flexfiles: use per-mirror specified stateid for IO

rfc8435 says:

  For tight coupling, ffds_stateid provides the stateid to be used by
  the client to access the file.

However current implementation replaces per-mirror provided stateid with
by open or lock stateid.

Ensure that per-mirror stateid is used by ff_layout_write_prepare_v4 and
nfs4_ff_layout_prepare_ds.
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -1361,12 +1361,7 @@ static void ff_layout_read_prepare_v4(struct rpc_task *task, void *data)
 				task))
 		return;
 
-	if (ff_layout_read_prepare_common(task, hdr))
-		return;
-
-	if (nfs4_set_rw_stateid(&hdr->args.stateid, hdr->args.context,
-			hdr->args.lock_context, FMODE_READ) == -EIO)
-		rpc_exit(task, -EIO); /* lost lock, terminate I/O */
+	ff_layout_read_prepare_common(task, hdr);
 }
 
 static void ff_layout_read_call_done(struct rpc_task *task, void *data)
@@ -1542,12 +1537,7 @@ static void ff_layout_write_prepare_v4(struct rpc_task *task, void *data)
 				task))
 		return;
 
-	if (ff_layout_write_prepare_common(task, hdr))
-		return;
-
-	if (nfs4_set_rw_stateid(&hdr->args.stateid, hdr->args.context,
-			hdr->args.lock_context, FMODE_WRITE) == -EIO)
-		rpc_exit(task, -EIO); /* lost lock, terminate I/O */
+	ff_layout_write_prepare_common(task, hdr);
 }
 
 static void ff_layout_write_call_done(struct rpc_task *task, void *data)
@@ -1742,6 +1732,10 @@ ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
 	fh = nfs4_ff_layout_select_ds_fh(lseg, idx);
 	if (fh)
 		hdr->args.fh = fh;
+
+	if (!nfs4_ff_layout_select_ds_stateid(lseg, idx, &hdr->args.stateid))
+		goto out_failed;
+
 	/*
 	 * Note that if we ever decide to split across DSes,
 	 * then we may need to handle dense-like offsets.
@@ -1804,6 +1798,9 @@ ff_layout_write_pagelist(struct nfs_pgio_header *hdr, int sync)
 	if (fh)
 		hdr->args.fh = fh;
 
+	if (!nfs4_ff_layout_select_ds_stateid(lseg, idx, &hdr->args.stateid))
+		goto out_failed;
+
 	/*
 	 * Note that if we ever decide to split across DSes,
 	 * then we may need to handle dense-like offsets.

fs/nfs/flexfilelayout/flexfilelayout.h

@@ -215,6 +215,10 @@ unsigned int ff_layout_fetch_ds_ioerr(struct pnfs_layout_hdr *lo,
 		unsigned int maxnum);
 struct nfs_fh *
 nfs4_ff_layout_select_ds_fh(struct pnfs_layout_segment *lseg, u32 mirror_idx);
+int
+nfs4_ff_layout_select_ds_stateid(struct pnfs_layout_segment *lseg,
+				u32 mirror_idx,
+				nfs4_stateid *stateid);
 
 struct nfs4_pnfs_ds *
 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx,

fs/nfs/flexfilelayout/flexfilelayoutdev.c

@@ -370,6 +370,25 @@ nfs4_ff_layout_select_ds_fh(struct pnfs_layout_segment *lseg, u32 mirror_idx)
 	return fh;
 }
 
+int
+nfs4_ff_layout_select_ds_stateid(struct pnfs_layout_segment *lseg,
+				u32 mirror_idx,
+				nfs4_stateid *stateid)
+{
+	struct nfs4_ff_layout_mirror *mirror = FF_LAYOUT_COMP(lseg, mirror_idx);
+
+	if (!ff_layout_mirror_valid(lseg, mirror, false)) {
+		pr_err_ratelimited("NFS: %s: No data server for mirror offset index %d\n",
+			__func__, mirror_idx);
+		goto out;
+	}
+
+	nfs4_stateid_copy(stateid, &mirror->stateid);
+	return 1;
+out:
+	return 0;
+}
+
 /**
  * nfs4_ff_layout_prepare_ds - prepare a DS connection for an RPC call
  * @lseg: the layout segment we're operating on