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Date:   Wed, 5 Dec 2018 20:38:18 -0500
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Scott Mayhew <smayhew@redhat.com>
Cc:     jlayton@kernel.org, linux-nfs@vger.kernel.org
Subject: Re: [PATCH RFC 3/4] nfsd: un-deprecate nfsdcld
Message-ID: <20181206013818.GC8539@fieldses.org>
References: <20181106183511.17836-1-smayhew@redhat.com>
 <20181106183511.17836-4-smayhew@redhat.com>
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On Tue, Nov 06, 2018 at 01:35:10PM -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.

Kind of a  funny convention, but OK, sounds like it should work.

> 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).

Sounds good.

The code looks OK to me.

--b.

> 
> 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 b288b14273ff..10887fdce8c2 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -763,6 +763,34 @@ 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)
>  {
> @@ -772,6 +800,7 @@ 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,
> @@ -785,13 +814,24 @@ 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;
>  		}
>  	}
> @@ -803,6 +843,9 @@ 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;
>  
> @@ -1049,9 +1092,14 @@ 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;
> @@ -1084,8 +1132,61 @@ 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;
> @@ -1109,11 +1210,118 @@ 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,
>  };
> @@ -1498,9 +1706,10 @@ 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;
>  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 */
> -- 
> 2.17.1