• Filipe Manana's avatar
    Btrfs: use global reserve when deleting unused block group after ENOSPC · 8eab77ff
    Filipe Manana authored
    
    
    It's possible to reach a state where the cleaner kthread isn't able to
    start a transaction to delete an unused block group due to lack of enough
    free metadata space and due to lack of unallocated device space to allocate
    a new metadata block group as well. If this happens try to use space from
    the global block group reserve just like we do for unlink operations, so
    that we don't reach a permanent state where starting a transaction for
    filesystem operations (file creation, renames, etc) keeps failing with
    -ENOSPC. Such an unfortunate state was observed on a machine where over
    a dozen unused data block groups existed and the cleaner kthread was
    failing to delete them due to ENOSPC error when attempting to start a
    transaction, and even running balance with a -dusage=0 filter failed with
    ENOSPC as well. Also unmounting and mounting again the filesystem didn't
    help. Allowing the cleaner kthread to use the global block reserve to
    delete the unused data block groups fixed the problem.
    Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
    Signed-off-by: default avatarJeff Mahoney <jeffm@suse.com>
    Signed-off-by: default avatarChris Mason <clm@fb.com>
    8eab77ff