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    Subject[patch 076/100] SCSI: sg: fix q->queue_lock on scsi_error_handler path
    -stable review patch.  If anyone has any objections, please let us know.
    ---------------------

    From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

    upstream commit: 015640edb1f346e0b2eda703587c4cd1c310ec1d

    sg_rq_end_io() is called via rq->end_io. In some rare cases,
    sg_rq_end_io calls blk_put_request/blk_rq_unmap_user (when a program
    issuing a command has gone before the command completion; e.g. by
    interrupting a program issuing a command before the command
    completes).

    We can't call blk_put_request/blk_rq_unmap_user in interrupt so the
    commit c96952ed7031e7c576ecf90cf95b8ec099d5295a uses
    execute_in_process_context().

    The problem is that scsi_error_handler() calls rq->end_io too. We
    can't call blk_put_request/blk_rq_unmap_user too in this path (we hold
    q->queue_lock).

    To avoid the above problem, in these rare cases, this patch always
    uses schedule_work() instead of execute_in_process_context().

    Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    Acked-by: Douglas Gilbert <dgilbert@interlog.com>
    Cc: Stable Tree <stable@kernel.org>
    Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
    Signed-off-by: Chris Wright <chrisw@sous-sol.org>
    ---
    drivers/scsi/sg.c | 9 ++++++---
    1 file changed, 6 insertions(+), 3 deletions(-)

    --- a/drivers/scsi/sg.c
    +++ b/drivers/scsi/sg.c
    @@ -1323,8 +1323,10 @@ static void sg_rq_end_io(struct request
    wake_up_interruptible(&sfp->read_wait);
    kill_fasync(&sfp->async_qp, SIGPOLL, POLL_IN);
    kref_put(&sfp->f_ref, sg_remove_sfp);
    - } else
    - execute_in_process_context(sg_rq_end_io_usercontext, &srp->ew);
    + } else {
    + INIT_WORK(&srp->ew.work, sg_rq_end_io_usercontext);
    + schedule_work(&srp->ew.work);
    + }
    }

    static struct file_operations sg_fops = {
    @@ -2134,7 +2136,8 @@ static void sg_remove_sfp(struct kref *k
    write_unlock_irqrestore(&sg_index_lock, iflags);
    wake_up_interruptible(&sdp->o_excl_wait);

    - execute_in_process_context(sg_remove_sfp_usercontext, &sfp->ew);
    + INIT_WORK(&sfp->ew.work, sg_remove_sfp_usercontext);
    + schedule_work(&sfp->ew.work);
    }

    static int


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