• Goldwyn Rodrigues's avatar
    block: return on congested block device · 03a07c92
    Goldwyn Rodrigues authored
    A new bio operation flag REQ_NOWAIT is introduced to identify bio's
    orignating from iocb with IOCB_NOWAIT. This flag indicates
    to return immediately if a request cannot be made instead
    of retrying.
    
    Stacked devices such as md (the ones with make_request_fn hooks)
    currently are not supported because it may block for housekeeping.
    For example, an md can have a part of the device suspended.
    For this reason, only request based devices are supported.
    In the future, this feature will be expanded to stacked devices
    by teaching them how to handle the REQ_NOWAIT flags.
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Reviewed-by: default avatarJens Axboe <axboe@kernel.dk>
    Signed-off-by: default avatarGoldwyn Rodrigues <rgoldwyn@suse.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    03a07c92
direct-io.c 38.4 KB