[PATCH 9 06/12] btrfs: block-group: introduce btrfs_revert_block_group()

[Qu Wenruo <wqu@suse.com>]

This patch introudces a new function, btrfs_revert_block_group(), to
revert a newly created but not yet finished block group.

This is for error handling where we just called btrfs_make_block_group()
but then some error happened.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/block-group.c | 33 +++++++++++++++++++++++++++++++++
 fs/btrfs/block-group.h |  1 +
 fs/btrfs/space-info.c  | 12 +++++++++---
 3 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index bbe3c4cd28d8..dc70d3581bf0 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -2190,6 +2190,39 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans, u64 bytes_used,
 	return 0;
 }
 
+/*
+ * This is a function to revert the newly created block group, mostly for error
+ * handling.
+ *
+ * Unlike btrfs_remove_block_group(), since the new block group hasn't
+ * finished creating, it's much easier to remove it.
+ */
+void btrfs_revert_block_group(struct btrfs_trans_handle *trans, u64 bytenr)
+{
+	struct btrfs_block_group *bg;
+
+	bg = btrfs_lookup_block_group(trans->fs_info, bytenr);
+
+	if (!bg)
+		return;
+	trace_btrfs_remove_block_group(bg);
+
+	btrfs_update_space_info(bg, false, NULL);
+	unlink_block_group(bg);
+
+	btrfs_delayed_refs_rsv_release(trans->fs_info, 1);
+	list_del_init(&bg->bg_list);
+
+	del_block_group(bg);
+
+	/* One for the lookup reference */
+	btrfs_put_block_group(bg);
+
+	/* Finally free the last reference */
+	WARN_ON(refcount_read(&bg->refs) != 1);
+	btrfs_put_block_group(bg);
+}
+
 /*
  * Mark one block group RO, can be called several times for the same block
  * group.
diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index adfd7583a17b..619ca97254fb 100644
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -248,6 +248,7 @@ void btrfs_mark_bg_unused(struct btrfs_block_group *bg);
 int btrfs_read_block_groups(struct btrfs_fs_info *info);
 int btrfs_make_block_group(struct btrfs_trans_handle *trans, u64 bytes_used,
 			   u64 type, u64 chunk_offset, u64 size);
+void btrfs_revert_block_group(struct btrfs_trans_handle *trans, u64 bytenr);
 void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans);
 int btrfs_inc_block_group_ro(struct btrfs_block_group *cache,
 			     bool do_chunk_alloc);
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index c86baa331612..64b6e1d44f47 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -278,8 +278,14 @@ void btrfs_update_space_info(struct btrfs_block_group *bg, bool add,
 			found->full = 0;
 		btrfs_try_granting_tickets(info, found);
 	} else {
+		/* We get called for either removing an unused bg, or a newly
+		 * created bg.
+		 * Use their ro bit to determine which the case is.
+		 */
+		bool ro = bg->ro;
+
 		/* The block group to be removed should be empty */
-		WARN_ON(bg->used || !bg->ro);
+		WARN_ON(bg->used);
 
 		/* For removal, we need more overflow check */
 		if (btrfs_test_opt(info, ENOSPC_DEBUG)) {
@@ -288,9 +294,9 @@ void btrfs_update_space_info(struct btrfs_block_group *bg, bool add,
 			WARN_ON(found->disk_total < bg->length * factor);
 		}
 		found->total_bytes -= bg ->length;
-		found->bytes_readonly -= bg->length;
 		found->disk_total -= bg->length * factor;
-
+		if (ro)
+			found->bytes_readonly -= bg->length;
 		/*
 		 * Also remove the block group from ro list since we're
 		 * delete it from the space info accounting.
-- 
2.28.0