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    Subject[PATCH 3.19.y-ckt 099/128] block: Always check queue limits for cloned requests
    Date
    3.19.8-ckt12 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Hannes Reinecke <hare@suse.de>

    commit bf4e6b4e757488dee1b6a581f49c7ac34cd217f8 upstream.

    When a cloned request is retried on other queues it always needs
    to be checked against the queue limits of that queue.
    Otherwise the calculations for nr_phys_segments might be wrong,
    leading to a crash in scsi_init_sgtable().

    To clarify this the patch renames blk_rq_check_limits()
    to blk_cloned_rq_check_limits() and removes the symbol
    export, as the new function should only be used for
    cloned requests and never exported.

    Cc: Mike Snitzer <snitzer@redhat.com>
    Cc: Ewan Milne <emilne@redhat.com>
    Cc: Jeff Moyer <jmoyer@redhat.com>
    Signed-off-by: Hannes Reinecke <hare@suse.de>
    Fixes: e2a60da74 ("block: Clean up special command handling logic")
    Acked-by: Mike Snitzer <snitzer@redhat.com>
    Signed-off-by: Jens Axboe <axboe@fb.com>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    block/blk-core.c | 21 +++++++--------------
    include/linux/blkdev.h | 1 -
    2 files changed, 7 insertions(+), 15 deletions(-)

    diff --git a/block/blk-core.c b/block/blk-core.c
    index 3ad4055..adb49b4 100644
    --- a/block/blk-core.c
    +++ b/block/blk-core.c
    @@ -1985,7 +1985,8 @@ void submit_bio(int rw, struct bio *bio)
    EXPORT_SYMBOL(submit_bio);

    /**
    - * blk_rq_check_limits - Helper function to check a request for the queue limit
    + * blk_cloned_rq_check_limits - Helper function to check a cloned request
    + * for new the queue limits
    * @q: the queue
    * @rq: the request being checked
    *
    @@ -1996,20 +1997,13 @@ EXPORT_SYMBOL(submit_bio);
    * after it is inserted to @q, it should be checked against @q before
    * the insertion using this generic function.
    *
    - * This function should also be useful for request stacking drivers
    - * in some cases below, so export this function.
    * Request stacking drivers like request-based dm may change the queue
    - * limits while requests are in the queue (e.g. dm's table swapping).
    - * Such request stacking drivers should check those requests against
    - * the new queue limits again when they dispatch those requests,
    - * although such checkings are also done against the old queue limits
    - * when submitting requests.
    + * limits when retrying requests on other queues. Those requests need
    + * to be checked against the new queue limits again during dispatch.
    */
    -int blk_rq_check_limits(struct request_queue *q, struct request *rq)
    +static int blk_cloned_rq_check_limits(struct request_queue *q,
    + struct request *rq)
    {
    - if (!rq_mergeable(rq))
    - return 0;
    -
    if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, rq->cmd_flags)) {
    printk(KERN_ERR "%s: over max size limit.\n", __func__);
    return -EIO;
    @@ -2029,7 +2023,6 @@ int blk_rq_check_limits(struct request_queue *q, struct request *rq)

    return 0;
    }
    -EXPORT_SYMBOL_GPL(blk_rq_check_limits);

    /**
    * blk_insert_cloned_request - Helper for stacking drivers to submit a request
    @@ -2041,7 +2034,7 @@ int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
    unsigned long flags;
    int where = ELEVATOR_INSERT_BACK;

    - if (blk_rq_check_limits(q, rq))
    + if (blk_cloned_rq_check_limits(q, rq))
    return -EIO;

    if (rq->rq_disk &&
    diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
    index 92f4b4b..25ac915 100644
    --- a/include/linux/blkdev.h
    +++ b/include/linux/blkdev.h
    @@ -797,7 +797,6 @@ extern void blk_rq_set_block_pc(struct request *);
    extern void blk_requeue_request(struct request_queue *, struct request *);
    extern void blk_add_request_payload(struct request *rq, struct page *page,
    unsigned int len);
    -extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);
    extern int blk_lld_busy(struct request_queue *q);
    extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
    struct bio_set *bs, gfp_t gfp_mask,
    --
    1.9.1


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