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    Subject[PATCH 5.9 633/757] nvmet: limit passthru MTDS by BIO_MAX_PAGES
    Date
    From: Logan Gunthorpe <logang@deltatee.com>

    [ Upstream commit df06047d54276f73782c9d97882b305fca745d3f ]

    nvmet_passthru_map_sg() only supports mapping a single BIO, not a chain
    so the effective maximum transfer should also be limitted by
    BIO_MAX_PAGES (presently this works out to 1MB).

    For PCI passthru devices the max_sectors would typically be more
    limitting than BIO_MAX_PAGES, but this may not be true for all passthru
    devices.

    Fixes: c1fef73f793b ("nvmet: add passthru code to process commands")
    Suggested-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Sagi Grimberg <sagi@grimberg.me>
    Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
    Signed-off-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/nvme/target/passthru.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
    index dacfa7435d0b2..1ab88df3310f6 100644
    --- a/drivers/nvme/target/passthru.c
    +++ b/drivers/nvme/target/passthru.c
    @@ -26,7 +26,7 @@ static u16 nvmet_passthru_override_id_ctrl(struct nvmet_req *req)
    struct nvme_ctrl *pctrl = ctrl->subsys->passthru_ctrl;
    u16 status = NVME_SC_SUCCESS;
    struct nvme_id_ctrl *id;
    - u32 max_hw_sectors;
    + int max_hw_sectors;
    int page_shift;

    id = kzalloc(sizeof(*id), GFP_KERNEL);
    @@ -48,6 +48,13 @@ static u16 nvmet_passthru_override_id_ctrl(struct nvmet_req *req)
    max_hw_sectors = min_not_zero(pctrl->max_segments << (PAGE_SHIFT - 9),
    pctrl->max_hw_sectors);

    + /*
    + * nvmet_passthru_map_sg is limitted to using a single bio so limit
    + * the mdts based on BIO_MAX_PAGES as well
    + */
    + max_hw_sectors = min_not_zero(BIO_MAX_PAGES << (PAGE_SHIFT - 9),
    + max_hw_sectors);
    +
    page_shift = NVME_CAP_MPSMIN(ctrl->cap) + 12;

    id->mdts = ilog2(max_hw_sectors) + 9 - page_shift;
    --
    2.25.1


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