This series introduces native SCSI multipath support. It is intended as an alternative to dm-mpath.
This support aims to provide a multipath-enabled SCSI block device/ gendisk. For a SCSI device to support native multipath, either of the following conditions must be satisfied: a. unique ID in VPD page 83 and ALUA support and scsi_multipath modparam enabled b. unique ID in VPD page 83 and scsi_multipath_always modparam enabled This series does not support ALUA. That is because the initial upfront work here is very large, and detangling the ALUA support from SCSI DH code is a lot effort at this point. ALUA support will be added once consensus is agreed on for other aspects of the design. New classes of devices are added: - scsi_mpath_device - scsi_mpath_disk These are required since a multipath scsi_device has no common scsi host. An example of the sysfs files and directories for these new classes is as follows: $ ls -l /sys/class/scsi_mpath_device/0/ total 0 -rw-r--r-- 1 root root 4096 Feb 25 11:59 iopolicy drwxr-xr-x 2 root root 0 Feb 25 11:59 multipath drwxr-xr-x 2 root root 0 Feb 25 11:59 power lrwxrwxrwx 1 root root 0 Feb 25 11:59 subsystem -> ../../../../class/scsi_mpath_device -rw-r--r-- 1 root root 4096 Feb 25 11:58 uevent -r--r--r-- 1 root root 4096 Feb 25 11:59 wwid $ ls -l /sys/class/scsi_mpath_device/0/multipath/ total 0 lrwxrwxrwx 1 root root 0 Feb 25 11:59 8:0:0:0 -> ../../../../platform/host8/session1/target8:0:0/8:0:0:0 lrwxrwxrwx 1 root root 0 Feb 25 11:59 9:0:0:0 -> ../../../../platform/host9/session2/target9:0:0/9:0:0:0 $ cat /sys/class/scsi_mpath_device/0/wwid naa.600140505200a986f0043c9afa1fd077 $ cat /sys/class/scsi_mpath_device/0/iopolicy numa $ $ ls -l /sys/class/scsi_mpath_disk/0/ total 0 drwxr-xr-x 2 root root 0 Feb 25 12:00 power drwxr-xr-x 11 root root 0 Feb 25 11:58 sdc lrwxrwxrwx 1 root root 0 Feb 25 11:58 subsystem -> ../../../../class/scsi_mpath_disk -rw-r--r-- 1 root root 4096 Feb 25 11:58 uevent $ ls -l /sys/class/scsi_mpath_disk/0/sdc/multipath/ total 0 lrwxrwxrwx 1 root root 0 Feb 25 12:00 sdc:0 -> ../../../../../platform/host8/session1/target8:0:0/8:0:0:0/block/sdc:0 lrwxrwxrwx 1 root root 0 Feb 25 12:00 sdc:1 -> ../../../../../platform/host9/session2/target9:0:0/9:0:0:0/block/sdc:1 $ ls -l /dev/sdc brw-rw---- 1 root disk 8, 32 Feb 25 11:58 /dev/sdc The scsi_device and scsi_disk classes otherwise remain unmodified. However, the per-path block device is hidden in /dev/. Furthermore, multipathed block devices have a new naming scheme, sdX:Y, where X is the scsi multipath device index and Y is the path index. I am not too happy about the naming/indexing of the new devices, so suggestions welcome for alternatives. No multipath sg support is added. We still have a per-path sg device. Since the SCSI block device is multipath enabled, we can access multipathed scsi_ioctl() through that block device. For failover, we take the approach of cloning bio's and re-submitting them in full. Series also available at https://github.com/johnpgarry/linux/commits/scsi-multipath-pre-7.0-upstream/ John Garry (24): scsi: core: add SCSI_MAX_QUEUE_DEPTH scsi-multipath: introduce basic SCSI device support scsi-multipath: introduce scsi_device head structure scsi-multipath: introduce scsi_mpath_device_class scsi-multipath: provide sysfs link from to scsi_device scsi-multipath: support iopolicy scsi-multipath: clone each bio scsi-multipath: clear path when decide is blocked scsi-multipath: failover handling scsi-multipath: add scsi_mpath_{start,end}_request() scsi-multipath: add scsi_mpath_ioctl() scsi-multipath: provide callbacks for path state scsi-multipath: set disk device_groups scsi-multipath: add PR support scsi: sd: refactor PR ops scsi: sd: add multipath disk class scsi: sd: add sd_mpath_{start,end}_command() scsi: sd: add sd_mpath_ioctl() scsi: sd: add multipath PR support scsi: sd: add sd_mpath_to_disk() scsi: sd: support multipath disk scsi: sd: add mpath_dev file scsi: sd: add mpath_numa_nodes dev attribute scsi: sd: add mpath_queue_depth dev attribute drivers/scsi/Kconfig | 10 + drivers/scsi/Makefile | 1 + drivers/scsi/scsi.c | 10 +- drivers/scsi/scsi_error.c | 12 + drivers/scsi/scsi_lib.c | 16 +- drivers/scsi/scsi_multipath.c | 789 ++++++++++++++++++++++++++++++++++ drivers/scsi/scsi_priv.h | 2 + drivers/scsi/scsi_scan.c | 4 + drivers/scsi/scsi_sysfs.c | 10 + drivers/scsi/sd.c | 731 +++++++++++++++++++++++++++++-- drivers/scsi/sd.h | 3 + include/scsi/scsi.h | 1 + include/scsi/scsi_cmnd.h | 5 + include/scsi/scsi_device.h | 2 + include/scsi/scsi_driver.h | 8 + include/scsi/scsi_multipath.h | 156 +++++++ 16 files changed, 1720 insertions(+), 40 deletions(-) create mode 100644 drivers/scsi/scsi_multipath.c create mode 100644 include/scsi/scsi_multipath.h -- 2.43.5
