[PATCH v6 5/5] nfsd: add the infrastructure to handle the cld upcall

[Jeff Layton <jlayton@redhat.com>]

...and add a mechanism for switching between the "legacy" tracker and
the new one. The decision is made by looking to see whether the
v4recoverydir exists. If it does, then the legacy client tracker is
used.

If it's not, then the kernel will create a "cld" pipe in rpc_pipefs.
That pipe is used to talk to a daemon for handling the upcall.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
 fs/nfsd/nfs4recover.c |  365 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 364 insertions(+), 1 deletions(-)

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index ccd9b97..bb91ad6 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -1,5 +1,6 @@
 /*
 *  Copyright (c) 2004 The Regents of the University of Michigan.
+*  Copyright (c) 2012 Jeff Layton <jlayton@redhat.com>
 *  All rights reserved.
 *
 *  Andy Adamson <andros@citi.umich.edu>
@@ -36,6 +37,10 @@
 #include <linux/namei.h>
 #include <linux/crypto.h>
 #include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/sunrpc/rpc_pipe_fs.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/nfsd/cld.h>
 
 #include "nfsd.h"
 #include "state.h"
@@ -478,12 +483,370 @@ static struct nfsd4_client_tracking_ops nfsd4_legacy_tracking_ops = {
 	.grace_done	= nfsd4_recdir_purge_old,
 };
 
+/* Globals */
+#define NFSD_PIPE_DIR		"/nfsd"
+
+static struct dentry *cld_pipe;
+
+/* list of cld_msg's that are currently in use */
+static DEFINE_SPINLOCK(cld_lock);
+static LIST_HEAD(cld_list);
+static unsigned int cld_xid;
+
+struct cld_upcall {
+	struct list_head	cu_list;
+	struct task_struct	*cu_task;
+	struct cld_msg	cu_msg;
+};
+
+static int
+__cld_pipe_upcall(struct cld_msg *cmsg)
+{
+	int ret;
+	struct rpc_pipe_msg msg;
+	struct inode *inode = cld_pipe->d_inode;
+
+	memset(&msg, 0, sizeof(msg));
+	msg.data = cmsg;
+	msg.len = sizeof(*cmsg);
+
+	/*
+	 * Set task state before we queue the upcall. That prevents
+	 * wake_up_process in the downcall from racing with schedule.
+	 */
+	set_current_state(TASK_UNINTERRUPTIBLE);
+	ret = rpc_queue_upcall(inode, &msg);
+	if (ret < 0) {
+		set_current_state(TASK_RUNNING);
+		goto out;
+	}
+
+	schedule();
+	set_current_state(TASK_RUNNING);
+
+	if (msg.errno < 0)
+		ret = msg.errno;
+out:
+	return ret;
+}
+
+static int
+cld_pipe_upcall(struct cld_msg *cmsg)
+{
+	int ret;
+
+	/*
+	 * -EAGAIN occurs when pipe is closed and reopened while there are
+	 *  upcalls queued.
+	 */
+	do {
+		ret = __cld_pipe_upcall(cmsg);
+	} while (ret == -EAGAIN);
+
+	return ret;
+}
+
+static ssize_t
+cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
+{
+	struct cld_upcall *tmp, *cup;
+	struct cld_msg *cmsg = (struct cld_msg *)src;
+	uint32_t xid;
+
+	if (mlen != sizeof(*cmsg)) {
+		dprintk("%s: got %lu bytes, expected %lu\n", __func__, mlen,
+			sizeof(*cmsg));
+		return -EINVAL;
+	}
+
+	/* copy just the xid so we can try to find that */
+	if (copy_from_user(&xid, &cmsg->cm_xid, sizeof(xid)) != 0) {
+		dprintk("%s: error when copying xid from userspace", __func__);
+		return -EFAULT;
+	}
+
+	/* walk the list and find corresponding xid */
+	cup = NULL;
+	spin_lock(&cld_lock);
+	list_for_each_entry(tmp, &cld_list, cu_list) {
+		if (get_unaligned(&tmp->cu_msg.cm_xid) == xid) {
+			cup = tmp;
+			list_del_init(&cup->cu_list);
+			break;
+		}
+	}
+	spin_unlock(&cld_lock);
+
+	/* couldn't find upcall? */
+	if (!cup) {
+		dprintk("%s: couldn't find upcall -- xid=%u\n", __func__,
+			cup->cu_msg.cm_xid);
+		return -EINVAL;
+	}
+
+	if (copy_from_user(&cup->cu_msg, src, mlen) != 0)
+		return -EFAULT;
+
+	wake_up_process(cup->cu_task);
+	return mlen;
+}
+
+static void
+cld_pipe_destroy_msg(struct rpc_pipe_msg *msg)
+{
+	struct cld_msg *cmsg = msg->data;
+	struct cld_upcall *cup = container_of(cmsg, struct cld_upcall,
+						 cu_msg);
+
+	/* errno >= 0 means we got a downcall */
+	if (msg->errno >= 0)
+		return;
+
+	wake_up_process(cup->cu_task);
+}
+
+static const struct rpc_pipe_ops cld_upcall_ops = {
+	.upcall		= rpc_pipe_generic_upcall,
+	.downcall	= cld_pipe_downcall,
+	.destroy_msg	= cld_pipe_destroy_msg,
+};
+
+/* Initialize rpc_pipefs pipe for communication with client tracking daemon */
+static int
+nfsd4_init_cld_pipe(void)
+{
+	int ret;
+	struct path path;
+	struct vfsmount *mnt;
+
+	if (cld_pipe)
+		return 0;
+
+	mnt = rpc_get_mount();
+	if (IS_ERR(mnt))
+		return PTR_ERR(mnt);
+
+	ret = vfs_path_lookup(mnt->mnt_root, mnt, NFSD_PIPE_DIR, 0, &path);
+	if (ret)
+		goto err;
+
+	cld_pipe = rpc_mkpipe(path.dentry, "cld", NULL,
+				&cld_upcall_ops, RPC_PIPE_WAIT_FOR_OPEN);
+	path_put(&path);
+	if (!IS_ERR(cld_pipe))
+		return 0;
+
+	ret = PTR_ERR(cld_pipe);
+err:
+	rpc_put_mount();
+	printk(KERN_ERR "NFSD: unable to create nfsdcld upcall pipe (%d)\n",
+			ret);
+	return ret;
+}
+
+static void
+nfsd4_remove_cld_pipe(void)
+{
+	int ret;
+
+	ret = rpc_unlink(cld_pipe);
+	if (ret)
+		printk(KERN_ERR "NFSD: error removing cld pipe: %d\n", ret);
+	cld_pipe = NULL;
+	rpc_put_mount();
+}
+
+static struct cld_upcall *
+alloc_cld_upcall(void)
+{
+	struct cld_upcall *new, *tmp;
+
+	new = kzalloc(sizeof(*new), GFP_KERNEL);
+	if (!new)
+		return new;
+
+	/* FIXME: hard cap on number in flight? */
+restart_search:
+	spin_lock(&cld_lock);
+	list_for_each_entry(tmp, &cld_list, cu_list) {
+		if (tmp->cu_msg.cm_xid == cld_xid) {
+			cld_xid++;
+			spin_unlock(&cld_lock);
+			goto restart_search;
+		}
+	}
+	new->cu_task = current;
+	new->cu_msg.cm_vers = CLD_UPCALL_VERSION;
+	put_unaligned(cld_xid++, &new->cu_msg.cm_xid);
+	list_add(&new->cu_list, &cld_list);
+	spin_unlock(&cld_lock);
+
+	dprintk("%s: allocated xid %u\n", __func__, new->cu_msg.cm_xid);
+
+	return new;
+}
+
+static void
+free_cld_upcall(struct cld_upcall *victim)
+{
+	spin_lock(&cld_lock);
+	list_del(&victim->cu_list);
+	spin_unlock(&cld_lock);
+	kfree(victim);
+}
+
+/* Ask daemon to create a new record */
+static void
+nfsd4_cld_create(struct nfs4_client *clp)
+{
+	int ret;
+	struct cld_upcall *cup;
+
+	/* Don't upcall if it's already stored */
+	if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
+		return;
+
+	cup = alloc_cld_upcall();
+	if (!cup) {
+		ret = -ENOMEM;
+		goto out_err;
+	}
+
+	cup->cu_msg.cm_cmd = Cld_Create;
+	cup->cu_msg.cm_u.cm_name.cn_len = clp->cl_name.len;
+	memcpy(cup->cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
+			clp->cl_name.len);
+
+	ret = cld_pipe_upcall(&cup->cu_msg);
+	if (!ret) {
+		ret = cup->cu_msg.cm_status;
+		set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
+	}
+
+	free_cld_upcall(cup);
+out_err:
+	if (ret)
+		printk(KERN_ERR "NFSD: Unable to create client "
+				"record on stable storage: %d\n", ret);
+}
+
+/* Ask daemon to create a new record */
+static void
+nfsd4_cld_remove(struct nfs4_client *clp)
+{
+	int ret;
+	struct cld_upcall *cup;
+
+	/* Don't upcall if it's already removed */
+	if (!test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
+		return;
+
+	cup = alloc_cld_upcall();
+	if (!cup) {
+		ret = -ENOMEM;
+		goto out_err;
+	}
+
+	cup->cu_msg.cm_cmd = Cld_Remove;
+	cup->cu_msg.cm_u.cm_name.cn_len = clp->cl_name.len;
+	memcpy(cup->cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
+			clp->cl_name.len);
+
+	ret = cld_pipe_upcall(&cup->cu_msg);
+	if (!ret) {
+		ret = cup->cu_msg.cm_status;
+		clear_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
+	}
+
+	free_cld_upcall(cup);
+out_err:
+	if (ret)
+		printk(KERN_ERR "NFSD: Unable to remove client "
+				"record from stable storage: %d\n", ret);
+}
+
+/* Check for presence of a record, and update its timestamp */
+static int
+nfsd4_cld_check(struct nfs4_client *clp)
+{
+	int ret;
+	struct cld_upcall *cup;
+
+	/* Don't upcall if one was already stored during this grace pd */
+	if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
+		return 0;
+
+	cup = alloc_cld_upcall();
+	if (!cup) {
+		printk(KERN_ERR "NFSD: Unable to check client record on "
+				"stable storage: %d\n", -ENOMEM);
+		return -ENOMEM;
+	}
+
+	cup->cu_msg.cm_cmd = Cld_Check;
+	cup->cu_msg.cm_u.cm_name.cn_len = clp->cl_name.len;
+	memcpy(cup->cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
+			clp->cl_name.len);
+
+	ret = cld_pipe_upcall(&cup->cu_msg);
+	if (!ret) {
+		ret = cup->cu_msg.cm_status;
+		set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
+	}
+
+	free_cld_upcall(cup);
+	return ret;
+}
+
+static void
+nfsd4_cld_grace_done(time_t boot_time)
+{
+	int ret;
+	struct cld_upcall *cup;
+
+	cup = alloc_cld_upcall();
+	if (!cup) {
+		ret = -ENOMEM;
+		goto out_err;
+	}
+
+	cup->cu_msg.cm_cmd = Cld_GraceDone;
+	cup->cu_msg.cm_u.cm_gracetime = (int64_t)boot_time;
+	ret = cld_pipe_upcall(&cup->cu_msg);
+	if (!ret)
+		ret = cup->cu_msg.cm_status;
+
+	free_cld_upcall(cup);
+out_err:
+	if (ret)
+		printk(KERN_ERR "NFSD: Unable to end grace period: %d\n", ret);
+}
+
+static struct nfsd4_client_tracking_ops nfsd4_cld_tracking_ops = {
+	.init		= nfsd4_init_cld_pipe,
+	.exit		= nfsd4_remove_cld_pipe,
+	.create		= nfsd4_cld_create,
+	.remove		= nfsd4_cld_remove,
+	.check		= nfsd4_cld_check,
+	.grace_done	= nfsd4_cld_grace_done,
+};
+
 int
 nfsd4_client_tracking_init(void)
 {
 	int status;
+	struct path path;
 
-	client_tracking_ops = &nfsd4_legacy_tracking_ops;
+	if (!client_tracking_ops) {
+		client_tracking_ops = &nfsd4_cld_tracking_ops;
+		status = kern_path(nfs4_recoverydir(), LOOKUP_FOLLOW, &path);
+		if (!status) {
+			if (S_ISDIR(path.dentry->d_inode->i_mode))
+				client_tracking_ops =
+						&nfsd4_legacy_tracking_ops;
+			path_put(&path);
+		}
+	}
 
 	status = client_tracking_ops->init();
 	if (status) {
-- 
1.7.7.6