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 relies on reading sdev->access_state to get path information. This path information would be provided by ALUA. ALUA support which does not rely on device handlers has already been discussed at https://lore.kernel.org/linux-scsi/[email protected]/ and support will be added in the next phase. 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/scsi_mpath_device0/ 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 vpd_id $ ls -l /sys/class/scsi_mpath_device/scsi_mpath_device0/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/scsi_mpath_device0/vpd_id naa.600140505200a986f0043c9afa1fd077 $ cat /sys/class/scsi_mpath_device/scsi_mpath_device0/iopolicy numa $ $ ls -l /sys/class/scsi_mpath_disk/scsi_mpath_disk0/ 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/scsi_mpath_disk0/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. 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 (for failover errors). Full series also available at https://github.com/johnpgarry/linux/commits/scsi-multipath-pre-7.1-upstream-v2/ Differences to v1 (apart from porting changes for v2 libmultiapth): - drop SCSI_MAX_QUEUE_DEPTH and reduce bioset size (Benjamin) - increase SCSI_MPATH_DEVICE_ID_LEN (Benjamin) - mark config SCSI_MULTIPATH as experimental (Benjamin) - combine modparams (Hannes) - rename wwid sysfs file to vpd_id (Hannes) - return umode_t from scsi_multipath_sysfs_attr_visible() (Benjamin) - use DEFINE_SYSFS_GROUP_VISIBLE() (Benjamin) - fix scsi_mpath_end_request() and blk stats (Benjamin) - change scsi_mpath_device and scsi_mpath_disk device naming (Hannes) - change locking in scsi_mpath_dev_alloc() and sd_mpath_probe() (Benjamin) - drop struct scsi_mpath_clone_bio (Benjamin) - don't use scsi_mpath_clone_bio() -> bio_alloc_clone(GFP_NOWAIT) (Benjamin) - don't use BIOSET_NEED_BVECS for bioset_init() (Benjamin) - drop PR support (problems explained by Benjamin) - drop failover handling in mpath bio completion (Benjamin) - use sdev->access_state in scsi_mpath_is_optimized() - count queue depth per shost - delayed disk removal support John Garry (18): scsi-multipath: introduce basic SCSI device support scsi-multipath: introduce scsi_device head structure 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: provide callbacks for path state scsi-multipath: add scsi_mpath_get_nr_active() scsi-multipath: add scsi_mpath_{start,end}_request() scsi-multipath: block PR commands scsi-multipath: add delayed disk removal support scsi: sd: add multipath disk class scsi: sd: support multipath disk scsi: sd: add multipath disk attr groups 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 | 8 +- drivers/scsi/scsi_lib.c | 15 + drivers/scsi/scsi_multipath.c | 658 ++++++++++++++++++++++++++++++++++ drivers/scsi/scsi_scan.c | 4 + drivers/scsi/scsi_sysfs.c | 10 + drivers/scsi/sd.c | 560 +++++++++++++++++++++++++++-- drivers/scsi/sd.h | 3 + include/scsi/scsi_cmnd.h | 5 + include/scsi/scsi_device.h | 2 + include/scsi/scsi_driver.h | 4 + include/scsi/scsi_host.h | 4 + include/scsi/scsi_multipath.h | 113 ++++++ 14 files changed, 1376 insertions(+), 21 deletions(-) create mode 100644 drivers/scsi/scsi_multipath.c create mode 100644 include/scsi/scsi_multipath.h -- 2.43.5
