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    SubjectRE: [PATCH] mmc: fix host release issue after discard operation
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    Hi Ray,

    On Fri, October 25, 2013, Ray Jui wrote:
    > Under function mmc_blk_issue_rq, after an MMC discard operation,
    > the MMC request data structure may be freed in memory. Later in
    > the same function, the check of req->cmd_flags & MMC_REQ_SPECIAL_MASK
    > is dangerous and invalid. It causes the MMC host not being released
    > when it should
    >
    > This patch fixes the issue by marking the special request down before
    > the discard/flush operation
    >
    > Reported by: Harold (SoonYeal) Yang <haroldsy@broadcom.com>
    > Signed-off-by: Ray Jui <rjui@broadcom.com>
    > ---
    > drivers/mmc/card/block.c | 8 ++++++--
    > 1 file changed, 6 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
    > index 1a3163f..9e8e970 100644
    > --- a/drivers/mmc/card/block.c
    > +++ b/drivers/mmc/card/block.c
    > @@ -1954,7 +1954,7 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
    >
    > static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
    > {
    > - int ret;
    > + int ret, req_is_special = 0;
    It would be better to use boolean?

    Either, in a different way, I considered to save the cmd_flags like below.
    unsigned int cmd_flags = req ? req->cmd_flags : 0;

    Then, we could replace several 'if statement' without dereference.
    if (req && req->cmd_flags & REQ_DISCARD) -> if (cmd_flags & REQ_DISCARD)

    Just my suggestion.

    Thanks,
    Seungwon Jeon
    > struct mmc_blk_data *md = mq->data;
    > struct mmc_card *card = md->queue.card;
    > struct mmc_host *host = card->host;
    > @@ -1973,6 +1973,10 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
    > goto out;
    > }
    >
    > + /* mark special request here since req may be freed later */
    > + if (req && (req->cmd_flags & MMC_REQ_SPECIAL_MASK))
    > + req_is_special = 1;
    > +
    > mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
    > if (req && req->cmd_flags & REQ_DISCARD) {
    > /* complete ongoing async transfer before issuing discard */
    > @@ -1999,7 +2003,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
    >
    > out:
    > if ((!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) ||
    > - (req && (req->cmd_flags & MMC_REQ_SPECIAL_MASK)))
    > + req_is_special)
    > /*
    > * Release host when there are no more requests
    > * and after special request(discard, flush) is done.
    > --
    > 1.7.9.5



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