• Linus Walleij's avatar
    mmc: core: Allocate per-request data using the block layer core · 304419d8
    Linus Walleij authored
    The mmc_queue_req is a per-request state container the MMC core uses
    to carry bounce buffers, pointers to asynchronous requests and so on.
    Currently allocated as a static array of objects, then as a request
    comes in, a mmc_queue_req is assigned to it, and used during the
    lifetime of the request.
    
    This is backwards compared to how other block layer drivers work:
    they usally let the block core provide a per-request struct that get
    allocated right beind the struct request, and which can be obtained
    using the blk_mq_rq_to_pdu() helper. (The _mq_ infix in this function
    name is misleading: it is used by both the old and the MQ block
    layer.)
    
    The per-request struct gets allocated to the size stored in the queue
    variable .cmd_size initialized using the .init_rq_fn() and
    cleaned up using .exit_rq_fn().
    
    The block layer code makes the MMC core rely on this mechanism to
    allocate the per-request mmc_queue_req state container.
    
    Doing this make a lot of complicated queue handling go away. We only
    need to keep the .qnct that keeps count of how many request are
    currently being processed by the MMC layer. The MQ block layer will
    replace also this once we transition to it.
    
    Doing this refactoring is necessary to move the ioctl() operations
    into custom block layer requests tagged with REQ_OP_DRV_[IN|OUT]
    instead of the custom code using the BigMMCHostLock that we have
    today: those require that per-request data be obtainable easily from
    a request after creating a custom request with e.g.:
    
    struct request *rq = blk_get_request(q, REQ_OP_DRV_IN, __GFP_RECLAIM);
    struct mmc_queue_req *mq_rq = req_to_mq_rq(rq);
    
    And this is not possible with the current construction, as the request
    is not immediately assigned the per-request state container, but
    instead it gets assigned when the request finally enters the MMC
    queue, which is way too late for custom requests.
    Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
    [Ulf: Folded in the fix to drop a call to blk_cleanup_queue()]
    Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
    Tested-by: default avatarHeiner Kallweit <hkallweit1@gmail.com>
    304419d8
block.c 57 KB