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    Subject[PATCH AUTOSEL 5.5 515/542] nvme-pci: remove nvmeq->tags
    Date
    From: Christoph Hellwig <hch@lst.de>

    [ Upstream commit cfa27356f835dc7755192e7b941d4f4851acbcc7 ]

    There is no real need to have a pointer to the tagset in
    struct nvme_queue, as we only need it in a single place, and that place
    can derive the used tagset from the device and qid trivially. This
    fixes a problem with stale pointer exposure when tagsets are reset,
    and also shrinks the nvme_queue structure. It also matches what most
    other transports have done since day 1.

    Reported-by: Edmund Nadolski <edmund.nadolski@intel.com>
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Keith Busch <kbusch@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/nvme/host/pci.c | 23 ++++++++---------------
    1 file changed, 8 insertions(+), 15 deletions(-)

    diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
    index 365a2ddbeaa76..da392b50f73e7 100644
    --- a/drivers/nvme/host/pci.c
    +++ b/drivers/nvme/host/pci.c
    @@ -167,7 +167,6 @@ struct nvme_queue {
    /* only used for poll queues: */
    spinlock_t cq_poll_lock ____cacheline_aligned_in_smp;
    volatile struct nvme_completion *cqes;
    - struct blk_mq_tags **tags;
    dma_addr_t sq_dma_addr;
    dma_addr_t cq_dma_addr;
    u32 __iomem *q_db;
    @@ -376,29 +375,17 @@ static int nvme_admin_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,

    WARN_ON(hctx_idx != 0);
    WARN_ON(dev->admin_tagset.tags[0] != hctx->tags);
    - WARN_ON(nvmeq->tags);

    hctx->driver_data = nvmeq;
    - nvmeq->tags = &dev->admin_tagset.tags[0];
    return 0;
    }

    -static void nvme_admin_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
    -{
    - struct nvme_queue *nvmeq = hctx->driver_data;
    -
    - nvmeq->tags = NULL;
    -}
    -
    static int nvme_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
    unsigned int hctx_idx)
    {
    struct nvme_dev *dev = data;
    struct nvme_queue *nvmeq = &dev->queues[hctx_idx + 1];

    - if (!nvmeq->tags)
    - nvmeq->tags = &dev->tagset.tags[hctx_idx];
    -
    WARN_ON(dev->tagset.tags[hctx_idx] != hctx->tags);
    hctx->driver_data = nvmeq;
    return 0;
    @@ -948,6 +935,13 @@ static inline void nvme_ring_cq_doorbell(struct nvme_queue *nvmeq)
    writel(head, nvmeq->q_db + nvmeq->dev->db_stride);
    }

    +static inline struct blk_mq_tags *nvme_queue_tagset(struct nvme_queue *nvmeq)
    +{
    + if (!nvmeq->qid)
    + return nvmeq->dev->admin_tagset.tags[0];
    + return nvmeq->dev->tagset.tags[nvmeq->qid - 1];
    +}
    +
    static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
    {
    volatile struct nvme_completion *cqe = &nvmeq->cqes[idx];
    @@ -972,7 +966,7 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
    return;
    }

    - req = blk_mq_tag_to_rq(*nvmeq->tags, cqe->command_id);
    + req = blk_mq_tag_to_rq(nvme_queue_tagset(nvmeq), cqe->command_id);
    trace_nvme_sq(req, cqe->sq_head, nvmeq->sq_tail);
    nvme_end_request(req, cqe->status, cqe->result);
    }
    @@ -1572,7 +1566,6 @@ static const struct blk_mq_ops nvme_mq_admin_ops = {
    .queue_rq = nvme_queue_rq,
    .complete = nvme_pci_complete_rq,
    .init_hctx = nvme_admin_init_hctx,
    - .exit_hctx = nvme_admin_exit_hctx,
    .init_request = nvme_init_request,
    .timeout = nvme_timeout,
    };
    --
    2.20.1
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