead, we could just use nsexec to run the test program with a private > pid namespace so that each test instance can only see its own processes; > and private mount namespace so that tests writing to /tmp cannot clobber > other tests or the stuff running on the main system. Further, the > process created by the clone(CLONE_NEWPID) call is considered the init > process of that pid namespace, so all processes will be SIGKILL'd when > the init process terminates, so we no longer need systemd scopes for > externally enforced cleanup. > > However, it's not guaranteed that a particular kernel has pid and mount > namespaces enabled. Mount (2.4.19) and pid (2.6.24) namespaces have > been around for a long time, but there's no hard requirement for the > latter to be enabled in the kernel. Therefore, this bugfix slips > namespace support in alongside the session id thing. > > Declaring CONFIG_PID_NS=n a deprecated configuration and removing > support should be a separate conversation, not something that I have to > do in a bug fix to get mainline QA back up. > > Note that the new helper cannot unmount the /proc it inherits before > mounting a pidns-specific /proc because generic/504 relies on being able > to read the init_pid_ns (aka systemwide) version of /proc/locks to find > a file lock that was taken and leaked by a process. Hello Darrick, I ran fstests for zoned btrfs using the latest fstests tag v2025.02.23, and observed all test cases failed with my set up. I bisected and found that this commit is the trigger. Let me share my observations. For example, btrfs/001.out.bad contents are as follows: QA output created by 001 mount: bad usage Try 'mount --help' for more information. common/rc: retrying test device mount with external set mount: bad usage Try 'mount --help' for more information. common/rc: could not mount /dev/sda on common/config: TEST_DIR (/tmp/test) is not a directory As the last line above shows, fstests failed to find out TEST_DIR, /tmp/test. My set up uses mount point directories in tmpfs, /tmp/*: export TEST_DIR=/tmp/test export SCRATCH_MNT=/tmp/scratch I guessed that tmpfs might be a cause. As a trial, I modified these to, export TEST_DIR=/var/test export SCRATCH_MNT=/var/scratch then I observed the failures disappeared. I guess this implies that the commit for the private pid/mount namespace makes tmpfs unique to each namespace. Then, the the mount points in tmpfs were not found in the private namespaces context, probably. If this guess is correct, in indicates that tmpfs can no longer be used for fstests mount points. Is this expected?
