NFS: Try to join page groups before an O_DIRECT retransmission

If we have to retransmit requests, try to join their page groups
first.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/direct.c

@@ -505,6 +505,24 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter)
 	return result;
 }
 
+static void
+nfs_direct_join_group(struct list_head *list, struct inode *inode)
+{
+	struct nfs_page *req, *next;
+
+	list_for_each_entry(req, list, wb_list) {
+		if (req->wb_head != req || req->wb_this_page == req)
+			continue;
+		for (next = req->wb_this_page;
+				next != req->wb_head;
+				next = next->wb_this_page) {
+			nfs_list_remove_request(next);
+			nfs_release_request(next);
+		}
+		nfs_join_page_group(req, inode);
+	}
+}
+
 static void
 nfs_direct_write_scan_commit_list(struct inode *inode,
 				  struct list_head *list,
@@ -527,6 +545,8 @@ static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
 	nfs_init_cinfo_from_dreq(&cinfo, dreq);
 	nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);
 
+	nfs_direct_join_group(&reqs, dreq->inode);
+
 	dreq->count = 0;
 	dreq->max_count = 0;
 	list_for_each_entry(req, &reqs, wb_list)

fs/nfs/write.c

@@ -501,7 +501,7 @@ nfs_destroy_unlinked_subrequests(struct nfs_page *destroy_list,
  * the (former) group.  All subrequests are removed from any write or commit
  * lists, unlinked from the group and destroyed.
  */
-static void
+void
 nfs_join_page_group(struct nfs_page *head, struct inode *inode)
 {
 	struct nfs_page *subreq;

include/linux/nfs_page.h

@@ -141,6 +141,7 @@ extern	void nfs_unlock_request(struct nfs_page *req);
 extern	void nfs_unlock_and_release_request(struct nfs_page *);
 extern	struct nfs_page *nfs_page_group_lock_head(struct nfs_page *req);
 extern	int nfs_page_group_lock_subrequests(struct nfs_page *head);
+extern	void nfs_join_page_group(struct nfs_page *head, struct inode *inode);
 extern int nfs_page_group_lock(struct nfs_page *);
 extern void nfs_page_group_unlock(struct nfs_page *);
 extern bool nfs_page_group_sync_on_bit(struct nfs_page *, unsigned int);