Re: [PATCH 4/5] btrfs: skip log replay on orphaned roots

[Filipe Manana <fdmanana@gmail.com>]

On Fri, Dec 6, 2019 at 2:38 PM Josef Bacik <josef@toxicpanda.com> wrote:
>
> My fsstress modifications coupled with generic/475 uncovered a failure
> to mount and replay the log if we hit a orphaned root.  We do not want
> to replay the log for an orphan root, but it's completely legitimate to
> have an orphaned root with a log attached.  Fix this by simply skipping
> replaying the log.  We still need to pin it's root node so that we do
> not overwrite it while replaying other logs, as we re-read the log root
> at every stage of the replay.
>
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Looks good, thanks.

> ---
>  fs/btrfs/tree-log.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
> index 6f757361db53..4bbb4fd490b5 100644
> --- a/fs/btrfs/tree-log.c
> +++ b/fs/btrfs/tree-log.c
> @@ -6294,9 +6294,28 @@ int btrfs_recover_log_trees(struct btrfs_root *log_root_tree)
>                 wc.replay_dest = btrfs_read_fs_root_no_name(fs_info, &tmp_key);
>                 if (IS_ERR(wc.replay_dest)) {
>                         ret = PTR_ERR(wc.replay_dest);
> +
> +                       /*
> +                        * We didn't find the subvol, likely because it was
> +                        * deleted.  This is ok, simply skip this log and go to
> +                        * the next one.
> +                        *
> +                        * We need to exclude the root because we can't have
> +                        * other log replays overwriting this log as we'll read
> +                        * it back in a few more times.  This will keep our
> +                        * block from being modified, and we'll just bail for
> +                        * each subsequent pass.
> +                        */
> +                       if (ret == -ENOENT)
> +                               ret = btrfs_pin_extent_for_log_replay(fs_info,
> +                                                       log->node->start,
> +                                                       log->node->len);
>                         free_extent_buffer(log->node);
>                         free_extent_buffer(log->commit_root);
>                         kfree(log);
> +
> +                       if (!ret)
> +                               goto next;
>                         btrfs_handle_fs_error(fs_info, ret,
>                                 "Couldn't read target root for tree log recovery.");
>                         goto error;
> @@ -6328,7 +6347,6 @@ int btrfs_recover_log_trees(struct btrfs_root *log_root_tree)
>                                                   &root->highest_objectid);
>                 }
>
> -               key.offset = found_key.offset - 1;
>                 wc.replay_dest->log_root = NULL;
>                 free_extent_buffer(log->node);
>                 free_extent_buffer(log->commit_root);
> @@ -6336,9 +6354,10 @@ int btrfs_recover_log_trees(struct btrfs_root *log_root_tree)
>
>                 if (ret)
>                         goto error;
> -
> +next:
>                 if (found_key.offset == 0)
>                         break;
> +               key.offset = found_key.offset - 1;
>         }
>         btrfs_release_path(path);
>
> --
> 2.23.0
>


-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”