nfsv41/pnfsblock: allow block client not to layoutget in pg_init

index baf7353..3be29c7 100644
@@ -848,7 +848,7 @@ alloc_init_layout_hdr(struct inode *ino,
 	return lo;
 }
 
-static struct pnfs_layout_hdr *
+struct pnfs_layout_hdr *
 pnfs_find_alloc_layout(struct inode *ino,
 		       struct nfs_open_context *ctx,
 		       gfp_t gfp_flags)

@@ -875,6 +875,7 @@ pnfs_find_alloc_layout(struct inode *ino,
 		pnfs_free_layout_hdr(new);
 	return nfsi->layout;
 }
+EXPORT_SYMBOL_GPL(pnfs_find_alloc_layout);
 
 /*
  * iomode matching rules:

index 1509530..9614ac9 100644
@@ -209,6 +209,10 @@ struct pnfs_layout_segment *pnfs_update_layout(struct inode *ino,
 					       u64 count,
 					       enum pnfs_iomode iomode,
 					       gfp_t gfp_flags);
+struct pnfs_layout_hdr *
+pnfs_find_alloc_layout(struct inode *ino,
+		       struct nfs_open_context *ctx,
+		       gfp_t gfp_flags);
 
 void nfs4_deviceid_mark_client_invalid(struct nfs_client *clp);
 

index 3be29c7..734e670 100644
@@ -933,6 +933,31 @@ pnfs_find_lseg(struct pnfs_layout_hdr *lo,
 }
 
 /*
+ * Find and reference lseg with ino->i_lock held.
+ */
+struct pnfs_layout_segment *
+pnfs_find_get_layout_locked(struct inode *ino,
+			loff_t pos,
+			u64 count,
+			enum pnfs_iomode iomode)
+{
+	struct pnfs_layout_segment *lseg = NULL;
+	struct pnfs_layout_range range = {
+		.iomode = iomode,
+		.offset = pos,
+		.length = count,
+	};
+
+	if (NFS_I(ino)->layout == NULL)
+		goto out;
+
+	lseg = pnfs_find_lseg(NFS_I(ino)->layout, &range);
+out:
+	return lseg;
+}
+EXPORT_SYMBOL_GPL(pnfs_find_get_layout_locked);
+
+/*
  * Layout segment is retreived from the server if not cached.
  * The appropriate layout segment is referenced and returned to the caller.
  */

index 9614ac9..0c55fc1 100644
@@ -213,6 +213,11 @@ struct pnfs_layout_hdr *
 pnfs_find_alloc_layout(struct inode *ino,
 		       struct nfs_open_context *ctx,
 		       gfp_t gfp_flags);
+struct pnfs_layout_segment *
+pnfs_find_get_layout_locked(struct inode *ino,
+			loff_t pos,
+			u64 count,
+			enum pnfs_iomode iomode);
 
 void nfs4_deviceid_mark_client_invalid(struct nfs_client *clp);
 

index 734e670..c8dc0b1 100644
@@ -1254,6 +1254,7 @@ pnfs_do_multiple_writes(struct nfs_pageio_descriptor *desc, struct list_head *he
 	struct nfs_write_data *data;
 	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
 	struct pnfs_layout_segment *lseg = desc->pg_lseg;
+	const bool has_lseg = !!lseg;
 
 	desc->pg_lseg = NULL;
 	while (!list_empty(head)) {

@@ -1262,7 +1263,29 @@ pnfs_do_multiple_writes(struct nfs_pageio_descriptor *desc, struct list_head *he
 		data = list_entry(head->next, struct nfs_write_data, list);
 		list_del_init(&data->list);
 
+		if (!has_lseg) {
+			struct nfs_page *req = nfs_list_entry(data->pages.next);
+			__u64 length = data->npages << PAGE_CACHE_SHIFT;
+
+			lseg = pnfs_update_layout(desc->pg_inode,
+						  req->wb_context,
+						  req_offset(req),
+						  length,
+						  IOMODE_RW,
+						  GFP_NOFS);
+			if (!lseg || length > (lseg->pls_range.length)) {
+				put_lseg(lseg);
+				lseg = NULL;
+				pnfs_write_through_mds(desc, data);
+				continue;
+			}
+		}
+
 		trypnfs = pnfs_try_to_write_data(data, call_ops, lseg, how);
+		if (!has_lseg) {
+			put_lseg(lseg);
+			lseg = NULL;
+		}
 		if (trypnfs == PNFS_NOT_ATTEMPTED)
 			pnfs_write_through_mds(desc, data);
 	}

@@ -1350,6 +1373,7 @@ pnfs_do_multiple_reads(struct nfs_pageio_descriptor *desc, struct list_head *hea
 	struct nfs_read_data *data;
 	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
 	struct pnfs_layout_segment *lseg = desc->pg_lseg;
+	const bool has_lseg = !!lseg;
 
 	desc->pg_lseg = NULL;
 	while (!list_empty(head)) {

@@ -1358,7 +1382,29 @@ pnfs_do_multiple_reads(struct nfs_pageio_descriptor *desc, struct list_head *hea
 		data = list_entry(head->next, struct nfs_read_data, list);
 		list_del_init(&data->list);
 
+		if (!has_lseg) {
+			struct nfs_page *req = nfs_list_entry(data->pages.next);
+			__u64 length = data->npages << PAGE_CACHE_SHIFT;
+
+			lseg = pnfs_update_layout(desc->pg_inode,
+						  req->wb_context,
+						  req_offset(req),
+						  length,
+						  IOMODE_READ,
+						  GFP_KERNEL);
+			if (!lseg || length > lseg->pls_range.length) {
+				put_lseg(lseg);
+				lseg = NULL;
+				pnfs_read_through_mds(desc, data);
+				continue;
+			}
+		}
+
 		trypnfs = pnfs_try_to_read_data(data, call_ops, lseg);
+		if (!has_lseg) {
+			put_lseg(lseg);
+			lseg = NULL;
+		}
 		if (trypnfs == PNFS_NOT_ATTEMPTED)
 			pnfs_read_through_mds(desc, data);
 	}

index 48cfac3..fd585fe 100644
@@ -39,6 +39,7 @@
 #include <linux/prefetch.h>
 
 #include "blocklayout.h"
+#include "../internal.h"
 
 #define NFSDBG_FACILITY	NFSDBG_PNFS_LD
 

@@ -990,14 +991,63 @@ bl_clear_layoutdriver(struct nfs_server *server)
 	return 0;
 }
 
+/* While RFC doesn't limit maximum size of layout, we better limit ourself. */
+#define PNFSBLK_MAXRSIZE (0x1<<22)
+#define PNFSBLK_MAXWSIZE (0x1<<21)
+static void
+bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+	struct inode *ino = pgio->pg_inode;
+	struct pnfs_layout_hdr *lo;
+
+	BUG_ON(pgio->pg_lseg != NULL);
+	spin_lock(&ino->i_lock);
+	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_KERNEL);
+	if (!lo || test_bit(lo_fail_bit(IOMODE_READ), &lo->plh_flags)) {
+		spin_unlock(&ino->i_lock);
+		nfs_pageio_reset_read_mds(pgio);
+		return;
+	}
+
+	pgio->pg_bsize = PNFSBLK_MAXRSIZE;
+	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
+						req_offset(req),
+						req->wb_bytes,
+						IOMODE_READ);
+	spin_unlock(&ino->i_lock);
+}
+
+static void
+bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+	struct inode *ino = pgio->pg_inode;
+	struct pnfs_layout_hdr *lo;
+
+	BUG_ON(pgio->pg_lseg != NULL);
+	spin_lock(&ino->i_lock);
+	lo = pnfs_find_alloc_layout(ino, req->wb_context, GFP_NOFS);
+	if (!lo || test_bit(lo_fail_bit(IOMODE_RW), &lo->plh_flags)) {
+		spin_unlock(&ino->i_lock);
+		nfs_pageio_reset_write_mds(pgio);
+		return;
+	}
+
+	pgio->pg_bsize = PNFSBLK_MAXWSIZE;
+	pgio->pg_lseg = pnfs_find_get_layout_locked(ino,
+						req_offset(req),
+						req->wb_bytes,
+						IOMODE_RW);
+	spin_unlock(&ino->i_lock);
+}
+
 static const struct nfs_pageio_ops bl_pg_read_ops = {
-	.pg_init = pnfs_generic_pg_init_read,
+	.pg_init = bl_pg_init_read,
 	.pg_test = pnfs_generic_pg_test,
 	.pg_doio = pnfs_generic_pg_readpages,
 };
 
 static const struct nfs_pageio_ops bl_pg_write_ops = {
-	.pg_init = pnfs_generic_pg_init_write,
+	.pg_init = bl_pg_init_write,
 	.pg_test = pnfs_generic_pg_test,
 	.pg_doio = pnfs_generic_pg_writepages,
 };