Re: [PATCH v2 2/3] nfsd: un-deprecate nfsdcld

[Scott Mayhew <smayhew@redhat.com>]

On Wed, 19 Dec 2018, Jeff Layton wrote:

> On Tue, 2018-12-18 at 09:29 -0500, Scott Mayhew wrote:
> > When nfsdcld was released, it was quickly deprecated in favor of the
> > nfsdcltrack usermodehelper, so as to not require another running daemon.
> > That prevents NFSv4 clients from reclaiming locks from nfsd's running in
> > containers, since neither nfsdcltrack nor the legacy client tracking
> > code work in containers.
> > 
> > This commit un-deprecates the use of nfsdcld, with one twist: we will
> > populate the reclaim_str_hashtbl on startup.
> > 
> > During client tracking initialization, do an upcall ("GraceStart") to
> > nfsdcld to get a list of clients from the database.  nfsdcld will do
> > one downcall with a status of -EINPROGRESS for each client record in
> > the database, which in turn will cause an nfs4_client_reclaim to be
> > added to the reclaim_str_hashtbl.  When complete, nfsdcld will do a
> > final downcall with a status of 0.
> > 
> > This will save nfsd from having to do an upcall to the daemon during
> > nfs4_check_open_reclaim() processing.
> > 
> > Even though nfsdcld was quickly deprecated, there is a very small chance
> > of old nfsdcld daemons running in the wild.  These will respond to the
> > new "GraceStart" upcall with -EOPNOTSUPP, in which case we will log a
> > message and fall back to the original nfsdcld tracking ops (now called
> > nfsd4_cld_tracking_ops_v0).
> > 
> > Signed-off-by: Scott Mayhew <smayhew@redhat.com>
> > ---
> >  fs/nfsd/nfs4recover.c         | 225 ++++++++++++++++++++++++++++++++--
> >  include/uapi/linux/nfsd/cld.h |   1 +
> >  2 files changed, 218 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> > index 2243b909b407..89c2a27956d0 100644
> > --- a/fs/nfsd/nfs4recover.c
> > +++ b/fs/nfsd/nfs4recover.c
> > @@ -779,6 +779,34 @@ cld_pipe_upcall(struct rpc_pipe *pipe, struct cld_msg *cmsg)
> >  	return ret;
> >  }
> >  
> > +static ssize_t
> > +__cld_pipe_inprogress_downcall(const struct cld_msg __user *cmsg,
> > +		struct nfsd_net *nn)
> > +{
> > +	uint8_t cmd;
> > +	struct xdr_netobj name;
> > +	uint16_t namelen;
> > +
> > +	if (get_user(cmd, &cmsg->cm_cmd)) {
> > +		dprintk("%s: error when copying cmd from userspace", __func__);
> > +		return -EFAULT;
> > +	}
> > +	if (cmd == Cld_GraceStart) {
> > +		if (get_user(namelen, &cmsg->cm_u.cm_name.cn_len))
> > +			return -EFAULT;
> > +		name.data = memdup_user(&cmsg->cm_u.cm_name.cn_id, namelen);
> > +		if (IS_ERR_OR_NULL(name.data))
> > +			return -EFAULT;
> > +		name.len = namelen;
> > +		if (!nfs4_client_to_reclaim(name, nn)) {
> > +			kfree(name.data);
> > +			return -EFAULT;
> > +		}
> > +		return sizeof(*cmsg);
> > +	}
> > +	return -EFAULT;
> > +}
> > +
> >  static ssize_t
> >  cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
> >  {
> > @@ -788,6 +816,7 @@ cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
> >  	struct nfsd_net *nn = net_generic(file_inode(filp)->i_sb->s_fs_info,
> >  						nfsd_net_id);
> >  	struct cld_net *cn = nn->cld_net;
> > +	int16_t status;
> >  
> >  	if (mlen != sizeof(*cmsg)) {
> >  		dprintk("%s: got %zu bytes, expected %zu\n", __func__, mlen,
> > @@ -801,13 +830,24 @@ cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
> >  		return -EFAULT;
> >  	}
> >  
> > +	/*
> > +	 * copy the status so we know whether to remove the upcall from the
> > +	 * list (for -EINPROGRESS, we just want to make sure the xid is
> > +	 * valid, not remove the upcall from the list)
> > +	 */
> > +	if (get_user(status, &cmsg->cm_status)) {
> > +		dprintk("%s: error when copying status from userspace", __func__);
> > +		return -EFAULT;
> > +	}
> > +
> >  	/* walk the list and find corresponding xid */
> >  	cup = NULL;
> >  	spin_lock(&cn->cn_lock);
> >  	list_for_each_entry(tmp, &cn->cn_list, cu_list) {
> >  		if (get_unaligned(&tmp->cu_msg.cm_xid) == xid) {
> >  			cup = tmp;
> > -			list_del_init(&cup->cu_list);
> > +			if (status != -EINPROGRESS)
> > +				list_del_init(&cup->cu_list);
> >  			break;
> >  		}
> >  	}
> > @@ -819,6 +859,9 @@ cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
> >  		return -EINVAL;
> >  	}
> >  
> > +	if (status == -EINPROGRESS)
> > +		return __cld_pipe_inprogress_downcall(cmsg, nn);
> > +
> >  	if (copy_from_user(&cup->cu_msg, src, mlen) != 0)
> >  		return -EFAULT;
> >  
> > @@ -1065,9 +1108,14 @@ nfsd4_cld_remove(struct nfs4_client *clp)
> >  				"record from stable storage: %d\n", ret);
> >  }
> >  
> > -/* Check for presence of a record, and update its timestamp */
> > +/*
> > + * For older nfsdcld's that do not allow us to "slurp" the clients
> > + * from the tracking database during startup.
> > + *
> > + * Check for presence of a record, and update its timestamp
> > + */
> >  static int
> > -nfsd4_cld_check(struct nfs4_client *clp)
> > +nfsd4_cld_check_v0(struct nfs4_client *clp)
> >  {
> >  	int ret;
> >  	struct cld_upcall *cup;
> > @@ -1100,8 +1148,61 @@ nfsd4_cld_check(struct nfs4_client *clp)
> >  	return ret;
> >  }
> >  
> > +/*
> > + * For newer nfsdcld's that allow us to "slurp" the clients
> > + * from the tracking database during startup.
> > + *
> > + * Check for presence of a record in the reclaim_str_hashtbl
> > + */
> > +static int
> > +nfsd4_cld_check(struct nfs4_client *clp)
> > +{
> > +	struct nfs4_client_reclaim *crp;
> > +	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
> > +
> > +	/* did we already find that this client is stable? */
> > +	if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
> > +		return 0;
> > +
> > +	/* look for it in the reclaim hashtable otherwise */
> > +	crp = nfsd4_find_reclaim_client(clp->cl_name, nn);
> > +	if (crp) {
> > +		crp->cr_clp = clp;
> > +		return 0;
> > +	}
> > +
> > +	return -ENOENT;
> > +}
> > +
> > +static int
> > +nfsd4_cld_grace_start(struct nfsd_net *nn)
> > +{
> > +	int ret;
> > +	struct cld_upcall *cup;
> > +	struct cld_net *cn = nn->cld_net;
> > +
> > +	cup = alloc_cld_upcall(cn);
> > +	if (!cup) {
> > +		ret = -ENOMEM;
> > +		goto out_err;
> > +	}
> > +
> > +	cup->cu_msg.cm_cmd = Cld_GraceStart;
> > +	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_msg);
> > +	if (!ret)
> > +		ret = cup->cu_msg.cm_status;
> > +
> > +	free_cld_upcall(cup);
> > +out_err:
> > +	if (ret)
> > +		dprintk("%s: Unable to get clients from userspace: %d\n",
> > +			__func__, ret);
> > +	return ret;
> > +}
> > +
> > +/* For older nfsdcld's that need cm_gracetime */
> >  static void
> > -nfsd4_cld_grace_done(struct nfsd_net *nn)
> > +nfsd4_cld_grace_done_v0(struct nfsd_net *nn)
> >  {
> >  	int ret;
> >  	struct cld_upcall *cup;
> > @@ -1125,11 +1226,118 @@ nfsd4_cld_grace_done(struct nfsd_net *nn)
> >  		printk(KERN_ERR "NFSD: Unable to end grace period: %d\n", ret);
> >  }
> >  
> > -static const struct nfsd4_client_tracking_ops nfsd4_cld_tracking_ops = {
> > +/*
> > + * For newer nfsdcld's that do not need cm_gracetime.  We also need to call
> > + * nfs4_release_reclaim() to clear out the reclaim_str_hashtbl.
> > + */
> > +static void
> > +nfsd4_cld_grace_done(struct nfsd_net *nn)
> > +{
> > +	int ret;
> > +	struct cld_upcall *cup;
> > +	struct cld_net *cn = nn->cld_net;
> > +
> > +	cup = alloc_cld_upcall(cn);
> > +	if (!cup) {
> > +		ret = -ENOMEM;
> > +		goto out_err;
> > +	}
> > +
> > +	cup->cu_msg.cm_cmd = Cld_GraceDone;
> > +	ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_msg);
> > +	if (!ret)
> > +		ret = cup->cu_msg.cm_status;
> > +
> > +	free_cld_upcall(cup);
> > +out_err:
> > +	nfs4_release_reclaim(nn);
> > +	if (ret)
> > +		printk(KERN_ERR "NFSD: Unable to end grace period: %d\n", ret);
> > +}
> > +
> > +static int
> > +nfs4_cld_state_init(struct net *net)
> > +{
> > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > +	int i;
> > +
> > +	nn->reclaim_str_hashtbl = kmalloc_array(CLIENT_HASH_SIZE,
> > +						sizeof(struct list_head),
> > +						GFP_KERNEL);
> > +	if (!nn->reclaim_str_hashtbl)
> > +		return -ENOMEM;
> > +
> > +	for (i = 0; i < CLIENT_HASH_SIZE; i++)
> > +		INIT_LIST_HEAD(&nn->reclaim_str_hashtbl[i]);
> > +	nn->reclaim_str_hashtbl_size = 0;
> > +
> > +	return 0;
> > +}
> > +
> > +static void
> > +nfs4_cld_state_shutdown(struct net *net)
> > +{
> > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > +
> > +	kfree(nn->reclaim_str_hashtbl);
> > +}
> > +
> > +static int
> > +nfsd4_cld_tracking_init(struct net *net)
> > +{
> > +	int status;
> > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > +
> > +	status = nfs4_cld_state_init(net);
> > +	if (status)
> > +		return status;
> > +
> > +	status = nfsd4_init_cld_pipe(net);
> > +	if (status)
> > +		goto err_shutdown;
> > +
> > +	status = nfsd4_cld_grace_start(nn);
> > +	if (status) {
> > +		if (status == -EOPNOTSUPP)
> > +			printk(KERN_WARNING "NFSD: Please upgrade nfsdcld.\n");
> > +		nfs4_release_reclaim(nn);
> > +		goto err_remove;
> > +	}
> > +	return 0;
> > +
> > +err_remove:
> > +	nfsd4_remove_cld_pipe(net);
> > +err_shutdown:
> > +	nfs4_cld_state_shutdown(net);
> > +	return status;
> > +}
> > +
> > +static void
> > +nfsd4_cld_tracking_exit(struct net *net)
> > +{
> > +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> > +
> > +	nfs4_release_reclaim(nn);
> > +	nfsd4_remove_cld_pipe(net);
> > +	nfs4_cld_state_shutdown(net);
> > +}
> > +
> > +/* For older nfsdcld's */
> > +static const struct nfsd4_client_tracking_ops nfsd4_cld_tracking_ops_v0 = {
> >  	.init		= nfsd4_init_cld_pipe,
> >  	.exit		= nfsd4_remove_cld_pipe,
> >  	.create		= nfsd4_cld_create,
> >  	.remove		= nfsd4_cld_remove,
> > +	.check		= nfsd4_cld_check_v0,
> > +	.grace_done	= nfsd4_cld_grace_done_v0,
> > +};
> > +
> > +/* For newer nfsdcld's */
> > +static const struct nfsd4_client_tracking_ops nfsd4_cld_tracking_ops = {
> > +	.init		= nfsd4_cld_tracking_init,
> > +	.exit		= nfsd4_cld_tracking_exit,
> > +	.create		= nfsd4_cld_create,
> > +	.remove		= nfsd4_cld_remove,
> >  	.check		= nfsd4_cld_check,
> >  	.grace_done	= nfsd4_cld_grace_done,
> >  };
> > @@ -1514,9 +1722,10 @@ nfsd4_client_tracking_init(struct net *net)
> >  
> >  	/* Finally, try to use nfsdcld */
> >  	nn->client_tracking_ops = &nfsd4_cld_tracking_ops;
> > -	printk(KERN_WARNING "NFSD: the nfsdcld client tracking upcall will be "
> > -			"removed in 3.10. Please transition to using "
> > -			"nfsdcltrack.\n");
> > +	status = nn->client_tracking_ops->init(net);
> > +	if (!status)
> > +		return status;
> > +	nn->client_tracking_ops = &nfsd4_cld_tracking_ops_v0;
> 
> It seems like we probably ought to check to see if the daemon is up
> before attempting a UMH upcall now? If someone starts up the daemon
> they'll probably be surprised that it didn't get used because there was
> a UMH upcall program present.

I figured that the UMH upcall program would still be the default and
that the admin would have to do some extra configuration to use nfsdcld,
namely remove the /var/lib/nfs/v4recovery directory and set an empty
value for nfsd's 'cltrack_prog' module option.  Do you think that's a
bad idea?

-Scott

> 
> >  do_init:
> >  	status = nn->client_tracking_ops->init(net);
> >  	if (status) {
> > diff --git a/include/uapi/linux/nfsd/cld.h b/include/uapi/linux/nfsd/cld.h
> > index f8f5cccad749..b1e9de4f07d5 100644
> > --- a/include/uapi/linux/nfsd/cld.h
> > +++ b/include/uapi/linux/nfsd/cld.h
> > @@ -36,6 +36,7 @@ enum cld_command {
> >  	Cld_Remove,		/* remove record of this cm_id */
> >  	Cld_Check,		/* is this cm_id allowed? */
> >  	Cld_GraceDone,		/* grace period is complete */
> > +	Cld_GraceStart,
> >  };
> >  
> >  /* representation of long-form NFSv4 client ID */
> 
> -- 
> Jeff Layton <jlayton@kernel.org>
>