scsi: zfcp: fix sysfs block queue limit output for max_segment_size
Since v2.6.35 commit 68322984 ("[SCSI] zfcp: Report scatter-gather limits to SCSI and block layer"), zfcp set dma_parms.max_segment_size == PAGE_SIZE (but without using the setter dma_set_max_seg_size()) and scsi_host_template.dma_boundary == PAGE_SIZE - 1. v5.0-rc1 commit 50c2e910 ("scsi: introduce a max_segment_size host_template parameters") introduced a new field scsi_host_template.max_segment_size. If an LLDD such as zfcp does not set it, scsi_host_alloc() uses BLK_MAX_SEGMENT_SIZE = 65536 for Scsi_Host.max_segment_size. __scsi_init_queue() announced the minimum of Scsi_Host.max_segment_size and dma_parms.max_segment_size to the block layer. For zfcp: min(65536, 4096) == 4096 which was still good. v5.0 commit a8cf59a6 ("scsi: communicate max segment size to the DMA mapping code") announces Scsi_Host.max_segment_size to the block layer and overwrites dma_parms.max_segment_size with Scsi_Host.max_segment_size. For zfcp dma_parms.max_segment_size == Scsi_Host.max_segment_size == 65536 which is also reflected in block queue limits. $ cd /sys/bus/ccw/drivers/zfcp $ cd 0.0.3c40/host5/rport-5:0-4/target5:0:4/5:0:4:10/block/sdi/queue $ cat max_segment_size 65536 Zfcp I/O still works because dma_boundary implicitly still keeps the effective max segment size <= PAGE_SIZE. However, dma_boundary does not seem visible to user space, but max_segment_size is visible and shows a misleading wrong value. Fix it and inherit the stable tag of a8cf59a6 . Devices on our bus ccw support DMA but no DMA mapping. Of multiple device types on the ccw bus, only zfcp needs dma_parms for SCSI limits. So, leave dma_parms setup in zfcp and do not move it to the bus. Signed-off-by: Steffen Maier <maier@linux.ibm.com> Fixes: 50c2e910 ("scsi: introduce a max_segment_size host_template parameters") Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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