1 files changed, 64 insertions, 3 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 93833f1dcbad..0fe9d7bf34db 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -479,6 +479,57 @@ void nfs_join_page_group(struct nfs_page *head, struct nfs_commit_info *cinfo,
 }
 
 /*
+ * nfs_unroll_locks -  unlock all newly locked reqs and wait on @req
+ * @head: head request of page group, must be holding head lock
+ * @req: request that couldn't lock and needs to wait on the req bit lock
+ *
+ * This is a helper function for nfs_lock_and_join_requests
+ * returns 0 on success, < 0 on error.
+ */
+static void
+nfs_unroll_locks(struct nfs_page *head, struct nfs_page *req)
+{
+	struct nfs_page *tmp;
+
+	/* relinquish all the locks successfully grabbed this run */
+	for (tmp = head->wb_this_page ; tmp != req; tmp = tmp->wb_this_page) {
+		if (!kref_read(&tmp->wb_kref))
+			continue;
+		nfs_unlock_and_release_request(tmp);
+	}
+}
+
+/*
+ * nfs_page_group_lock_subreq -  try to lock a subrequest
+ * @head: head request of page group
+ * @subreq: request to lock
+ *
+ * This is a helper function for nfs_lock_and_join_requests which
+ * must be called with the head request and page group both locked.
+ * On error, it returns with the page group unlocked.
+ */
+static int
+nfs_page_group_lock_subreq(struct nfs_page *head, struct nfs_page *subreq)
+{
+	int ret;
+
+	if (!kref_get_unless_zero(&subreq->wb_kref))
+		return 0;
+	while (!nfs_lock_request(subreq)) {
+		nfs_page_group_unlock(head);
+		ret = nfs_wait_on_request(subreq);
+		if (!ret)
+			ret = nfs_page_group_lock(head);
+		if (ret < 0) {
+			nfs_unroll_locks(head, subreq);
+			nfs_release_request(subreq);
+			return ret;
+		}
+	}
+	return 0;
+}
+
+/*
  * nfs_lock_and_join_requests - join all subreqs to the head req
  * @folio: the folio used to lookup the "page group" of nfs_page structures
  *
@@ -496,7 +547,7 @@ void nfs_join_page_group(struct nfs_page *head, struct nfs_commit_info *cinfo,
 static struct nfs_page *nfs_lock_and_join_requests(struct folio *folio)
 {
 	struct inode *inode = folio->mapping->host;
-	struct nfs_page *head;
+	struct nfs_page *head, *subreq;
 	struct nfs_commit_info cinfo;
 	int ret;
 
@@ -526,11 +577,21 @@ retry:
 	if (ret < 0)
 		goto out_unlock;
 
-	/* lock each request in the page group */
-	ret = nfs_page_group_lock_subrequests(head);
+	ret = nfs_page_group_lock(head);
 	if (ret < 0)
 		goto out_unlock;
 
+	/* lock each request in the page group */
+	for (subreq = head->wb_this_page;
+	     subreq != head;
+	     subreq = subreq->wb_this_page) {
+		ret = nfs_page_group_lock_subreq(head, subreq);
+		if (ret < 0)
+			goto out_unlock;
+	}
+
+	nfs_page_group_unlock(head);
+
 	nfs_init_cinfo_from_inode(&cinfo, inode);
 	nfs_join_page_group(head, &cinfo, inode);
 	return head;