[PATCH 6/7] btrfs: add helper btrfs_num_devices() to deduce num_devices

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

When the replace is running the fs_devices::num_devices also includes
the replace device, however in some operations like device delete and
balance it needs the actual num_devices without the repalce devices, so
now the function btrfs_num_devices() just provides that.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
v2: add comments. Thanks Nikolay.

 fs/btrfs/volumes.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0f4c512aa6b4..1c0b56374992 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1844,6 +1844,21 @@ void btrfs_assign_next_active_device(struct btrfs_fs_info *fs_info,
 		fs_info->fs_devices->latest_bdev = next_device->bdev;
 }
 
+/* Returns btrfs_fs_devices::num_devices excluding replace device if any */
+static inline u64 btrfs_num_devices(struct btrfs_fs_info *fs_info)
+{
+	u64 num_devices = fs_info->fs_devices->num_devices;
+
+	btrfs_dev_replace_read_lock(&fs_info->dev_replace);
+	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
+		WARN_ON(num_devices < 1);
+		num_devices--;
+	}
+	btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+
+	return num_devices;
+}
+
 int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
 		u64 devid)
 {
@@ -1857,13 +1872,7 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
 
 	mutex_lock(&uuid_mutex);
 
-	num_devices = fs_devices->num_devices;
-	btrfs_dev_replace_read_lock(&fs_info->dev_replace);
-	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
-		WARN_ON(num_devices < 1);
-		num_devices--;
-	}
-	btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+	num_devices = btrfs_num_devices(fs_info);
 
 	ret = btrfs_check_raid_min_devices(fs_info, num_devices - 1);
 	if (ret)
@@ -3723,13 +3732,8 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
 		}
 	}
 
-	num_devices = fs_info->fs_devices->num_devices;
-	btrfs_dev_replace_read_lock(&fs_info->dev_replace);
-	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
-		WARN_ON(num_devices < 1);
-		num_devices--;
-	}
-	btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+	num_devices = btrfs_num_devices(fs_info);
+
 	allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE | BTRFS_BLOCK_GROUP_DUP;
 	if (num_devices > 1)
 		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
-- 
2.7.0