fs/ecryptfs/kthread.c

Source file repositories/reference/linux-study-clean/fs/ecryptfs/kthread.c

File Facts

System
Linux kernel
Corpus path
fs/ecryptfs/kthread.c
Extension
.c
Size
4382 bytes
Lines
160
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct ecryptfs_open_req {
	struct file **lower_file;
	struct path path;
	struct completion done;
	struct list_head kthread_ctl_list;
};

static struct ecryptfs_kthread_ctl {
#define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001
	u32 flags;
	struct mutex mux;
	struct list_head req_list;
	wait_queue_head_t wait;
} ecryptfs_kthread_ctl;

static struct task_struct *ecryptfs_kthread;

/**
 * ecryptfs_threadfn
 * @ignored: ignored
 *
 * The eCryptfs kernel thread that has the responsibility of getting
 * the lower file with RW permissions.
 *
 * Returns zero on success; non-zero otherwise
 */
static int ecryptfs_threadfn(void *ignored)
{
	set_freezable();
	while (1)  {
		struct ecryptfs_open_req *req;

		wait_event_freezable(
			ecryptfs_kthread_ctl.wait,
			(!list_empty(&ecryptfs_kthread_ctl.req_list)
			 || kthread_should_stop()));
		mutex_lock(&ecryptfs_kthread_ctl.mux);
		if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
			mutex_unlock(&ecryptfs_kthread_ctl.mux);
			goto out;
		}
		while (!list_empty(&ecryptfs_kthread_ctl.req_list)) {
			req = list_first_entry(&ecryptfs_kthread_ctl.req_list,
					       struct ecryptfs_open_req,
					       kthread_ctl_list);
			list_del(&req->kthread_ctl_list);
			*req->lower_file = dentry_open(&req->path,
				(O_RDWR | O_LARGEFILE), current_cred());
			complete(&req->done);
		}
		mutex_unlock(&ecryptfs_kthread_ctl.mux);
	}
out:
	return 0;
}

int __init ecryptfs_init_kthread(void)
{
	int rc = 0;

	mutex_init(&ecryptfs_kthread_ctl.mux);
	init_waitqueue_head(&ecryptfs_kthread_ctl.wait);
	INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list);
	ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL,
				       "ecryptfs-kthread");
	if (IS_ERR(ecryptfs_kthread)) {
		rc = PTR_ERR(ecryptfs_kthread);
		printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]"
		       "\n", __func__, rc);
	}
	return rc;
}

void ecryptfs_destroy_kthread(void)
{
	struct ecryptfs_open_req *req, *tmp;

	mutex_lock(&ecryptfs_kthread_ctl.mux);
	ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE;
	list_for_each_entry_safe(req, tmp, &ecryptfs_kthread_ctl.req_list,
				 kthread_ctl_list) {
		list_del(&req->kthread_ctl_list);
		*req->lower_file = ERR_PTR(-EIO);
		complete(&req->done);
	}
	mutex_unlock(&ecryptfs_kthread_ctl.mux);
	kthread_stop(ecryptfs_kthread);
	wake_up(&ecryptfs_kthread_ctl.wait);
}

Annotation

Implementation Notes