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RDMA/srp: Increase max_segment_size

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The default behavior of the SCSI core is to set the block layer request
queue parameter max_segment_size to 64 KB. That means that elements of
scatterlists are limited to 64 KB. Since RDMA adapters support larger
sizes, increase max_segment_size for the SRP initiator.

Notes:
- The SCSI max_segment_size parameter was introduced in kernel v5.0. See
  also commit 50c2e9107f ("scsi: introduce a max_segment_size
  host_template parameters").
- Some other block drivers already set max_segment_size to UINT_MAX,
  e.g. nbd and rbd.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Bart Van Assche 2019-01-22 10:25:20 -08:00 committed by Jason Gunthorpe
parent db421a5499
commit 0b5cb3300a
2 changed files with 14 additions and 0 deletions
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1
drivers/infiniband/ulp/srp/ib_srp.c
View File

@ -3823,6 +3823,7 @@ static ssize_t srp_create_target(struct device *dev,
target_host->max_id = 1;
target_host->max_lun = -1LL;
target_host->max_cmd_len = sizeof ((struct srp_cmd *) (void *) 0L)->cdb;
target_host->max_segment_size = ib_dma_max_seg_size(ibdev);
target = host_to_target(target_host);

13
include/rdma/ib_verbs.h
View File

@ -3715,6 +3715,19 @@ static inline unsigned int ib_sg_dma_len(struct ib_device *dev,
return sg_dma_len(sg);
}
/**
* ib_dma_max_seg_size - Return the size limit of a single DMA transfer
* @dev: The device to query
*
* The returned value represents a size in bytes.
*/
static inline unsigned int ib_dma_max_seg_size(struct ib_device *dev)
{
struct device_dma_parameters *p = dev->dma_device->dma_parms;
return p ? p->max_segment_size : UINT_MAX;
}
/**
* ib_dma_sync_single_for_cpu - Prepare DMA region to be accessed by CPU
* @dev: The device for which the DMA address was created