[PATCH 07/12] NFS: Introduce nfs4_proc_get_mig_status()

[Chuck Lever <chuck.lever@oracle.com>]

The nfs4_proc_fs_locations() function is invoked during referral
processing to perform a GETATTR(fs_locations) on an object's parent
directory in order to discover the target of the referral.  It
performs a LOOKUP, so the client needs to know the parent's file
handle a priori.

To handle migration recovery, we need to probe fs_locations
information on an FSID's root directory.  The "parent" of the root
directory is not available via LOOKUP.

Additionally, a minor version zero server needs to know what client ID
is requesting fs_locations information, so it can clear the flag that
forces it to continue returning NFS4ERR_LEASE_MOVED.  This flag is set
per client ID and per FSID.  The client ID is not an argument of the
PUTFH or GETATTR operations.

Later minor versions have client ID information embedded in the
session ID.  By convention, minor version zero clients send a RENEW
operation in the same compound as the GETATTR(fs_locations).  (We may
need to visit this for referrals too, in case the LOOKUP operation is
actually seeing a migration).

Because of all of this, we need a new variant of
nfs4_proc_fs_locations() that can operate directly on a target file
handle, rather than taking a name and doing a LOOKUP as part of
retrieving fs_locations from the server.  It also must properly append
a RENEW operation as needed.  Introduce nfs4_proc_get_mig_status() to
fill this role, and add the requisite XDR encoding and decoding
paraphenalia.

Under the covers, both nfs4_proc_foo functions use the FS_LOCATIONS
XDR routines.  This is a little awkward, but is necessary because it's
currently not easy to add new NFSv4 procedures due to a bug in
nfsstat.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---

 fs/nfs/nfs4_fs.h        |    2 +
 fs/nfs/nfs4proc.c       |   67 ++++++++++++++++++++++++++++++++++++++++++++++-
 fs/nfs/nfs4xdr.c        |   48 +++++++++++++++++++++++++---------
 include/linux/nfs_xdr.h |    7 ++++-
 4 files changed, 108 insertions(+), 16 deletions(-)

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index e266e2d..b746a51 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -241,6 +241,8 @@ extern int nfs4_do_close(struct path *path, struct nfs4_state *state, gfp_t gfp_
 extern int nfs4_server_capabilities(struct nfs_server *server, struct nfs_fh *fhandle);
 extern int nfs4_proc_fs_locations(struct inode *dir, const struct qstr *name,
 		struct nfs4_fs_locations *fs_locations, struct page *page);
+extern int nfs4_proc_get_mig_status(struct nfs_server *server,
+		struct nfs4_fs_locations *fs_locations, struct page *page);
 extern void nfs4_release_lockowner(const struct nfs4_lock_state *);
 extern const struct xattr_handler *nfs4_xattr_handlers[];
 
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 1e72e5f..bdd8aac 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4527,6 +4527,16 @@ static void nfs_fixup_referral_attributes(struct nfs_fattr *fattr)
 	fattr->nlink = 2;
 }
 
+/**
+ * nfs4_proc_fs_locations - retrieve locations array for a named object
+ *
+ * @dir: inode of parent directory
+ * @name: qstr containing name of object to query
+ * @locations: result of query
+ * @page: buffer
+ *
+ * Returns zero on success, or a negative errno code
+ */
 int nfs4_proc_fs_locations(struct inode *dir, const struct qstr *name,
 		struct nfs4_fs_locations *fs_locations, struct page *page)
 {
@@ -4551,13 +4561,66 @@ int nfs4_proc_fs_locations(struct inode *dir, const struct qstr *name,
 	};
 	int status;
 
-	dprintk("%s: start\n", __func__);
+	dprintk("--> %s: FSID %llx:%llx on \"%s\"\n", __func__,
+		(unsigned long long)server->fsid.major,
+		(unsigned long long)server->fsid.minor,
+		server->nfs_client->cl_hostname);
 	nfs_fattr_init(&fs_locations->fattr);
 	fs_locations->server = server;
 	fs_locations->nlocations = 0;
 	status = nfs4_call_sync(server, &msg, &args, &res, 0);
 	nfs_fixup_referral_attributes(&fs_locations->fattr);
-	dprintk("%s: returned status = %d\n", __func__, status);
+	dprintk("<-- %s status=%d\n", __func__, status);
+	return status;
+}
+
+/**
+ * nfs4_proc_get_mig_status - probe migration status of an export
+ *
+ * @server: local state for server
+ * @locations: result of query
+ * @page: buffer
+ *
+ * Returns zero on success, or a negative errno code
+ */
+int nfs4_proc_get_mig_status(struct nfs_server *server,
+			     struct nfs4_fs_locations *locations,
+			     struct page *page)
+{
+	u32 bitmask[2] = {
+		[0]		= FATTR4_WORD0_FSID |
+				  FATTR4_WORD0_FS_LOCATIONS,
+	};
+	struct nfs4_fs_locations_arg args = {
+		.client		= server->nfs_client,
+		.fh		= server->rootfh,
+		.page		= page,
+		.bitmask	= bitmask,
+	};
+	struct nfs4_fs_locations_res res = {
+		.fs_locations	= locations,
+	};
+	struct rpc_message msg = {
+		.rpc_proc	= &nfs4_procedures[NFSPROC4_CLNT_FS_LOCATIONS],
+		.rpc_argp	= &args,
+		.rpc_resp	= &res,
+	};
+	int status;
+
+	dprintk("--> %s: FSID %llx:%llx on \"%s\"\n", __func__,
+		(unsigned long long)server->fsid.major,
+		(unsigned long long)server->fsid.minor,
+		args.client->cl_hostname);
+	nfs_display_fhandle(args.fh, "Probing file handle");
+
+	args.mig_status = res.mig_status = 1;
+	if (args.client->cl_mvops->minor_version == 0)
+		args.renew = res.renew = 1;
+	nfs_fattr_init(&locations->fattr);
+	locations->server = server;
+	locations->nlocations = 0;
+	status = nfs4_call_sync(server, &msg, &args, &res, 0);
+	dprintk("<-- %s status=%d\n", __func__, status);
 	return status;
 }
 
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 9d2c9d2..e4a8e50 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -669,13 +669,15 @@ static int nfs4_stat_to_errno(int);
 				 encode_sequence_maxsz + \
 				 encode_putfh_maxsz + \
 				 encode_lookup_maxsz + \
-				 encode_fs_locations_maxsz)
+				 encode_fs_locations_maxsz + \
+				 encode_renew_maxsz)
 #define NFS4_dec_fs_locations_sz \
 				(compound_decode_hdr_maxsz + \
 				 decode_sequence_maxsz + \
 				 decode_putfh_maxsz + \
 				 decode_lookup_maxsz + \
-				 decode_fs_locations_maxsz)
+				 decode_fs_locations_maxsz + \
+				 encode_renew_maxsz)
 #if defined(CONFIG_NFS_V4_1)
 #define NFS4_enc_exchange_id_sz \
 				(compound_encode_hdr_maxsz + \
@@ -2450,11 +2452,20 @@ static void nfs4_xdr_enc_fs_locations(struct rpc_rqst *req,
 
 	encode_compound_hdr(xdr, req, &hdr);
 	encode_sequence(xdr, &args->seq_args, &hdr);
-	encode_putfh(xdr, args->dir_fh, &hdr);
-	encode_lookup(xdr, args->name, &hdr);
-	replen = hdr.replen;	/* get the attribute into args->page */
-	encode_fs_locations(xdr, args->bitmask, &hdr);
+	if (args->mig_status) {
+		encode_putfh(xdr, args->fh, &hdr);
+		replen = hdr.replen;
+		encode_fs_locations(xdr, args->bitmask, &hdr);
+		if (args->renew)
+			encode_renew(xdr, args->client, &hdr);
+	} else {
+		encode_putfh(xdr, args->dir_fh, &hdr);
+		encode_lookup(xdr, args->name, &hdr);
+		replen = hdr.replen;
+		encode_fs_locations(xdr, args->bitmask, &hdr);
+	}
 
+	/* Set up reply kvec to capture returned fs_locations array. */
 	xdr_inline_pages(&req->rq_rcv_buf, replen << 2, &args->page,
 			0, PAGE_SIZE);
 	encode_nops(&hdr);
@@ -5904,13 +5915,24 @@ static int nfs4_xdr_dec_fs_locations(struct rpc_rqst *req,
 	status = decode_putfh(xdr);
 	if (status)
 		goto out;
-	status = decode_lookup(xdr);
-	if (status)
-		goto out;
-	xdr_enter_page(xdr, PAGE_SIZE);
-	status = decode_getfattr(xdr, &res->fs_locations->fattr,
-				 res->fs_locations->server,
-				 !RPC_IS_ASYNC(req->rq_task));
+	if (res->mig_status) {
+		xdr_enter_page(xdr, PAGE_SIZE);
+		status = decode_getfattr(xdr, &res->fs_locations->fattr,
+				 	res->fs_locations->server,
+				 	!RPC_IS_ASYNC(req->rq_task));
+		if (status)
+			goto out;
+		if (res->renew)
+			status = decode_renew(xdr);
+	} else {
+		status = decode_lookup(xdr);
+		if (status)
+			goto out;
+		xdr_enter_page(xdr, PAGE_SIZE);
+		status = decode_getfattr(xdr, &res->fs_locations->fattr,
+				 	res->fs_locations->server,
+				 	!RPC_IS_ASYNC(req->rq_task));
+	}
 out:
 	return status;
 }
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 2492487..bcf823b 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -925,16 +925,21 @@ struct nfs4_fs_locations {
 };
 
 struct nfs4_fs_locations_arg {
+	const struct nfs_client *client;
 	const struct nfs_fh *dir_fh;
+	const struct nfs_fh *fh;
 	const struct qstr *name;
 	struct page *page;
 	const u32 *bitmask;
-	struct nfs4_sequence_args	seq_args;
+	struct nfs4_sequence_args seq_args;
+	unsigned char mig_status : 1, renew : 1;
 };
 
 struct nfs4_fs_locations_res {
 	struct nfs4_fs_locations       *fs_locations;
 	struct nfs4_sequence_res	seq_res;
+	unsigned char			mig_status : 1,
+					renew : 1;
 };
 
 #endif /* CONFIG_NFS_V4 */