[PATCH 1/2 v14] btrfs: refactor btrfs_free_stale_devices() to get return value

[Anand Jain <anand.jain@oracle.com>]

Preparatory patch to add forget cli.

Re-factors btrfs_free_stale_devices() to obtain return status. As
this function can fail if it can't find the given path (returns -ENOENT)
or trying to delete a mounted device (returns -EBUSY).

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
v14: born.
 A split from the patch 2/2.
 Use -ENOENT.
 Document return value in the function btrfs_free_stale_devices() header.
 Adds a code comment.
 Ensures it still returns 0 if it was able to delete a device but followed
  by a path matched to a mounted device (a very remote corner case).
      if (path && ret != 0)
             ret = -EBUSY;

 fs/btrfs/volumes.c | 48 +++++++++++++++++++++++++++++++++++-------------
 1 file changed, 35 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 2576b1a379c9..d8ac63e3666d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -734,6 +734,19 @@ static void pending_bios_fn(struct btrfs_work *work)
 	run_scheduled_bios(device);
 }
 
+static bool device_path_matched(const char *path, struct btrfs_device *device)
+{
+	int found;
+
+	rcu_read_lock();
+	found = strcmp(rcu_str_deref(device->name), path);
+	rcu_read_unlock();
+
+	if (!found)
+		return true;
+	return false;
+}
+
 /*
  *  Search and remove all stale (devices which are not mounted) devices.
  *  When both inputs are NULL, it will search and release all stale devices.
@@ -741,45 +754,52 @@ static void pending_bios_fn(struct btrfs_work *work)
  *		matching this path only.
  *  skip_dev:	Optional. Will skip this device when searching for the stale
  *		devices.
+ *  Return:	0 for success or if path is NULL.
+ * 		-EBUSY if path is a mounted device.
+ * 		-ENOENT if path does not match with any device in the list.
  */
-static void btrfs_free_stale_devices(const char *path,
+static int btrfs_free_stale_devices(const char *path,
 				     struct btrfs_device *skip_device)
 {
 	struct btrfs_fs_devices *fs_devices, *tmp_fs_devices;
 	struct btrfs_device *device, *tmp_device;
+	int ret;
+
+	if (path)
+		ret = -ENOENT;
+	else
+		ret = 0;
 
 	list_for_each_entry_safe(fs_devices, tmp_fs_devices, &fs_uuids, fs_list) {
+
 		mutex_lock(&fs_devices->device_list_mutex);
-		if (fs_devices->opened) {
-			mutex_unlock(&fs_devices->device_list_mutex);
-			continue;
-		}
 
 		list_for_each_entry_safe(device, tmp_device,
 					 &fs_devices->devices, dev_list) {
-			int not_found = 0;
 
 			if (skip_device && skip_device == device)
 				continue;
 			if (path && !device->name)
 				continue;
-
-			rcu_read_lock();
-			if (path)
-				not_found = strcmp(rcu_str_deref(device->name),
-						   path);
-			rcu_read_unlock();
-			if (not_found)
+			if (path && !device_path_matched(path, device))
 				continue;
+			if (fs_devices->opened) {
+				/* if already deleted a device return 0 */
+				if (path && ret != 0)
+					ret = -EBUSY;
+				break;
+			}
 
 			/* delete the stale device */
 			fs_devices->num_devices--;
 			list_del(&device->dev_list);
 			btrfs_free_device(device);
 
+			ret = 0;
 			if (fs_devices->num_devices == 0)
 				break;
 		}
+
 		mutex_unlock(&fs_devices->device_list_mutex);
 		if (fs_devices->num_devices == 0) {
 			btrfs_sysfs_remove_fsid(fs_devices);
@@ -787,6 +807,8 @@ static void btrfs_free_stale_devices(const char *path,
 			free_fs_devices(fs_devices);
 		}
 	}
+
+	return ret;
 }
 
 static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
-- 
1.8.3.1