nfs_page_group_lock cleanup

index 9425118..38eaf83 100644
@@ -145,13 +145,14 @@ static int nfs_wait_bit_uninterruptible(void *word)
 /*
  * nfs_page_group_lock - lock the head of the page group
  * @req - request in group that is to be locked
+ * @nonblock - if true don't block waiting for lock
  *
  * this lock must be held if modifying the page group list
  *
  * returns result from wait_on_bit_lock: 0 on success, < 0 on error
  */
 int
-nfs_page_group_lock(struct nfs_page *req, bool wait)
+nfs_page_group_lock(struct nfs_page *req, bool nonblock)
 {
 	struct nfs_page *head = req->wb_head;
 	int ret;

@@ -162,7 +163,7 @@ nfs_page_group_lock(struct nfs_page *req, bool wait)
 		ret = wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
 			nfs_wait_bit_uninterruptible,
 			TASK_UNINTERRUPTIBLE);
-	} while (wait && ret != 0);
+	} while (!nonblock && ret != 0);
 
 	WARN_ON_ONCE(ret > 0);
 	return ret;

@@ -226,7 +227,7 @@ bool nfs_page_group_sync_on_bit(struct nfs_page *req, unsigned int bit)
 {
 	bool ret;
 
-	nfs_page_group_lock(req, true);
+	nfs_page_group_lock(req, false);
 	ret = nfs_page_group_sync_on_bit_locked(req, bit);
 	nfs_page_group_unlock(req);
 

@@ -868,7 +869,7 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 	unsigned int offset, pgbase;
 	int ret;
 
-	ret = nfs_page_group_lock(req, false);
+	ret = nfs_page_group_lock(req, true);
 	if (ret < 0) {
 		desc->pg_error = ret;
 		return 0;

@@ -894,7 +895,7 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 			if (desc->pg_recoalesce)
 				return 0;
 			/* retry add_request for this subreq */
-			ret = nfs_page_group_lock(req, false);
+			ret = nfs_page_group_lock(req, true);
 			if (ret < 0) {
 				desc->pg_error = ret;
 				return 0;

index 1065de2..321e561 100644
@@ -241,7 +241,7 @@ static bool nfs_page_group_covers_page(struct nfs_page *req)
 	unsigned int pos = 0;
 	unsigned int len = nfs_page_length(req->wb_page);
 
-	nfs_page_group_lock(req, true);
+	nfs_page_group_lock(req, false);
 
 	do {
 		tmp = nfs_page_group_search_locked(req->wb_head, pos);

@@ -479,7 +479,7 @@ try_again:
 	}
 
 	/* lock each request in the page group */
-	ret = nfs_page_group_lock(head, false);
+	ret = nfs_page_group_lock(head, true);
 	if (ret < 0)
 		return ERR_PTR(ret);
 	subreq = head;

index 38eaf83..f393c72 100644
@@ -149,24 +149,29 @@ static int nfs_wait_bit_uninterruptible(void *word)
  *
  * this lock must be held if modifying the page group list
  *
- * returns result from wait_on_bit_lock: 0 on success, < 0 on error
+ * return 0 on success, < 0 on error: -EDELAY if nonblocking or the
+ * result from wait_on_bit_lock
+ *
+ * NOTE: calling with nonblock=false should always have set the
+ *       lock bit (see fs/buffer.c and other uses of wait_on_bit_lock
+ *       with TASK_UNINTERRUPTIBLE), so there is no need to check the result.
  */
 int
 nfs_page_group_lock(struct nfs_page *req, bool nonblock)
 {
 	struct nfs_page *head = req->wb_head;
-	int ret;
 
 	WARN_ON_ONCE(head != head->wb_head);
 
-	do {
-		ret = wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
-			nfs_wait_bit_uninterruptible,
-			TASK_UNINTERRUPTIBLE);
-	} while (!nonblock && ret != 0);
+	if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags))
+		return 0;
 
-	WARN_ON_ONCE(ret > 0);
-	return ret;
+	if (!nonblock)
+		return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
+				nfs_wait_bit_uninterruptible,
+				TASK_UNINTERRUPTIBLE);
+
+	return -EAGAIN;
 }
 
 /*

index f393c72..af707e0 100644
@@ -872,13 +872,8 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 	struct nfs_page *subreq;
 	unsigned int bytes_left = 0;
 	unsigned int offset, pgbase;
-	int ret;
 
-	ret = nfs_page_group_lock(req, true);
-	if (ret < 0) {
-		desc->pg_error = ret;
-		return 0;
-	}
+	nfs_page_group_lock(req, false);
 
 	subreq = req;
 	bytes_left = subreq->wb_bytes;

@@ -900,11 +895,7 @@ static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
 			if (desc->pg_recoalesce)
 				return 0;
 			/* retry add_request for this subreq */
-			ret = nfs_page_group_lock(req, true);
-			if (ret < 0) {
-				desc->pg_error = ret;
-				return 0;
-			}
+			nfs_page_group_lock(req, false);
 			continue;
 		}
 

index 321e561..0e3186b 100644
@@ -480,8 +480,11 @@ try_again:
 
 	/* lock each request in the page group */
 	ret = nfs_page_group_lock(head, true);
-	if (ret < 0)
+	if (ret < 0) {
+		spin_unlock(&inode->i_lock);
+		nfs_release_request(head);
 		return ERR_PTR(ret);
+	}
 	subreq = head;
 	do {
 		/*

index af707e0..e0c2e72 100644
@@ -175,6 +175,24 @@ nfs_page_group_lock(struct nfs_page *req, bool nonblock)
 }
 
 /*
+ * nfs_page_group_lock_wait - wait for the lock to clear, but don't grab it
+ * @req - a request in the group
+ *
+ * This is a blocking call to wait for the group lock to be cleared.
+ */
+void
+nfs_page_group_lock_wait(struct nfs_page *req)
+{
+	struct nfs_page *head = req->wb_head;
+
+	WARN_ON_ONCE(head != head->wb_head);
+
+	wait_on_bit(&head->wb_flags, PG_HEADLOCK,
+		nfs_wait_bit_uninterruptible,
+		TASK_UNINTERRUPTIBLE);
+}
+
+/*
  * nfs_page_group_unlock - unlock the head of the page group
  * @req - request in group that is to be unlocked
  */

index 0e3186b..f744f02 100644
@@ -478,13 +478,23 @@ try_again:
 		return NULL;
 	}
 
-	/* lock each request in the page group */
+	/* holding inode lock, so always make a non-blocking call to try the
+	 * page group lock */
 	ret = nfs_page_group_lock(head, true);
 	if (ret < 0) {
 		spin_unlock(&inode->i_lock);
+
+		if (!nonblock && ret == -EAGAIN) {
+			nfs_page_group_lock_wait(head);
+			nfs_release_request(head);
+			goto try_again;
+		}
+
 		nfs_release_request(head);
 		return ERR_PTR(ret);
 	}
+
+	/* lock each request in the page group */
 	subreq = head;
 	do {
 		/*

index 6ad2bbc..6c3e06e 100644
@@ -123,6 +123,7 @@ extern  int nfs_wait_on_request(struct nfs_page *);
 extern	void nfs_unlock_request(struct nfs_page *req);
 extern	void nfs_unlock_and_release_request(struct nfs_page *);
 extern int nfs_page_group_lock(struct nfs_page *, bool);
+extern void nfs_page_group_lock_wait(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);