linux-kernel - Re: [PATCH] btrfs: Allow read-only mount with corrupted extent tree

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Message-ID: <CAOE4rSySx3fcRkvSMHEwpGVMFTOCeirw9owCu+9YDcLPzhsV9A@mail.gmail.com>
Date:   Wed, 21 Apr 2021 19:00:51 +0300
From:   Dāvis Mosāns <davispuh@...il.com>
To:     Btrfs BTRFS <linux-btrfs@...r.kernel.org>
Cc:     clm@...com, Josef Bacik <josef@...icpanda.com>, dsterba@...e.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Zygo Blaxell <ce3g8jdj@...il.furryterror.org>
Subject: Re: [PATCH] btrfs: Allow read-only mount with corrupted extent tree

svētd., 2021. g. 21. marts, plkst. 23:46 — lietotājs Dāvis Mosāns
(<davispuh@...il.com>) rakstīja:
>
> Currently if there's any corruption at all in extent tree
> (eg. even single bit) then mounting will fail with:
> "failed to read block groups: -5" (-EIO)
> It happens because we immediately abort on first error when
> searching in extent tree for block groups.
>
> Now with this patch if `ignorebadroots` option is specified
> then we handle such case and continue by removing already
> created block groups and creating dummy block groups.
>
> Signed-off-by: Dāvis Mosāns <davispuh@...il.com>
> ---
>  fs/btrfs/block-group.c | 20 ++++++++++++++++++++
>  fs/btrfs/disk-io.c     |  4 ++--
>  fs/btrfs/disk-io.h     |  2 ++
>  3 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index 48ebc106a606..f485cf14c2f8 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -2048,6 +2048,26 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
>         ret = check_chunk_block_group_mappings(info);
>  error:
>         btrfs_free_path(path);
> +
> +       if (ret == -EIO && btrfs_test_opt(info, IGNOREBADROOTS)) {
> +
> +               if (btrfs_super_log_root(info->super_copy) != 0) {
> +                       btrfs_warn(info, "Ignoring tree-log replay due to extent tree corruption!");
> +                       btrfs_set_super_log_root(info->super_copy, 0);
> +               }
> +
> +               btrfs_put_block_group_cache(info);
> +               btrfs_stop_all_workers(info);
> +               btrfs_free_block_groups(info);
> +               ret = btrfs_init_workqueues(info, NULL);
> +               if (ret)
> +                       return ret;
> +               ret = btrfs_init_space_info(info);
> +               if (ret)
> +                       return ret;
> +               return fill_dummy_bgs(info);
> +       }
> +
>         return ret;
>  }
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 07a2b4f69b10..dc744f76d075 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -1955,7 +1955,7 @@ static int read_backup_root(struct btrfs_fs_info *fs_info, u8 priority)
>  }
>
>  /* helper to cleanup workers */
> -static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
> +void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
>  {
>         btrfs_destroy_workqueue(fs_info->fixup_workers);
>         btrfs_destroy_workqueue(fs_info->delalloc_workers);
> @@ -2122,7 +2122,7 @@ static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info)
>         mutex_init(&fs_info->qgroup_rescan_lock);
>  }
>
> -static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
> +int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
>                 struct btrfs_fs_devices *fs_devices)
>  {
>         u32 max_active = fs_info->thread_pool_size;
> diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
> index e45057c0c016..f9bfcba86a04 100644
> --- a/fs/btrfs/disk-io.h
> +++ b/fs/btrfs/disk-io.h
> @@ -137,6 +137,8 @@ int btrfs_find_free_objectid(struct btrfs_root *root, u64 *objectid);
>  int btrfs_find_highest_objectid(struct btrfs_root *root, u64 *objectid);
>  int __init btrfs_end_io_wq_init(void);
>  void __cold btrfs_end_io_wq_exit(void);
> +void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info);
> +int btrfs_init_workqueues(struct btrfs_fs_info *fs_info, struct btrfs_fs_devices *fs_devices);
>
>  #ifdef CONFIG_DEBUG_LOCK_ALLOC
>  void btrfs_set_buffer_lockdep_class(u64 objectid,
> --
> 2.30.2
>

Ping? Could anyone take a look?