From: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx> Hello Folks, Here is a very early RFC for multipath support in the scsi layer. This patch series implements native multipath support for scsi disks devices. In this series, I am providing conceptual changes which still needs work. However, I wanted to get this RFC out to get community feedback on the direction of changes. This RFC follows NVMe multipath implementation closely for SCSI multipath. Currently, SCSI multipath only supports disk devices which advertises ALUA (Asymmetric Logical Unit Access) capability in the Inquiry response data. Patches are split as following Patch 1: Add new SCSI multipath files and makefile changes for enabling multipath support. Patch 2: Adds changes to scsi_host structure for multipath support Patch 3: Adds error handling capability to the multipath changes. Patch 4: Wires up commpletion path for the request Patch 5: Adds sysfs hooks for displaying iopolicy and state. Patch 6: Adds changes to use ALUA handler for multipath Patch 7: Adds changes in sd driver for multipath. Patch 8: Adds changes to scsi_debug driver for ALUA testing. Here's list of TO-DO that will be addressed in next RFC version 1. Cleanup sysfs directory structure and only show first multipath device. 2. Test failover scenario with multiple disks and injecting errors with IO. 3. Test updating iopolicy while running IO and make sure path failover happens. 4. cleanup ALUA code to integrate more closely with new multipath code. 5. Performance numbers for the multipath disks. 6. PR ops are not yet handled by this series and will be added in next RFC. Thanks, Himanshu Himanshu Madhani (8): scsi: Add multipath device support scsi: create multipath capable scsi host scsi: Add error handling capability for multipath scsi: Complete multipath request scsi: Add scsi multipath sysfs hooks scsi: Add multipath suppport for device handler scsi: Add multipath disk init code for sd driver scsi_debug: Add module parameter for ALUA multipath drivers/scsi/Kconfig | 12 + drivers/scsi/Makefile | 2 + drivers/scsi/device_handler/scsi_dh_alua.c | 15 + drivers/scsi/hosts.c | 12 + drivers/scsi/scsi_debug.c | 16 +- drivers/scsi/scsi_dh.c | 3 + drivers/scsi/scsi_error.c | 8 + drivers/scsi/scsi_lib.c | 25 + drivers/scsi/scsi_multipath.c | 896 +++++++++++++++++++++ drivers/scsi/scsi_sysfs.c | 104 +++ drivers/scsi/sd.c | 83 ++ include/scsi/scsi.h | 1 + include/scsi/scsi_device.h | 64 ++ include/scsi/scsi_host.h | 7 + include/scsi/scsi_multipath.h | 86 ++ 15 files changed, 1332 insertions(+), 2 deletions(-) create mode 100644 drivers/scsi/scsi_multipath.c create mode 100644 include/scsi/scsi_multipath.h base-commit: 128faa1845a2d5b0178b986f3bd18fb38cc08cc2 -- 2.41.0.rc2
