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selftests/namespace: second threaded active reference count test

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Test that a namespace remains active while a thread holds an fd to it.
Even after the thread exits, the namespace should remain active as long
as another thread holds a file descriptor to it.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-68-2e6f823ebdc0@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2025-10-29 13:21:21 +01:00
parent 29f083c499
commit ee86103238
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 99 additions and 0 deletions
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99
tools/testing/selftests/namespaces/ns_active_ref_test.c
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@ -2251,4 +2251,103 @@ TEST(thread_ns_inactive_after_exit)
ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
}
/*
* Test that a namespace remains active while a thread holds an fd to it.
* Even after the thread exits, the namespace should remain active as long as
* another thread holds a file descriptor to it.
*/
TEST(thread_ns_fd_keeps_active)
{
pthread_t thread;
struct thread_ns_info info;
struct file_handle *handle;
int pipefd[2];
int syncpipe[2];
int ret;
char sync_byte;
char buf[sizeof(*handle) + MAX_HANDLE_SZ];
ASSERT_EQ(pipe(pipefd), 0);
ASSERT_EQ(pipe(syncpipe), 0);
info.pipefd = pipefd[1];
info.syncfd_read = syncpipe[0];
info.syncfd_write = -1;
info.exit_code = -1;
/* Create thread that will create a namespace */
ret = pthread_create(&thread, NULL, thread_create_namespace, &info);
ASSERT_EQ(ret, 0);
/* Read namespace ID from thread */
__u64 ns_id;
ret = read(pipefd[0], &ns_id, sizeof(ns_id));
if (ret != sizeof(ns_id)) {
sync_byte = 'X';
write(syncpipe[1], &sync_byte, 1);
pthread_join(thread, NULL);
close(pipefd[0]);
close(pipefd[1]);
close(syncpipe[0]);
close(syncpipe[1]);
SKIP(return, "Failed to read namespace ID from thread");
}
TH_LOG("Thread created namespace with ID %llu", (unsigned long long)ns_id);
/* Construct file handle */
handle = (struct file_handle *)buf;
handle->handle_bytes = sizeof(struct nsfs_file_handle);
handle->handle_type = FILEID_NSFS;
struct nsfs_file_handle *fh = (struct nsfs_file_handle *)handle->f_handle;
fh->ns_id = ns_id;
fh->ns_type = 0;
fh->ns_inum = 0;
/* Open namespace while thread is alive */
TH_LOG("Opening namespace while thread is alive");
int nsfd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
ASSERT_GE(nsfd, 0);
/* Signal thread to exit */
TH_LOG("Signaling thread to exit");
sync_byte = 'X';
write(syncpipe[1], &sync_byte, 1);
close(syncpipe[1]);
/* Wait for thread to exit */
pthread_join(thread, NULL);
close(pipefd[0]);
close(pipefd[1]);
close(syncpipe[0]);
if (info.exit_code != 0) {
close(nsfd);
SKIP(return, "Thread failed to create namespace");
}
TH_LOG("Thread exited, but main thread holds fd - namespace should remain active");
/* Namespace should still be active because we hold an fd */
int nsfd2 = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
ASSERT_GE(nsfd2, 0);
/* Verify it's the same namespace */
struct stat st1, st2;
ASSERT_EQ(fstat(nsfd, &st1), 0);
ASSERT_EQ(fstat(nsfd2, &st2), 0);
ASSERT_EQ(st1.st_ino, st2.st_ino);
close(nsfd2);
TH_LOG("Closing fd - namespace should become inactive");
close(nsfd);
/* Now namespace should be inactive */
nsfd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
ASSERT_LT(nsfd, 0);
/* Should fail with ENOENT (inactive) or ESTALE (gone) */
TH_LOG("Namespace inactive as expected: %s (errno=%d)", strerror(errno), errno);
ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
}
TEST_HARNESS_MAIN