nvmet: limit passthru MTDS by BIO_MAX_PAGES

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>

diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
index 56c5710..323046e 100644 (file)
--- 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;