On Mon, Feb 25, 2019 at 6:58 PM David Sterba <dsterba@xxxxxxxx> wrote:
>
> The allocation happens with GFP_KERNEL after a transaction has been
> started, this can potentially cause deadlock if reclaim tries to get the
> memory by flushing filesystem data.
>
> The qgroup_ulist is not used during transaction start as the quotas are
> not yet enabled but to provide the same semantics, use a temporary
> variable and assign fs_info::qgroup_ulist as before.
>
> Signed-off-by: David Sterba <dsterba@xxxxxxxx>
> ---
> fs/btrfs/qgroup.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index c1cd5558a646..9e49d5e132b8 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -887,6 +887,7 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
> struct btrfs_key found_key;
> struct btrfs_qgroup *qgroup = NULL;
> struct btrfs_trans_handle *trans = NULL;
> + struct ulist *tmp_ulist;
> int ret = 0;
> int slot;
>
> @@ -894,6 +895,12 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
> if (fs_info->quota_root)
> goto out;
>
> + tmp_ulist = ulist_alloc(GFP_KERNEL);
> + if (!tmp_ulist) {
> + ret = -ENOMEM;
> + goto out;
> + }
tmp_ulist needs to be freed if starting the transaction below fails.
Other then that, looks good.
> +
> /*
> * 1 for quota root item
> * 1 for BTRFS_QGROUP_STATUS item
> @@ -909,12 +916,7 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
> goto out;
> }
>
> - fs_info->qgroup_ulist = ulist_alloc(GFP_KERNEL);
> - if (!fs_info->qgroup_ulist) {
> - ret = -ENOMEM;
> - btrfs_abort_transaction(trans, ret);
> - goto out;
> - }
> + fs_info->qgroup_ulist = tmp_ulist;
>
> /*
> * initially create the quota tree
> --
> 2.20.1
>
--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
