On Thu, 25 Jul 2013 15:13:40 -0400, Josef Bacik wrote:
> A user reported a panic when running with autodefrag and deleting snapshots.
> This is because we could end up trying to add the root to the dead roots list
> twice. To fix this check to see if we are empty before adding ourselves to the
> dead roots list. Thanks,
>
> Signed-off-by: Josef Bacik <jbacik@xxxxxxxxxxxx>
Tested-by: Stefan Behrens <sbehrens@xxxxxxxxxxxxxxxx>
The patch eliminates the crash. The question still is whether the double addition to the list is an indication for a problem and this patch just hides that there is a problem.
> ---
> fs/btrfs/transaction.c | 8 ++++----
> fs/btrfs/transaction.h | 2 +-
> 2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index 61a5c2c..18f7e71 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -983,12 +983,12 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
> * a dirty root struct and adds it into the list of dead roots that need to
> * be deleted
> */
> -int btrfs_add_dead_root(struct btrfs_root *root)
> +void btrfs_add_dead_root(struct btrfs_root *root)
> {
> spin_lock(&root->fs_info->trans_lock);
> - list_add_tail(&root->root_list, &root->fs_info->dead_roots);
> + if (list_empty(&root->root_list))
> + list_add_tail(&root->root_list, &root->fs_info->dead_roots);
> spin_unlock(&root->fs_info->trans_lock);
> - return 0;
> }
>
> /*
> @@ -1925,7 +1925,7 @@ int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
> }
> root = list_first_entry(&fs_info->dead_roots,
> struct btrfs_root, root_list);
> - list_del(&root->root_list);
> + list_del_init(&root->root_list);
> spin_unlock(&fs_info->trans_lock);
>
> pr_debug("btrfs: cleaner removing %llu\n",
> diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
> index 005b037..defbc42 100644
> --- a/fs/btrfs/transaction.h
> +++ b/fs/btrfs/transaction.h
> @@ -143,7 +143,7 @@ int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid);
> int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
> struct btrfs_root *root);
>
> -int btrfs_add_dead_root(struct btrfs_root *root);
> +void btrfs_add_dead_root(struct btrfs_root *root);
> int btrfs_defrag_root(struct btrfs_root *root);
> int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root);
> int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
>
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