Re: [PATCH] btrfs: remove BTRFS_FS_QUOTA_DISABLING flag

["Misono, Tomohiro" <misono.tomohiro@jp.fujitsu.com>]

Sorry, this patch contains leading spaces, I will resend this soon.

On 2017/08/30 10:51, Misono, Tomohiro wrote:
> Currently, "btrfs quota enable" would fail after "btrfs quota disable" on
> the first time with syslog output "qgroup_rescan_init failed with -22", but
> it would succeed on the second time.
> 
> When "quota disable" is called, BTRFS_FS_QUOTA_DISABLING flag bit will be
> set in fs_info->flags in btrfs_quota_disable(), but it will not be droppd
> in btrfs_run_qgroups() (which is called in btrfs_commit_transaction())
> because quota_root has already been freed. If "quota enable" is called
> after that, both BTRFS_FS_QUOTA_DISABLING and BTRFS_FS_QUOTA_ENABLED flag
> would be dropped in the btrfs_run_qgroups() since quota_root is not NULL.
> This leads to the failure of "quota enable" on the first time.
> 
> BTRFS_FS_QUOTA_DISABLING flag is not used outside of "quota disable"
> context and is equivalent to whether quota_root is NULL or not.
> btrfs_run_qgroups() checks whether quota_root is NULL or not in the first
> place.
> 
> So, let's remove BTRFS_FS_QUOTA_DISABLING flag.
> 
> Signed-off-by: Tomohiro Misono <misono.tomohiro@jp.fujitsu.com>
> ---
>   fs/btrfs/ctree.h  | 1 -
>   fs/btrfs/qgroup.c | 4 ----
>   2 files changed, 5 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 3f3eb7b..49501c0 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -709,7 +709,6 @@ struct btrfs_delayed_root;
>   #define BTRFS_FS_OPEN				5
>   #define BTRFS_FS_QUOTA_ENABLED			6
>   #define BTRFS_FS_QUOTA_ENABLING			7
> -#define BTRFS_FS_QUOTA_DISABLING		8
>   #define BTRFS_FS_UPDATE_UUID_TREE_GEN		9
>   #define BTRFS_FS_CREATING_FREE_SPACE_TREE	10
>   #define BTRFS_FS_BTREE_ERR			11
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index 4ce351e..f0b111e 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -807,7 +807,6 @@ static int btrfs_clean_quota_tree(struct 
> btrfs_trans_handle *trans,
>   	}
>   	ret = 0;
>   out:
> -	set_bit(BTRFS_FS_QUOTA_DISABLING, &root->fs_info->flags);
>   	btrfs_free_path(path);
>   	return ret;
>   }
> @@ -954,7 +953,6 @@ int btrfs_quota_disable(struct btrfs_trans_handle 
> *trans,
>   	if (!fs_info->quota_root)
>   		goto out;
>   	clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
> -	set_bit(BTRFS_FS_QUOTA_DISABLING, &fs_info->flags);
>   	btrfs_qgroup_wait_for_completion(fs_info, false);
>   	spin_lock(&fs_info->qgroup_lock);
>   	quota_root = fs_info->quota_root;
> @@ -2087,8 +2085,6 @@ int btrfs_run_qgroups(struct btrfs_trans_handle 
> *trans,
> 
>   	if (test_and_clear_bit(BTRFS_FS_QUOTA_ENABLING, &fs_info->flags))
>   		set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
> -	if (test_and_clear_bit(BTRFS_FS_QUOTA_DISABLING, &fs_info->flags))
> -		clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
> 
>   	spin_lock(&fs_info->qgroup_lock);
>   	while (!list_empty(&fs_info->dirty_qgroups)) {
>