nfsd: implement pNFS layout recalls

Add support to issue layout recalls to clients.  For now we only support
full-file recalls to get a simple and stable implementation.  This allows
to embedd a nfsd4_callback structure in the layout_state and thus avoid
any memory allocations under spinlocks during a recall.  For normal
use cases that do not intent to share a single file between multiple
clients this implementation is fully sufficient.

To ensure layouts are recalled on local filesystem access each layout
state registers a new FL_LAYOUT lease with the kernel file locking code,
which filesystems that support pNFS exports that require recalls need
to break on conflicting access patterns.

The XDR code is based on the old pNFS server implementation by
Andy Adamson, Benny Halevy, Boaz Harrosh, Dean Hildebrand, Fred Isaman,
Marc Eshel, Mike Sager and Ricardo Labiaga.

Signed-off-by: Christoph Hellwig <hch@lst.de>

fs/nfsd/nfs4callback.c

@@ -546,6 +546,102 @@ out:
 	return status;
 }
 
+#ifdef CONFIG_NFSD_PNFS
+/*
+ * CB_LAYOUTRECALL4args
+ *
+ *	struct layoutrecall_file4 {
+ *		nfs_fh4         lor_fh;
+ *		offset4         lor_offset;
+ *		length4         lor_length;
+ *		stateid4        lor_stateid;
+ *	};
+ *
+ *	union layoutrecall4 switch(layoutrecall_type4 lor_recalltype) {
+ *	case LAYOUTRECALL4_FILE:
+ *		layoutrecall_file4 lor_layout;
+ *	case LAYOUTRECALL4_FSID:
+ *		fsid4              lor_fsid;
+ *	case LAYOUTRECALL4_ALL:
+ *		void;
+ *	};
+ *
+ *	struct CB_LAYOUTRECALL4args {
+ *		layouttype4             clora_type;
+ *		layoutiomode4           clora_iomode;
+ *		bool                    clora_changed;
+ *		layoutrecall4           clora_recall;
+ *	};
+ */
+static void encode_cb_layout4args(struct xdr_stream *xdr,
+				  const struct nfs4_layout_stateid *ls,
+				  struct nfs4_cb_compound_hdr *hdr)
+{
+	__be32 *p;
+
+	BUG_ON(hdr->minorversion == 0);
+
+	p = xdr_reserve_space(xdr, 5 * 4);
+	*p++ = cpu_to_be32(OP_CB_LAYOUTRECALL);
+	*p++ = cpu_to_be32(ls->ls_layout_type);
+	*p++ = cpu_to_be32(IOMODE_ANY);
+	*p++ = cpu_to_be32(1);
+	*p = cpu_to_be32(RETURN_FILE);
+
+	encode_nfs_fh4(xdr, &ls->ls_stid.sc_file->fi_fhandle);
+
+	p = xdr_reserve_space(xdr, 2 * 8);
+	p = xdr_encode_hyper(p, 0);
+	xdr_encode_hyper(p, NFS4_MAX_UINT64);
+
+	encode_stateid4(xdr, &ls->ls_recall_sid);
+
+	hdr->nops++;
+}
+
+static void nfs4_xdr_enc_cb_layout(struct rpc_rqst *req,
+				   struct xdr_stream *xdr,
+				   const struct nfsd4_callback *cb)
+{
+	const struct nfs4_layout_stateid *ls =
+		container_of(cb, struct nfs4_layout_stateid, ls_recall);
+	struct nfs4_cb_compound_hdr hdr = {
+		.ident = 0,
+		.minorversion = cb->cb_minorversion,
+	};
+
+	encode_cb_compound4args(xdr, &hdr);
+	encode_cb_sequence4args(xdr, cb, &hdr);
+	encode_cb_layout4args(xdr, ls, &hdr);
+	encode_cb_nops(&hdr);
+}
+
+static int nfs4_xdr_dec_cb_layout(struct rpc_rqst *rqstp,
+				  struct xdr_stream *xdr,
+				  struct nfsd4_callback *cb)
+{
+	struct nfs4_cb_compound_hdr hdr;
+	enum nfsstat4 nfserr;
+	int status;
+
+	status = decode_cb_compound4res(xdr, &hdr);
+	if (unlikely(status))
+		goto out;
+	if (cb) {
+		status = decode_cb_sequence4res(xdr, cb);
+		if (unlikely(status))
+			goto out;
+	}
+	status = decode_cb_op_status(xdr, OP_CB_LAYOUTRECALL, &nfserr);
+	if (unlikely(status))
+		goto out;
+	if (unlikely(nfserr != NFS4_OK))
+		status = nfs_cb_stat_to_errno(nfserr);
+out:
+	return status;
+}
+#endif /* CONFIG_NFSD_PNFS */
+
 /*
  * RPC procedure tables
  */
@@ -563,6 +659,9 @@ out:
 static struct rpc_procinfo nfs4_cb_procedures[] = {
 	PROC(CB_NULL,	NULL,		cb_null,	cb_null),
 	PROC(CB_RECALL,	COMPOUND,	cb_recall,	cb_recall),
+#ifdef CONFIG_NFSD_PNFS
+	PROC(CB_LAYOUT,	COMPOUND,	cb_layout,	cb_layout),
+#endif
 };
 
 static struct rpc_version nfs_cb_version4 = {

fs/nfsd/nfs4layouts.c

@@ -1,8 +1,11 @@
 /*
  * Copyright (c) 2014 Christoph Hellwig.
  */
+#include <linux/kmod.h>
+#include <linux/file.h>
 #include <linux/jhash.h>
 #include <linux/sched.h>
+#include <linux/sunrpc/addr.h>
 
 #include "pnfs.h"
 #include "netns.h"
@@ -18,6 +21,9 @@ struct nfs4_layout {
 static struct kmem_cache *nfs4_layout_cache;
 static struct kmem_cache *nfs4_layout_stateid_cache;
 
+static struct nfsd4_callback_ops nfsd4_cb_layout_ops;
+static const struct lock_manager_operations nfsd4_layouts_lm_ops;
+
 const struct nfsd4_layout_ops *nfsd4_layout_ops[LAYOUT_TYPE_MAX] =  {
 };
 
@@ -127,9 +133,42 @@ nfsd4_free_layout_stateid(struct nfs4_stid *stid)
 	list_del_init(&ls->ls_perfile);
 	spin_unlock(&fp->fi_lock);
 
+	vfs_setlease(ls->ls_file, F_UNLCK, NULL, (void **)&ls);
+	fput(ls->ls_file);
+
+	if (ls->ls_recalled)
+		atomic_dec(&ls->ls_stid.sc_file->fi_lo_recalls);
+
 	kmem_cache_free(nfs4_layout_stateid_cache, ls);
 }
 
+static int
+nfsd4_layout_setlease(struct nfs4_layout_stateid *ls)
+{
+	struct file_lock *fl;
+	int status;
+
+	fl = locks_alloc_lock();
+	if (!fl)
+		return -ENOMEM;
+	locks_init_lock(fl);
+	fl->fl_lmops = &nfsd4_layouts_lm_ops;
+	fl->fl_flags = FL_LAYOUT;
+	fl->fl_type = F_RDLCK;
+	fl->fl_end = OFFSET_MAX;
+	fl->fl_owner = ls;
+	fl->fl_pid = current->tgid;
+	fl->fl_file = ls->ls_file;
+
+	status = vfs_setlease(fl->fl_file, fl->fl_type, &fl, NULL);
+	if (status) {
+		locks_free_lock(fl);
+		return status;
+	}
+	BUG_ON(fl != NULL);
+	return 0;
+}
+
 static struct nfs4_layout_stateid *
 nfsd4_alloc_layout_stateid(struct nfsd4_compound_state *cstate,
 		struct nfs4_stid *parent, u32 layout_type)
@@ -152,6 +191,20 @@ nfsd4_alloc_layout_stateid(struct nfsd4_compound_state *cstate,
 	spin_lock_init(&ls->ls_lock);
 	INIT_LIST_HEAD(&ls->ls_layouts);
 	ls->ls_layout_type = layout_type;
+	nfsd4_init_cb(&ls->ls_recall, clp, &nfsd4_cb_layout_ops,
+			NFSPROC4_CLNT_CB_LAYOUT);
+
+	if (parent->sc_type == NFS4_DELEG_STID)
+		ls->ls_file = get_file(fp->fi_deleg_file);
+	else
+		ls->ls_file = find_any_file(fp);
+	BUG_ON(!ls->ls_file);
+
+	if (nfsd4_layout_setlease(ls)) {
+		put_nfs4_file(fp);
+		kmem_cache_free(nfs4_layout_stateid_cache, ls);
+		return NULL;
+	}
 
 	spin_lock(&clp->cl_lock);
 	stp->sc_type = NFS4_LAYOUT_STID;
@@ -215,6 +268,27 @@ out:
 	return status;
 }
 
+static void
+nfsd4_recall_file_layout(struct nfs4_layout_stateid *ls)
+{
+	spin_lock(&ls->ls_lock);
+	if (ls->ls_recalled)
+		goto out_unlock;
+
+	ls->ls_recalled = true;
+	atomic_inc(&ls->ls_stid.sc_file->fi_lo_recalls);
+	if (list_empty(&ls->ls_layouts))
+		goto out_unlock;
+
+	atomic_inc(&ls->ls_stid.sc_count);
+	update_stateid(&ls->ls_stid.sc_stateid);
+	memcpy(&ls->ls_recall_sid, &ls->ls_stid.sc_stateid, sizeof(stateid_t));
+	nfsd4_run_cb(&ls->ls_recall);
+
+out_unlock:
+	spin_unlock(&ls->ls_lock);
+}
+
 static inline u64
 layout_end(struct nfsd4_layout_seg *seg)
 {
@@ -258,18 +332,44 @@ layouts_try_merge(struct nfsd4_layout_seg *lo, struct nfsd4_layout_seg *new)
 	return true;
 }
 
+static __be32
+nfsd4_recall_conflict(struct nfs4_layout_stateid *ls)
+{
+	struct nfs4_file *fp = ls->ls_stid.sc_file;
+	struct nfs4_layout_stateid *l, *n;
+	__be32 nfserr = nfs_ok;
+
+	assert_spin_locked(&fp->fi_lock);
+
+	list_for_each_entry_safe(l, n, &fp->fi_lo_states, ls_perfile) {
+		if (l != ls) {
+			nfsd4_recall_file_layout(l);
+			nfserr = nfserr_recallconflict;
+		}
+	}
+
+	return nfserr;
+}
+
 __be32
 nfsd4_insert_layout(struct nfsd4_layoutget *lgp, struct nfs4_layout_stateid *ls)
 {
 	struct nfsd4_layout_seg *seg = &lgp->lg_seg;
+	struct nfs4_file *fp = ls->ls_stid.sc_file;
 	struct nfs4_layout *lp, *new = NULL;
+	__be32 nfserr;
 
+	spin_lock(&fp->fi_lock);
+	nfserr = nfsd4_recall_conflict(ls);
+	if (nfserr)
+		goto out;
 	spin_lock(&ls->ls_lock);
 	list_for_each_entry(lp, &ls->ls_layouts, lo_perstate) {
 		if (layouts_try_merge(&lp->lo_seg, seg))
 			goto done;
 	}
 	spin_unlock(&ls->ls_lock);
+	spin_unlock(&fp->fi_lock);
 
 	new = kmem_cache_alloc(nfs4_layout_cache, GFP_KERNEL);
 	if (!new)
@@ -277,6 +377,10 @@ nfsd4_insert_layout(struct nfsd4_layoutget *lgp, struct nfs4_layout_stateid *ls)
 	memcpy(&new->lo_seg, seg, sizeof(lp->lo_seg));
 	new->lo_state = ls;
 
+	spin_lock(&fp->fi_lock);
+	nfserr = nfsd4_recall_conflict(ls);
+	if (nfserr)
+		goto out;
 	spin_lock(&ls->ls_lock);
 	list_for_each_entry(lp, &ls->ls_layouts, lo_perstate) {
 		if (layouts_try_merge(&lp->lo_seg, seg))
@@ -290,9 +394,11 @@ done:
 	update_stateid(&ls->ls_stid.sc_stateid);
 	memcpy(&lgp->lg_sid, &ls->ls_stid.sc_stateid, sizeof(stateid_t));
 	spin_unlock(&ls->ls_lock);
+out:
+	spin_unlock(&fp->fi_lock);
 	if (new)
 		kmem_cache_free(nfs4_layout_cache, new);
-	return nfs_ok;
+	return nfserr;
 }
 
 static void
@@ -448,6 +554,112 @@ nfsd4_return_all_file_layouts(struct nfs4_client *clp, struct nfs4_file *fp)
 	nfsd4_free_layouts(&reaplist);
 }
 
+static void
+nfsd4_cb_layout_fail(struct nfs4_layout_stateid *ls)
+{
+	struct nfs4_client *clp = ls->ls_stid.sc_client;
+	char addr_str[INET6_ADDRSTRLEN];
+	static char *envp[] = {
+		"HOME=/",
+		"TERM=linux",
+		"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
+		NULL
+	};
+	char *argv[8];
+	int error;
+
+	rpc_ntop((struct sockaddr *)&clp->cl_addr, addr_str, sizeof(addr_str));
+
+	printk(KERN_WARNING
+		"nfsd: client %s failed to respond to layout recall. "
+		"  Fencing..\n", addr_str);
+
+	argv[0] = "/sbin/nfsd-recall-failed";
+	argv[1] = addr_str;
+	argv[2] = ls->ls_file->f_path.mnt->mnt_sb->s_id;
+	argv[3] = NULL;
+
+	error = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
+	if (error) {
+		printk(KERN_ERR "nfsd: fence failed for client %s: %d!\n",
+			addr_str, error);
+	}
+}
+
+static int
+nfsd4_cb_layout_done(struct nfsd4_callback *cb, struct rpc_task *task)
+{
+	struct nfs4_layout_stateid *ls =
+		container_of(cb, struct nfs4_layout_stateid, ls_recall);
+	LIST_HEAD(reaplist);
+
+	switch (task->tk_status) {
+	case 0:
+		return 1;
+	case -NFS4ERR_NOMATCHING_LAYOUT:
+		task->tk_status = 0;
+		return 1;
+	case -NFS4ERR_DELAY:
+		/* Poll the client until it's done with the layout */
+		/* FIXME: cap number of retries.
+		 * The pnfs standard states that we need to only expire
+		 * the client after at-least "lease time" .eg lease-time * 2
+		 * when failing to communicate a recall
+		 */
+		rpc_delay(task, HZ/100); /* 10 mili-seconds */
+		return 0;
+	default:
+		/*
+		 * Unknown error or non-responding client, we'll need to fence.
+		 */
+		nfsd4_cb_layout_fail(ls);
+		return -1;
+	}
+}
+
+static void
+nfsd4_cb_layout_release(struct nfsd4_callback *cb)
+{
+	struct nfs4_layout_stateid *ls =
+		container_of(cb, struct nfs4_layout_stateid, ls_recall);
+	LIST_HEAD(reaplist);
+
+	nfsd4_return_all_layouts(ls, &reaplist);
+	nfsd4_free_layouts(&reaplist);
+	nfs4_put_stid(&ls->ls_stid);
+}
+
+static struct nfsd4_callback_ops nfsd4_cb_layout_ops = {
+	.done		= nfsd4_cb_layout_done,
+	.release	= nfsd4_cb_layout_release,
+};
+
+static bool
+nfsd4_layout_lm_break(struct file_lock *fl)
+{
+	/*
+	 * We don't want the locks code to timeout the lease for us;
+	 * we'll remove it ourself if a layout isn't returned
+	 * in time:
+	 */
+	fl->fl_break_time = 0;
+	nfsd4_recall_file_layout(fl->fl_owner);
+	return false;
+}
+
+static int
+nfsd4_layout_lm_change(struct file_lock *onlist, int arg,
+		struct list_head *dispose)
+{
+	BUG_ON(!(arg & F_UNLCK));
+	return lease_modify(onlist, arg, dispose);
+}
+
+static const struct lock_manager_operations nfsd4_layouts_lm_ops = {
+	.lm_break	= nfsd4_layout_lm_break,
+	.lm_change	= nfsd4_layout_lm_change,
+};
+
 int
 nfsd4_init_pnfs(void)
 {

fs/nfsd/nfs4proc.c

@@ -1301,6 +1301,10 @@ nfsd4_layoutget(struct svc_rqst *rqstp,
 	if (nfserr)
 		goto out;
 
+	nfserr = nfserr_recallconflict;
+	if (atomic_read(&ls->ls_stid.sc_file->fi_lo_recalls))
+		goto out_put_stid;
+
 	nfserr = ops->proc_layoutget(current_fh->fh_dentry->d_inode,
 				     current_fh, lgp);
 	if (nfserr)

fs/nfsd/nfs4state.c

@@ -3065,6 +3065,7 @@ static void nfsd4_init_file(struct knfsd_fh *fh, unsigned int hashval,
 	memset(fp->fi_access, 0, sizeof(fp->fi_access));
 #ifdef CONFIG_NFSD_PNFS
 	INIT_LIST_HEAD(&fp->fi_lo_states);
+	atomic_set(&fp->fi_lo_recalls, 0);
 #endif
 	hlist_add_head_rcu(&fp->fi_hash, &file_hashtbl[hashval]);
 }

fs/nfsd/state.h

@@ -502,6 +502,7 @@ struct nfs4_file {
 	bool			fi_had_conflict;
 #ifdef CONFIG_NFSD_PNFS
 	struct list_head	fi_lo_states;
+	atomic_t		fi_lo_recalls;
 #endif
 };
 
@@ -542,6 +543,10 @@ struct nfs4_layout_stateid {
 	spinlock_t			ls_lock;
 	struct list_head		ls_layouts;
 	u32				ls_layout_type;
+	struct file			*ls_file;
+	struct nfsd4_callback		ls_recall;
+	stateid_t			ls_recall_sid;
+	bool				ls_recalled;
 };
 
 static inline struct nfs4_layout_stateid *layoutstateid(struct nfs4_stid *s)
@@ -556,6 +561,7 @@ static inline struct nfs4_layout_stateid *layoutstateid(struct nfs4_stid *s)
 enum nfsd4_cb_op {
 	NFSPROC4_CLNT_CB_NULL = 0,
 	NFSPROC4_CLNT_CB_RECALL,
+	NFSPROC4_CLNT_CB_LAYOUT,
 	NFSPROC4_CLNT_CB_SEQUENCE,
 };
 

fs/nfsd/xdr4cb.h

@@ -21,3 +21,10 @@
 #define NFS4_dec_cb_recall_sz		(cb_compound_dec_hdr_sz  +      \
 					cb_sequence_dec_sz +            \
 					op_dec_sz)
+#define NFS4_enc_cb_layout_sz		(cb_compound_enc_hdr_sz +       \
+					cb_sequence_enc_sz +            \
+					1 + 3 +                         \
+					enc_nfs4_fh_sz + 4)
+#define NFS4_dec_cb_layout_sz		(cb_compound_dec_hdr_sz  +      \
+					cb_sequence_dec_sz +            \
+					op_dec_sz)