[PATCH 5/6] btrfs: Make free_objectid hold the next available objectid in the root

[Nikolay Borisov <nborisov@suse.com>]

Adjust the way free_objectid is being initialized, it now stores
BTRFS_FIRST_FREE_OBJECTID rather than the, somewhat arbitrary,
BTRFS_FIRST_FREE_OBJECTID - 1. This change also has the added benefit
that now it becomes unnecessary to explicitly initialize free_objectid
for a newly create fs root.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/disk-io.c | 8 ++++----
 fs/btrfs/inode.c   | 8 ++++++--
 fs/btrfs/ioctl.c   | 4 ----
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e96103b1c5db..6a4d7ea61903 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4762,10 +4762,10 @@ int btrfs_init_root_free_objectid(struct btrfs_root *root)
 		slot = path->slots[0] - 1;
 		l = path->nodes[0];
 		btrfs_item_key_to_cpu(l, &found_key, slot);
-		root->free_objectid = max_t(u64, found_key.objectid,
-				  BTRFS_FIRST_FREE_OBJECTID - 1);
+		root->free_objectid = max_t(u64, found_key.objectid + 1,
+				  BTRFS_FIRST_FREE_OBJECTID);
 	} else {
-		root->free_objectid = BTRFS_FIRST_FREE_OBJECTID - 1;
+		root->free_objectid = BTRFS_FIRST_FREE_OBJECTID;
 	}
 	ret = 0;
 error:
@@ -4786,7 +4786,7 @@ int btrfs_get_free_objectid(struct btrfs_root *root, u64 *objectid)
 		goto out;
 	}
 
-	*objectid = ++root->free_objectid;
+	*objectid = root->free_objectid++;
 	ret = 0;
 out:
 	mutex_unlock(&root->objectid_mutex);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 0dee1fa29207..aea76abd83ba 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8583,9 +8583,13 @@ int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 	struct inode *inode;
 	int err;
 	u64 index = 0;
+	u64 ino;
+
+	err = btrfs_get_free_objectid(new_root, &ino);
+	if (err < 0)
+		return err;
 
-	inode = btrfs_new_inode(trans, new_root, NULL, "..", 2,
-				new_dirid, new_dirid,
+	inode = btrfs_new_inode(trans, new_root, NULL, "..", 2, ino, ino,
 				S_IFDIR | (~current_umask() & S_IRWXUGO),
 				&index);
 	if (IS_ERR(inode))
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 21c0215a0fd0..58b9a27559c0 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -724,10 +724,6 @@ static noinline int create_subvol(struct inode *dir,
 		goto fail;
 	}
 
-	mutex_lock(&new_root->objectid_mutex);
-	new_root->free_objectid = new_dirid;
-	mutex_unlock(&new_root->objectid_mutex);
-
 	/*
 	 * insert the directory item
 	 */
-- 
2.25.1